Tag Archives: Geo-engineering

Geo-engineered crops may help – and harm

To cool the world and also boost plant growth, geo-engineered crops might do the trick. But if they work by dimming the sunlight, the plants will suffer.

LONDON, 13 August, 2018 – Proposals to tackle climate change that rely on geo-engineered crops show neatly the double bind that can await remedies which try to do too much.

US researchers have cast yet another shadow over the hopes of those who think global technology could damp down global warming. A worldwide manmade sunscreen might limit distress to crops from heat extremes, but on the other hand the drop in solar radiation would be just as damaging.

The message: there is still no easy technological answer to the challenge of global warming and climate change.

Scientists report in the journal Nature that they studied two well-documented events in which nature itself conducted a form of geoengineering. One was the eruption of El Chichon in Mexico in 1982, and the other was the explosion of Pinatubo in the Philippines in 1991.

Suggesting a remedy

Pinatubo ejected a spectacular 20 million tons of sulphate aerosols into the upper atmosphere to reduce sunlight by 2.5% and to lower global average temperatures by around 0.5 C.

Such eruptions seemed to suggest a possible method for managing global warming, The deliberate release of aerosols into the stratosphere could, some scientists argued, counter the threat of global warming from ever greater emissions of greenhouse gases as a consequence of the ever more extensive combustion of fossil fuels.

And global warming certainly presents a global danger to food supplies: researchers have repeatedly shown that, as temperatures soar, crop yields suffer.

The researchers then asked the question: what happens to crops when sunlight is scattered back into space? They analysed the levels of aerosols, all the available data for solar irradiation, and the statistics for crop yields for 105 countries from 1979 to 2009, to find that as the sunlight bounced back into space in 1982 and 1991, yields from rice, soy, wheat and maize all suffered.

“Sunlight powers everything on the planet, so we must understand the possible outcomes if we are going to try to manage it”

A bit more work with computer simulations showed them that losses from reductions in sunlight would match any benefits crops might gain from a cooler climate. Intentional geo-engineering would fail to deliver the hoped-for extra food on the global table.

“Shading the planet keeps things cooler, which helps crops grow better. But plants also need sunlight to grow, so blocking sunlight can affect growth. For agriculture, the unintended impacts of solar geo-engineering are equal in magnitude to the benefits,” said lead author Jonathan Proctor, a doctoral candidate at the University of California, Berkeley.

“It’s a bit like performing an experimental surgery; the side-effects of treatment appear to be as bad as the illness.”

Researchers have repeatedly examined
geo-engineering solutions to the challenge of climate change. Humans have inadvertently warmed the planet. So surely they could intentionally cool it again with some ambitious technology, the reasoning goes.

Recurrent snags

But almost every examination of the potential benefits and handicaps of such an approach has been discouraging: either the technology won’t deliver benefits, or it could prove harmful in unexpected ways.

Partners in the latest study include Solomon Hsiang of UC Berkeley and Marshall Burke of Stanford University. In the past few years the two have looked closely at the economic and social consequences of global warming, to find that temperature increases are likely to affect many people’s incomes; that as the thermometer rises, so does the danger of social conflict, and even of depression and suicide.

“Unknown unknowns make everybody nervous when it comes to global policies, as they should,” Professor Hsiang said. “The problem in figuring out the consequences of solar geo-engineering is that we can’t do a planetary-scale experiment without actually deploying the technology.

Learning from nature

“The breakthrough here was realising that we could learn something by studying the effects of giant volcanic eruptions that geo-engineering tries to copy.”

Sunscreen by sulphate aerosol is not the only possible geo-engineering solution; and food security is not the only thing threatened by rising temperatures. The latest study is unlikely to be the end of the debate. The authors suggest more research into the human and ecological consequences of geo-engineering, both good and bad.

“The most certain way to reduce damages to crops and, in turn, people’s livelihood and well-being, is reducing carbon emissions,” Proctor said. And Professor Hsiang said: “Perhaps what is most important is that we have respect for the potential scale, power and risks of geo-engineering technologies.

“Sunlight powers everything on the planet, so we must understand the possible outcomes if we are going to try to manage it.” – Climate News Network

To cool the world and also boost plant growth, geo-engineered crops might do the trick. But if they work by dimming the sunlight, the plants will suffer.

LONDON, 13 August, 2018 – Proposals to tackle climate change that rely on geo-engineered crops show neatly the double bind that can await remedies which try to do too much.

US researchers have cast yet another shadow over the hopes of those who think global technology could damp down global warming. A worldwide manmade sunscreen might limit distress to crops from heat extremes, but on the other hand the drop in solar radiation would be just as damaging.

The message: there is still no easy technological answer to the challenge of global warming and climate change.

Scientists report in the journal Nature that they studied two well-documented events in which nature itself conducted a form of geoengineering. One was the eruption of El Chichon in Mexico in 1982, and the other was the explosion of Pinatubo in the Philippines in 1991.

Suggesting a remedy

Pinatubo ejected a spectacular 20 million tons of sulphate aerosols into the upper atmosphere to reduce sunlight by 2.5% and to lower global average temperatures by around 0.5 C.

Such eruptions seemed to suggest a possible method for managing global warming, The deliberate release of aerosols into the stratosphere could, some scientists argued, counter the threat of global warming from ever greater emissions of greenhouse gases as a consequence of the ever more extensive combustion of fossil fuels.

And global warming certainly presents a global danger to food supplies: researchers have repeatedly shown that, as temperatures soar, crop yields suffer.

The researchers then asked the question: what happens to crops when sunlight is scattered back into space? They analysed the levels of aerosols, all the available data for solar irradiation, and the statistics for crop yields for 105 countries from 1979 to 2009, to find that as the sunlight bounced back into space in 1982 and 1991, yields from rice, soy, wheat and maize all suffered.

“Sunlight powers everything on the planet, so we must understand the possible outcomes if we are going to try to manage it”

A bit more work with computer simulations showed them that losses from reductions in sunlight would match any benefits crops might gain from a cooler climate. Intentional geo-engineering would fail to deliver the hoped-for extra food on the global table.

“Shading the planet keeps things cooler, which helps crops grow better. But plants also need sunlight to grow, so blocking sunlight can affect growth. For agriculture, the unintended impacts of solar geo-engineering are equal in magnitude to the benefits,” said lead author Jonathan Proctor, a doctoral candidate at the University of California, Berkeley.

“It’s a bit like performing an experimental surgery; the side-effects of treatment appear to be as bad as the illness.”

Researchers have repeatedly examined
geo-engineering solutions to the challenge of climate change. Humans have inadvertently warmed the planet. So surely they could intentionally cool it again with some ambitious technology, the reasoning goes.

Recurrent snags

But almost every examination of the potential benefits and handicaps of such an approach has been discouraging: either the technology won’t deliver benefits, or it could prove harmful in unexpected ways.

Partners in the latest study include Solomon Hsiang of UC Berkeley and Marshall Burke of Stanford University. In the past few years the two have looked closely at the economic and social consequences of global warming, to find that temperature increases are likely to affect many people’s incomes; that as the thermometer rises, so does the danger of social conflict, and even of depression and suicide.

“Unknown unknowns make everybody nervous when it comes to global policies, as they should,” Professor Hsiang said. “The problem in figuring out the consequences of solar geo-engineering is that we can’t do a planetary-scale experiment without actually deploying the technology.

Learning from nature

“The breakthrough here was realising that we could learn something by studying the effects of giant volcanic eruptions that geo-engineering tries to copy.”

Sunscreen by sulphate aerosol is not the only possible geo-engineering solution; and food security is not the only thing threatened by rising temperatures. The latest study is unlikely to be the end of the debate. The authors suggest more research into the human and ecological consequences of geo-engineering, both good and bad.

“The most certain way to reduce damages to crops and, in turn, people’s livelihood and well-being, is reducing carbon emissions,” Proctor said. And Professor Hsiang said: “Perhaps what is most important is that we have respect for the potential scale, power and risks of geo-engineering technologies.

“Sunlight powers everything on the planet, so we must understand the possible outcomes if we are going to try to manage it.” – Climate News Network

Solar geoengineering ‘too uncertain to go ahead yet’

The world must urgently agree controls on solar geoengineering to weigh up its possible risks and benefits before deciding to go ahead, one expert says.

LONDON, 6 April, 2018 – Progress to deploy solar engineering, experimental technology designed to protect the world against the impact of the changing climate, must pause, a former United Nations climate expert says, arguing that governments need to create “effective guardrails” against any unforeseen risks.

Janos Pasztor, who served as a UN assistant secretary-general on climate change, is using a speech to Arizona State University, broadast via Facebook Live by ASU LightWorks, 6:30-8pm Arizona time (9:30pm EDT – US Eastern Daylight Time) today, to warn the world that governments are largely ignoring the fundamental question of who should control geoengineering, and how.

There are widespread misgivings, both among scientists and more widely, about geoengineering, with many regarding it as at best a strategy of last resort to help to avoid calamitous climate change.

Mr Pasztor’s warning comes as researchers prepare for what is thought to be the world’s first outdoor experiment on stratospheric aerosol injection (SAI), one type of solar geoengineering. The test is due to take place later this year over Arizona.

Pasztor heads the Carnegie Climate Geoengineering Governance Initiative (C2G2),  an initiative of the New York-based Carnegie Council for Ethics in International Affairs. The Initiative wants solar geoengineering deployment to be delayed until the risks and potential benefits are better known and governance frameworks are agreed.

“Getting this right is a challenge that affects all humanity . . . It’s critical the world addresses this issue as soon as possible”

“Some time within the next year, we may see the world’s first outdoor experiment on stratospheric aerosol injection take place here in the skies above Arizona, yet for the most part governments are not aware of, nor addressing, the profound governance issues this poses,” Mr Pasztor says.

“We urgently need an open, inclusive discussion on how the world will research and govern solar geoengineering. Otherwise we could be in danger of events overtaking society’s capacity to respond prudently and effectively.”

Solar geoengineering does not remove carbon from the atmosphere, and so it can be used only to supplement action to reduce greenhouse gas emissions: it can never replace that action. Many risks and unknowns remain, Pasztor says, including possible harm to the environment, and to justice, geopolitical concerns and governance.

With SAI aerosols are sprayed into the stratosphere to reflect the sun’s radiation and cool the earth fast. It is still in its early stages, and scientists say it will take another 15 to 20 years for the technology to be developed fully.

Too soon to decide

Any eventual full-scale deployment of technology of this sort would have planet-wide effects and pose profound ethical and governance challenges, C2G2 says. Pasztor says the risks and potential benefits of SAI are not yet understood well enough for policymakers to reach informed decisions.

This year’s planned experiment, called SCoPEx (Stratospheric Controlled Perturbation Experiment) is run by a Harvard University research group, which says the physical risks posed by the quantity of aerosols to be released during SCoPEx will be hundreds of times smaller than during a transatlantic flight by a commercial airliner.

Even so, Pasztor says, the governance of SCoPEx will probably set important precedents. “As solar geoengineering moves from the lab to outdoor experiments, crucial questions remain unanswered,” he argues.

“How does this experiment acquire legitimacy from other scientists? Do civil society groups and the public, including those located in the area of the experiment, have a say? What are the ramifications for other proposed experiments in this country or in other countries?”

Priority for cuts

So far, he says, many governments and civil society groups have shied away from the need to create governance for the new technology, or have not been aware of it. One common concern is that discussing geoengineering could distract society from concentrating on cutting carbon dioxide emissions.

Other geoengineering ideas, which may be nearing testing, include proposals to refreeze parts of the Arctic and to brighten clouds at sea.

“There’s no question we must accelerate efforts to rapidly reduce global emissions, whilst at the same time remaining open to the possibility that other approaches may also be needed if we are to limit some of the adverse impacts of global warming”, Pasztor says.

“Public policy needs to address very legitimate safety, human rights and accountability issues, as well as concern for future generations.

“Getting this right is a challenge that affects all humanity, and needs to be addressed through discussions that include all sectors of society. It’s critical the world addresses this issue as soon as possible.” – Climate News Network

The world must urgently agree controls on solar geoengineering to weigh up its possible risks and benefits before deciding to go ahead, one expert says.

LONDON, 6 April, 2018 – Progress to deploy solar engineering, experimental technology designed to protect the world against the impact of the changing climate, must pause, a former United Nations climate expert says, arguing that governments need to create “effective guardrails” against any unforeseen risks.

Janos Pasztor, who served as a UN assistant secretary-general on climate change, is using a speech to Arizona State University, broadast via Facebook Live by ASU LightWorks, 6:30-8pm Arizona time (9:30pm EDT – US Eastern Daylight Time) today, to warn the world that governments are largely ignoring the fundamental question of who should control geoengineering, and how.

There are widespread misgivings, both among scientists and more widely, about geoengineering, with many regarding it as at best a strategy of last resort to help to avoid calamitous climate change.

Mr Pasztor’s warning comes as researchers prepare for what is thought to be the world’s first outdoor experiment on stratospheric aerosol injection (SAI), one type of solar geoengineering. The test is due to take place later this year over Arizona.

Pasztor heads the Carnegie Climate Geoengineering Governance Initiative (C2G2),  an initiative of the New York-based Carnegie Council for Ethics in International Affairs. The Initiative wants solar geoengineering deployment to be delayed until the risks and potential benefits are better known and governance frameworks are agreed.

“Getting this right is a challenge that affects all humanity . . . It’s critical the world addresses this issue as soon as possible”

“Some time within the next year, we may see the world’s first outdoor experiment on stratospheric aerosol injection take place here in the skies above Arizona, yet for the most part governments are not aware of, nor addressing, the profound governance issues this poses,” Mr Pasztor says.

“We urgently need an open, inclusive discussion on how the world will research and govern solar geoengineering. Otherwise we could be in danger of events overtaking society’s capacity to respond prudently and effectively.”

Solar geoengineering does not remove carbon from the atmosphere, and so it can be used only to supplement action to reduce greenhouse gas emissions: it can never replace that action. Many risks and unknowns remain, Pasztor says, including possible harm to the environment, and to justice, geopolitical concerns and governance.

With SAI aerosols are sprayed into the stratosphere to reflect the sun’s radiation and cool the earth fast. It is still in its early stages, and scientists say it will take another 15 to 20 years for the technology to be developed fully.

Too soon to decide

Any eventual full-scale deployment of technology of this sort would have planet-wide effects and pose profound ethical and governance challenges, C2G2 says. Pasztor says the risks and potential benefits of SAI are not yet understood well enough for policymakers to reach informed decisions.

This year’s planned experiment, called SCoPEx (Stratospheric Controlled Perturbation Experiment) is run by a Harvard University research group, which says the physical risks posed by the quantity of aerosols to be released during SCoPEx will be hundreds of times smaller than during a transatlantic flight by a commercial airliner.

Even so, Pasztor says, the governance of SCoPEx will probably set important precedents. “As solar geoengineering moves from the lab to outdoor experiments, crucial questions remain unanswered,” he argues.

“How does this experiment acquire legitimacy from other scientists? Do civil society groups and the public, including those located in the area of the experiment, have a say? What are the ramifications for other proposed experiments in this country or in other countries?”

Priority for cuts

So far, he says, many governments and civil society groups have shied away from the need to create governance for the new technology, or have not been aware of it. One common concern is that discussing geoengineering could distract society from concentrating on cutting carbon dioxide emissions.

Other geoengineering ideas, which may be nearing testing, include proposals to refreeze parts of the Arctic and to brighten clouds at sea.

“There’s no question we must accelerate efforts to rapidly reduce global emissions, whilst at the same time remaining open to the possibility that other approaches may also be needed if we are to limit some of the adverse impacts of global warming”, Pasztor says.

“Public policy needs to address very legitimate safety, human rights and accountability issues, as well as concern for future generations.

“Getting this right is a challenge that affects all humanity, and needs to be addressed through discussions that include all sectors of society. It’s critical the world addresses this issue as soon as possible.” – Climate News Network

More reflectivity can cool the world

Think of reflectivity as down-to-earth geoengineering. Some simple actions could make a big difference to city life in the long hot summer.

LONDON, 14 February, 2018 – Engineering reflectivity can be a way to protect human safety during dangerous heatwaves: in the baking rural regions, put off ploughing those freshly-harvested wheat fields. And in the sweltering cities, paint the houses white, fit shiny roofs and plant pale-leafed tree species

In a word, increase reflectivity. Bounce more sunlight back into space to save lives, tempers and energy costs. It would, in effect, be local geoengineering, but without the unimaginable costs of spraying aerosols into the stratosphere, or placing solar reflectors in orbit; and without unwelcome side effects.

And it is based on the simple observation that a harvested wheat field is brighter than ploughed croplands, and that reflective roofs are less likely to absorb sunlight than dark tiles or slates.

“These measures could help to lower extreme temperatures in agricultural regions and densely populated areas by up to two to three degrees Celsius,” said Sonia Seneviratne, professor of land-climate dynamics at ETH Zurich, the Swiss federal institute of technology.

“Even this climate technique is no silver bullet; it’s just one potential tool among several others in the battle against climate change”

And her co-author Andy Pitman, of the University of New South Wales, who directs the Australian research council’s Centre of Excellence for Climate Extremes, said: “Extreme temperatures are where human and natural systems are most vulnerable. Changing the radiative properties of land helps address this issue with fewer side effects.

“This research suggests that by taking the regional approach, at least in temperate zones, policy and investment decisions can be pragmatically and affordably focused on areas of greatest need.”

The Swiss and Australian scientists report in the journal Nature Geoscience that they worked with computer models to simulate changes in the albedo of the land and the cities: albedo is the climate scientist’s word for the reflectivity of ocean, ice, desert or forest.

What the researchers found was that the higher the temperatures, the stronger the effect of enhanced albedo, or reflectivity.

Growing problem

And the big heat is on the way. Researchers have repeatedly confirmed that heat extremes pose increasing threats, especially to the megacities, urban centres with more than 10 million people.

They have also confirmed that such extremes of heat can be lethal,  especially when matched with rising humidity.

Cities in any case are more at hazard, because of the notorious urban heat island effect. Greater investment in air conditioning plant is not the answer, because it could only increase energy demand driven by fossil fuel combustion and thus raise urban temperatures even higher and increase long-term global warming even more.

So there has been more emphasis on natural responses, such as greater investment in the “urban forest” of park, garden and avenue trees to keep the urban population a little cooler.

Reducing extremes

The latest study found that large scale alteration of rural and urban albedo had no significant effect on average temperatures, and made hardly any difference to rainfall in Europe and North America. But as the thermometer soared, so did the effect: it did significantly reduce the extremes of heat.

In Asia, this form of what might be called grassroots geoengineering may not suit: monsoon rainfall fell in the simulation, and the monsoons are crucial to the economies of China and India.

“Regional radiation management can be effective, but even here we have to consider any potential effects on food production, biodiversity, CO2 absorption, recreation areas and much more,” said Professor Seneviratne.

“Even this climate technique is no silver bullet; it’s just one potential tool among several others in the battle against climate change.” – Climate News Network

Think of reflectivity as down-to-earth geoengineering. Some simple actions could make a big difference to city life in the long hot summer.

LONDON, 14 February, 2018 – Engineering reflectivity can be a way to protect human safety during dangerous heatwaves: in the baking rural regions, put off ploughing those freshly-harvested wheat fields. And in the sweltering cities, paint the houses white, fit shiny roofs and plant pale-leafed tree species

In a word, increase reflectivity. Bounce more sunlight back into space to save lives, tempers and energy costs. It would, in effect, be local geoengineering, but without the unimaginable costs of spraying aerosols into the stratosphere, or placing solar reflectors in orbit; and without unwelcome side effects.

And it is based on the simple observation that a harvested wheat field is brighter than ploughed croplands, and that reflective roofs are less likely to absorb sunlight than dark tiles or slates.

“These measures could help to lower extreme temperatures in agricultural regions and densely populated areas by up to two to three degrees Celsius,” said Sonia Seneviratne, professor of land-climate dynamics at ETH Zurich, the Swiss federal institute of technology.

“Even this climate technique is no silver bullet; it’s just one potential tool among several others in the battle against climate change”

And her co-author Andy Pitman, of the University of New South Wales, who directs the Australian research council’s Centre of Excellence for Climate Extremes, said: “Extreme temperatures are where human and natural systems are most vulnerable. Changing the radiative properties of land helps address this issue with fewer side effects.

“This research suggests that by taking the regional approach, at least in temperate zones, policy and investment decisions can be pragmatically and affordably focused on areas of greatest need.”

The Swiss and Australian scientists report in the journal Nature Geoscience that they worked with computer models to simulate changes in the albedo of the land and the cities: albedo is the climate scientist’s word for the reflectivity of ocean, ice, desert or forest.

What the researchers found was that the higher the temperatures, the stronger the effect of enhanced albedo, or reflectivity.

Growing problem

And the big heat is on the way. Researchers have repeatedly confirmed that heat extremes pose increasing threats, especially to the megacities, urban centres with more than 10 million people.

They have also confirmed that such extremes of heat can be lethal,  especially when matched with rising humidity.

Cities in any case are more at hazard, because of the notorious urban heat island effect. Greater investment in air conditioning plant is not the answer, because it could only increase energy demand driven by fossil fuel combustion and thus raise urban temperatures even higher and increase long-term global warming even more.

So there has been more emphasis on natural responses, such as greater investment in the “urban forest” of park, garden and avenue trees to keep the urban population a little cooler.

Reducing extremes

The latest study found that large scale alteration of rural and urban albedo had no significant effect on average temperatures, and made hardly any difference to rainfall in Europe and North America. But as the thermometer soared, so did the effect: it did significantly reduce the extremes of heat.

In Asia, this form of what might be called grassroots geoengineering may not suit: monsoon rainfall fell in the simulation, and the monsoons are crucial to the economies of China and India.

“Regional radiation management can be effective, but even here we have to consider any potential effects on food production, biodiversity, CO2 absorption, recreation areas and much more,” said Professor Seneviratne.

“Even this climate technique is no silver bullet; it’s just one potential tool among several others in the battle against climate change.” – Climate News Network

New risk of atmospheric aerosols as sunscreen

Using atmospheric aerosols to cut global warming is agreed to be risky. It might be even riskier to start it and then stop.

LONDON, 31 January, 2018 – Geoengineering, spraying atmospheric aerosols as the technofix answer to a warming planet, has been repeatedly denounced as dangerous by many critics. Now scientists say it could hide another hazard: once started, it might be dangerous to stop.

That is because their research shows that if this planetary sunscreen worked, and the technology was then brought to a halt, global warming would resume, at up to 10 times the speed.

And that would present even more danger for plants and animals already at risk from climate change, according to US scientists who write in the journal Nature Ecology and Evolution.

“Rapid warming after stopping would be a huge threat to the natural environment and biodiversity,” said Alan Robock, a climate scientist at Rutgers University – New Brunswick.

Huge risk

“If geoengineering ever stopped abruptly, it would be devastating, so you would have to be sure that it could be stopped gradually, and it is easy to think of scenarios that would prevent that.

“Imagine large droughts or floods around the world that could be blamed on geoengineering, and demands that it stop. Can we ever risk that?”

Almost all climate scientists argue that the proper way to control climate change is to drastically cut fossil fuel use and switch to wind, solar and water power to drive modern economies.

Even proponents of the technofix – the use of expensive technologies to screen or reflect sunlight by, for instance, spraying sulphate aerosols into the stratosphere – concede that prevention is best.

“If geoengineering ever stopped abruptly, it would be devastating, so you would have to be sure that it could be stopped gradually”

The geoengineering argument remains on the table of possibilities because, for the moment, progress towards real reduction is slow, and researchers have repeatedly warned that hopes of containing global warming, and limiting climate change, are dwindling.

So, once again, Rutgers scientists looked at ways of darkening the upper skies, and their implications. Although researchers have warned again and again of the dangers of such steps, at least one study has conceded that, in theory, the technology could be made to work.

So Professor Robock and colleagues considered the sky-spray solution again. They modelled the injection by high-flying aircraft of five million tons of sulphur dioxide into the upper atmosphere, over the equator, from 2020 to 2070. This is the annual equivalent of about one quarter of the sulphate aerosols hurled into the upper atmosphere by the eruption of Mt Pinatubo, in 1991, in the Philippines.

The sulphate clouds would spread evenly over the northern and southern hemispheres, to lower global temperatures by about 1°C, and bring them back down to the global average before the Industrial Revolution. But any halt in the programme would bring global warming back much faster than if geoengineering had never been deployed.

Long adaptation

The researchers then tried to calculate how plants and animals, all of which have adapted over the millennia to particular levels of rainfall and temperature, would respond. In many cases, the rate of warming would be four to seven times faster than the rate at which arthropods, birds, fish, mammals and reptiles could respond.

Climate change is already a threat to global biodiversity. Accelerated climate change after a period of containment would be even more dramatic.

“In many cases, you’d have to go one direction to find the same temperature but in a different direction to find the same precipitation. Plants, of course, can’t move reasonably at all. Some animals can move and some can’t,” said Professor Robock.

“We really need to look in a lot more detail at the impact on specific organisms and how they might adapt if geoengineering stops suddenly.” – Climate News Network

Using atmospheric aerosols to cut global warming is agreed to be risky. It might be even riskier to start it and then stop.

LONDON, 31 January, 2018 – Geoengineering, spraying atmospheric aerosols as the technofix answer to a warming planet, has been repeatedly denounced as dangerous by many critics. Now scientists say it could hide another hazard: once started, it might be dangerous to stop.

That is because their research shows that if this planetary sunscreen worked, and the technology was then brought to a halt, global warming would resume, at up to 10 times the speed.

And that would present even more danger for plants and animals already at risk from climate change, according to US scientists who write in the journal Nature Ecology and Evolution.

“Rapid warming after stopping would be a huge threat to the natural environment and biodiversity,” said Alan Robock, a climate scientist at Rutgers University – New Brunswick.

Huge risk

“If geoengineering ever stopped abruptly, it would be devastating, so you would have to be sure that it could be stopped gradually, and it is easy to think of scenarios that would prevent that.

“Imagine large droughts or floods around the world that could be blamed on geoengineering, and demands that it stop. Can we ever risk that?”

Almost all climate scientists argue that the proper way to control climate change is to drastically cut fossil fuel use and switch to wind, solar and water power to drive modern economies.

Even proponents of the technofix – the use of expensive technologies to screen or reflect sunlight by, for instance, spraying sulphate aerosols into the stratosphere – concede that prevention is best.

“If geoengineering ever stopped abruptly, it would be devastating, so you would have to be sure that it could be stopped gradually”

The geoengineering argument remains on the table of possibilities because, for the moment, progress towards real reduction is slow, and researchers have repeatedly warned that hopes of containing global warming, and limiting climate change, are dwindling.

So, once again, Rutgers scientists looked at ways of darkening the upper skies, and their implications. Although researchers have warned again and again of the dangers of such steps, at least one study has conceded that, in theory, the technology could be made to work.

So Professor Robock and colleagues considered the sky-spray solution again. They modelled the injection by high-flying aircraft of five million tons of sulphur dioxide into the upper atmosphere, over the equator, from 2020 to 2070. This is the annual equivalent of about one quarter of the sulphate aerosols hurled into the upper atmosphere by the eruption of Mt Pinatubo, in 1991, in the Philippines.

The sulphate clouds would spread evenly over the northern and southern hemispheres, to lower global temperatures by about 1°C, and bring them back down to the global average before the Industrial Revolution. But any halt in the programme would bring global warming back much faster than if geoengineering had never been deployed.

Long adaptation

The researchers then tried to calculate how plants and animals, all of which have adapted over the millennia to particular levels of rainfall and temperature, would respond. In many cases, the rate of warming would be four to seven times faster than the rate at which arthropods, birds, fish, mammals and reptiles could respond.

Climate change is already a threat to global biodiversity. Accelerated climate change after a period of containment would be even more dramatic.

“In many cases, you’d have to go one direction to find the same temperature but in a different direction to find the same precipitation. Plants, of course, can’t move reasonably at all. Some animals can move and some can’t,” said Professor Robock.

“We really need to look in a lot more detail at the impact on specific organisms and how they might adapt if geoengineering stops suddenly.” – Climate News Network

More harm than good with climate geo-engineering

Geo-engineering might be possible – but so far it doesn’t look practical. Yet another study sees dangers in the technofix.

LONDON, 24 November, 2017 – Geo-engineering – the untested technofix that would permit the continued use of fossil fuels – could create more problems than it could solve.

By masking sunlight with injections of sulphate aerosols in the stratosphere, nations could perhaps suppress some of the devastating hurricanes and typhoons that in a rapidly warming world threaten northern hemisphere cities. But they could also scorch the Sahel region of Africa, to threaten millions of lives and livelihoods, according to new research.

Geo-engineering is sometimes played as humanity’s have-your-cake-and-eat-it option: humans have already unthinkingly engineered climate change over the last 200 years by profligate combustion of coal, oil and gas that releases ever-growing concentrations of the greenhouse gas carbon dioxide into the atmosphere.

Since ferocious volcanic eruptions have been known to cool the global climate by pumping soot and sulphur dioxide into the upper atmosphere, some reason that scientists and technologists could play the same card, in a calculated fashion.

“This is not a technique that is ready to use in the near future: reducing CO2 emissions and planning our adaptation must remain top priorities for climate policy”

But shortly after one research team showed that, in theory at least, geo-engineering could be made to work, a second group has demonstrated that there would be a huge price to pay. And they call on policymakers to think carefully before testing any unilateral action.

“Our results confirm that regional solar geo-engineering is a highly risky strategy which could simultaneously benefit one region to the detriment of another,” said Anthony Jones, a climate scientist at the University of Exeter, UK, who led the study. 

“It is vital that policymakers take solar geo-engineering seriously and act swiftly to install effective regulation.”

This is an argument that has continued for more than a decade: in 2006, the Nobel laureate and chemist Paul Crutzen pointed out that, while burning hydrocarbon fuels, humans also released sulphate aerosols that represented a health hazard, linked to half a million deaths a year.

Multiple effects

If a proportion of this pollution reached the upper atmosphere, it would not only save lives, it would change the reflectivity of the planet, dim solar radiation, and contain global warming.

Since then, researchers the world over have repeatedly looked at the geo-engineering option, and repeatedly conceded that the ideal answer would be to stop burning fossil fuels.

And since greenhouse gas emissions have failed to fall, other groups have repeatedly returned to the study, to find that such solutions may not work, or that they could create more problems than they solve.

Dr Jones and his colleagues report in the journal Nature Communications that they tested the sulphate solution in simulation to find what others have suggested: that in addition to damping global temperature rise, a deliberate darkening of the skies would also suppress hurricane activity in the north Atlantic.

Drought risk

But, as others have argued, it would also heighten the likelihood of sustained drought in the Sahel, a region which extends across 14 nations in Africa, from Senegal to Ethiopia.

“It is obvious from first principles that stratospheric aerosol geo-engineering deployed in only one hemisphere would lead to huge shifts in tropical climate patterns,” said Peter Irvine, a researcher at Harvard University in the US, commenting on the study.

“Deploying stratospheric aerosol geo-engineering in only one hemisphere is pretty certainly a bad idea, and this work helps reinforce that view.”

And John Shepherd, an earth system scientist at the University of Southampton in the UK, said: “This is not a technique that is ready to use in the near future: reducing CO2 emissions and planning our adaptation must remain top priorities for climate policy.” – Climate News Network

Geo-engineering might be possible – but so far it doesn’t look practical. Yet another study sees dangers in the technofix.

LONDON, 24 November, 2017 – Geo-engineering – the untested technofix that would permit the continued use of fossil fuels – could create more problems than it could solve.

By masking sunlight with injections of sulphate aerosols in the stratosphere, nations could perhaps suppress some of the devastating hurricanes and typhoons that in a rapidly warming world threaten northern hemisphere cities. But they could also scorch the Sahel region of Africa, to threaten millions of lives and livelihoods, according to new research.

Geo-engineering is sometimes played as humanity’s have-your-cake-and-eat-it option: humans have already unthinkingly engineered climate change over the last 200 years by profligate combustion of coal, oil and gas that releases ever-growing concentrations of the greenhouse gas carbon dioxide into the atmosphere.

Since ferocious volcanic eruptions have been known to cool the global climate by pumping soot and sulphur dioxide into the upper atmosphere, some reason that scientists and technologists could play the same card, in a calculated fashion.

“This is not a technique that is ready to use in the near future: reducing CO2 emissions and planning our adaptation must remain top priorities for climate policy”

But shortly after one research team showed that, in theory at least, geo-engineering could be made to work, a second group has demonstrated that there would be a huge price to pay. And they call on policymakers to think carefully before testing any unilateral action.

“Our results confirm that regional solar geo-engineering is a highly risky strategy which could simultaneously benefit one region to the detriment of another,” said Anthony Jones, a climate scientist at the University of Exeter, UK, who led the study. 

“It is vital that policymakers take solar geo-engineering seriously and act swiftly to install effective regulation.”

This is an argument that has continued for more than a decade: in 2006, the Nobel laureate and chemist Paul Crutzen pointed out that, while burning hydrocarbon fuels, humans also released sulphate aerosols that represented a health hazard, linked to half a million deaths a year.

Multiple effects

If a proportion of this pollution reached the upper atmosphere, it would not only save lives, it would change the reflectivity of the planet, dim solar radiation, and contain global warming.

Since then, researchers the world over have repeatedly looked at the geo-engineering option, and repeatedly conceded that the ideal answer would be to stop burning fossil fuels.

And since greenhouse gas emissions have failed to fall, other groups have repeatedly returned to the study, to find that such solutions may not work, or that they could create more problems than they solve.

Dr Jones and his colleagues report in the journal Nature Communications that they tested the sulphate solution in simulation to find what others have suggested: that in addition to damping global temperature rise, a deliberate darkening of the skies would also suppress hurricane activity in the north Atlantic.

Drought risk

But, as others have argued, it would also heighten the likelihood of sustained drought in the Sahel, a region which extends across 14 nations in Africa, from Senegal to Ethiopia.

“It is obvious from first principles that stratospheric aerosol geo-engineering deployed in only one hemisphere would lead to huge shifts in tropical climate patterns,” said Peter Irvine, a researcher at Harvard University in the US, commenting on the study.

“Deploying stratospheric aerosol geo-engineering in only one hemisphere is pretty certainly a bad idea, and this work helps reinforce that view.”

And John Shepherd, an earth system scientist at the University of Southampton in the UK, said: “This is not a technique that is ready to use in the near future: reducing CO2 emissions and planning our adaptation must remain top priorities for climate policy.” – Climate News Network

Geo-engineering can work – if the world wants it

Geo-engineering can stop the Earth warming, at least in theory, scientists say, but doubts persist over the possible risks.

LONDON, 10 November, 2017 – Climate scientists now know that geo-engineering – in principle at least – would halt global warming and keep the world at the temperatures it will reach by 2020.

It is simple: inject millions of tons of sulphate aerosols into the stratosphere at carefully chosen locations, and keep on doing so for as long as humans continue to burn fossil fuels and release greenhouse gases into the atmosphere.

The desired effect: global temperatures will be contained because the pollutants in the upper atmosphere will dim the sun’s light and counteract the greenhouse effect of all the carbon dioxide pumped from power stations, vehicle exhausts, factory chimneys and burning forests.

It won’t be the perfect answer. The oceans will go on becoming more acidic, and the skies will become subtly darker. Rainfall patterns could be affected. Repairs to the ozone layer – an invisible shield against dangerous ultraviolet radiation – would be slowed.

“For decision makers to accurately weigh the pros and cons of geo-engineering against those of human-caused climate change, they need more information. Our goal is to better understand what geo-engineering can do and what it cannot”

The volumes of sulphate aerosols that would need to be flown to stratospheric heights and released each year would continue to grow as humans went on burning ever more fossil fuels.

The technical and energy demands of such an operation would be colossal. There could be serious geopolitical problems about the impacts and responsibility for such decisions. But, at least in principle, researchers now believe geo-engineering could be made to work.

“For decision makers to accurately weigh the pros and cons of geo-engineering against those of human-caused climate change, they need more information,” said Ben Kravitz, of the Pacific Northwest National Laboratory, and one of a consortium which has published a succession of five studies in the Journal of Geophysical Research – Atmospheres. “Our goal is to better understand what geo-engineering can do and what it cannot.”

Unkept promises

Climate scientists have repeatedly investigated the so-called techno-fix. By burning maybe 50 million years of fossil fuel deposits in just two centuries, humans have raised global temperatures and inadvertently engineered climate change.

So perhaps science and technology could come to the rescue, and deliberately engineer the climate to a new kind of stability. The consensus is that the ideal solution would be to stop burning fossil fuels and to start restoring the planet’s forests, the great absorbers of atmospheric carbon. But despite promises by the world’s nations in Paris in 2015, global temperatures continue to rise.

Geo-engineering is an idea that won’t go away. Research teams have repeatedly examined ideas for countering global warming, instead of reducing the cause, and found them wanting: such action world ultimately fail, or it would make the world’s problems worse, or at best it would take the heat out of the hurricane season.

But scientists from the US National Centre for Atmospheric Research, along with other US institutions and international colleagues, chose a different approach: what could geo-engineering achieve?

Natural model

Famously, an eruption of Mt Pinatubo in the Philippines in 1991 cooled the planet by dumping 20 million tons of sulphur dioxide in the stratosphere. The researchers used computer simulations to test the effect of what might be called artificial eruptions: how would stratospheric winds spread these sulphate aerosols, and how would this diffuse global dust cloud cool the planet, and for how long, and to what extent?

They played with the idea of injecting sulphates at 14 different sites at seven latitudes and two altitudes, to find that the idea worked best if injections happened at 30 degrees latitude, north and south. They experimented with varying levels of sulphur dioxide: up to 12 million metric tons at a time.

They found out how to contain overall global temperature rise to the predicted 2020 average: some regions however became – in their computer models – hotter or cooler than the citizens might appreciate.

But the challenge of keeping the world cool became more and more demanding. By the end of the century, if humans went on burning fossil fuels in the notorious business-as-usual scenario, their model demanded the equivalent of almost five Mt Pinatubo eruptions a year.  The research goes on.

Deployment delay

The Carnegie Climate Geoengineering Governance Initiative aims to encourage the development of governance for research on climate geo-engineering that is balanced between enabling and regulatory aspects.

One of its priorities is to put solar geo-engineering deployment on hold until the risks and potential benefits are better known and governance frameworks are agreed.

”We are still a long way from understanding all the interactions in the climate system that could be triggered by geo-engineering, which means we don’t yet understand the full range of possible side effects,” said scientist Simone Tilmes, of the National Centre for Atmospheric Research.

“But climate change also poses risks. Continuing research into geo-engineering is critical to assess benefits and side effects and to inform decision makers and society.” – Climate News Network

Geo-engineering can stop the Earth warming, at least in theory, scientists say, but doubts persist over the possible risks.

LONDON, 10 November, 2017 – Climate scientists now know that geo-engineering – in principle at least – would halt global warming and keep the world at the temperatures it will reach by 2020.

It is simple: inject millions of tons of sulphate aerosols into the stratosphere at carefully chosen locations, and keep on doing so for as long as humans continue to burn fossil fuels and release greenhouse gases into the atmosphere.

The desired effect: global temperatures will be contained because the pollutants in the upper atmosphere will dim the sun’s light and counteract the greenhouse effect of all the carbon dioxide pumped from power stations, vehicle exhausts, factory chimneys and burning forests.

It won’t be the perfect answer. The oceans will go on becoming more acidic, and the skies will become subtly darker. Rainfall patterns could be affected. Repairs to the ozone layer – an invisible shield against dangerous ultraviolet radiation – would be slowed.

“For decision makers to accurately weigh the pros and cons of geo-engineering against those of human-caused climate change, they need more information. Our goal is to better understand what geo-engineering can do and what it cannot”

The volumes of sulphate aerosols that would need to be flown to stratospheric heights and released each year would continue to grow as humans went on burning ever more fossil fuels.

The technical and energy demands of such an operation would be colossal. There could be serious geopolitical problems about the impacts and responsibility for such decisions. But, at least in principle, researchers now believe geo-engineering could be made to work.

“For decision makers to accurately weigh the pros and cons of geo-engineering against those of human-caused climate change, they need more information,” said Ben Kravitz, of the Pacific Northwest National Laboratory, and one of a consortium which has published a succession of five studies in the Journal of Geophysical Research – Atmospheres. “Our goal is to better understand what geo-engineering can do and what it cannot.”

Unkept promises

Climate scientists have repeatedly investigated the so-called techno-fix. By burning maybe 50 million years of fossil fuel deposits in just two centuries, humans have raised global temperatures and inadvertently engineered climate change.

So perhaps science and technology could come to the rescue, and deliberately engineer the climate to a new kind of stability. The consensus is that the ideal solution would be to stop burning fossil fuels and to start restoring the planet’s forests, the great absorbers of atmospheric carbon. But despite promises by the world’s nations in Paris in 2015, global temperatures continue to rise.

Geo-engineering is an idea that won’t go away. Research teams have repeatedly examined ideas for countering global warming, instead of reducing the cause, and found them wanting: such action world ultimately fail, or it would make the world’s problems worse, or at best it would take the heat out of the hurricane season.

But scientists from the US National Centre for Atmospheric Research, along with other US institutions and international colleagues, chose a different approach: what could geo-engineering achieve?

Natural model

Famously, an eruption of Mt Pinatubo in the Philippines in 1991 cooled the planet by dumping 20 million tons of sulphur dioxide in the stratosphere. The researchers used computer simulations to test the effect of what might be called artificial eruptions: how would stratospheric winds spread these sulphate aerosols, and how would this diffuse global dust cloud cool the planet, and for how long, and to what extent?

They played with the idea of injecting sulphates at 14 different sites at seven latitudes and two altitudes, to find that the idea worked best if injections happened at 30 degrees latitude, north and south. They experimented with varying levels of sulphur dioxide: up to 12 million metric tons at a time.

They found out how to contain overall global temperature rise to the predicted 2020 average: some regions however became – in their computer models – hotter or cooler than the citizens might appreciate.

But the challenge of keeping the world cool became more and more demanding. By the end of the century, if humans went on burning fossil fuels in the notorious business-as-usual scenario, their model demanded the equivalent of almost five Mt Pinatubo eruptions a year.  The research goes on.

Deployment delay

The Carnegie Climate Geoengineering Governance Initiative aims to encourage the development of governance for research on climate geo-engineering that is balanced between enabling and regulatory aspects.

One of its priorities is to put solar geo-engineering deployment on hold until the risks and potential benefits are better known and governance frameworks are agreed.

”We are still a long way from understanding all the interactions in the climate system that could be triggered by geo-engineering, which means we don’t yet understand the full range of possible side effects,” said scientist Simone Tilmes, of the National Centre for Atmospheric Research.

“But climate change also poses risks. Continuing research into geo-engineering is critical to assess benefits and side effects and to inform decision makers and society.” – Climate News Network

Geo-engineers propose climate compromise

Humans have unintentionally changed the world and turned up the temperature. A climate compromise might turn down the heat.

LONDON, 27 July, 2017 – Geo-engineering, the deliberate alteration of the planet to undo its inadvertent alteration by humans over the past 200 years, is back on the scientific agenda, with a climate compromise suggested as a possible solution.

One group wants to turn down the global thermostat and reverse the global warming trend set in train by greenhouse gases released by fossil fuel combustion, by thinning the almost invisible cirrus clouds that trap radiation and keep the planet warm.

Another group proposes to inject sulphur particles into the stratosphere, and keep on doing so for 160 years, to block enough sunlight and lower the planetary temperature.

And a third group wants to see a cocktail of both approaches: thin the high cirrus clouds that stop heat from escaping, and at the same pump particles into the stratosphere to scatter the incoming sunlight and limit the disadvantages of each approach by mixing them.

The verb “wants” in all three studies is neither fair nor appropriate: all three groups concede that the healthy answer is for humans to fulfil the pledge made in 2015, and start to reduce fossil fuel emissions so drastically that global average temperatures stay well below the 2°C maximum rise agreed by 197 nations at the Paris climate conference.

Change inevitable

But while most nations have yet to deliver on the plans they have made, and some nations have yet to even devise a plan, and one nation – the US – has announced its withdrawal from the agreement, scientists have been looking for ways to reverse the potentially catastrophic warming and climate change that is now inevitable if the world continues with its “business as usual scenario.”

And so, tentatively, and with unpromising conclusions, researchers have looked at ways to alter the planet to protect it from rising temperatures.

They have played with the idea of pumping sea water onto the Antarctic mainland ice
to increase the mass of ice and slow sea level rise.

They have looked at the northern icepack and wondered if making it whiter would increase solar reflection and slow global warming.

They have repeatedly investigated ways of reducing the incoming sunlight, usually by pumping sulphate aerosols into the atmosphere, and they have even investigated the possibility of making the ocean more thirsty for carbon dioxide, the most problematic greenhouse gas, by pumping iron into the sea to nourish the photosynthesising algae.

Bad answer

And other groups – and sometimes the same groups – have stressed the hazards: while darker skies might reduce hurricane ferocity, such approaches could drastically interfere with rainfall patterns, make life worse for some of the poorest people on Earth and anyway, in the long run, make things hotter.

All in all, the technofix has been pronounced a bad answer to a good question.

But by the end of the century, as sea levels rise by a metre and global average temperatures by 4°C or more, even a bad answer could be the only one on offer. So Ulrike Lohmann and Blaz Gasparini, two scientists from the Swiss Technical Institute known as ETH Zurich, write in the journal Science that the answer might lie in the clouds.

Cirrus clouds in particular don’t reflect much sunlight back into space, but because of the altitude and the temperature they do emit less long-wave radiation: they behave, in effect, rather like greenhouse gases.

So if cirrus clouds were carefully created by artificial means at lower altitudes, then perhaps they would trap less heat.

“More complicated geo-engineering solutions would likely do a bit better, but the best solution is simply to stop adding greenhouse gases to the atmosphere”

Such an experiment, the scientists concede, could go badly wrong, would not solve problems linked to rainfall patterns and might even make the world warmer. For the moment, they say: “cirrus cloud thinning should be viewed as a thought experiment.”

And in the same journal two scientists from the Max Planck Institute for Meteorology in Hamburg, Germany, and the US National Centre for Atmospheric Research in Boulder, Colorado, look once again at the stratosphere solution: what sulphur particles could do to cool the planet.

This is an idea already tested naturally. Volcanic eruptions have been linked to planetary cooling, and other groups have even warned that a modest nuclear war could darken the skies and lower global temperatures to potentially lethal levels.

So Ulrike Niemeier and her colleague Simone Tilmes consider what would be necessary if humans wait until 2040 to reduce fossil fuel use and look for effective ways to suck impossible volumes of carbon dioxide out of the atmosphere.

To limit the temperature increase to 2°C above pre-industrial levels, humans would have to pump sulphur into the stratosphere at a cost of $20bn a year for 160 years, to darken the skies and reduce incoming sunlight.

Side effects

Such a step, which could slow the water cycle and suppress the Asian monsoons, would not reduce the acidification of the oceans, and could trigger other unwelcome side effects that could lead to global conflicts. So, the scientists say, any such plan would need international agreement and supervision.

And, in the journal Geophysical Research Letters, Chinese, Indian and US researchers arrive at the compromise solution. The dark skies approach could reduce rain too much, thinner cirrus could reduce rain too little.

But computer models suggest that if both methods were deployed carefully and in concert, geo-engineers could cool the world but keep the rainfall steady overall.

“The same amount of rain fell around the globe in our models, but it fell in different places, which could create a big mismatch between what our economic infrastructure expects and what it will get,” said Ken Caldeira of the Carnegie Institution for Science in the US, and one of the authors.

“More complicated geo-engineering solutions would likely do a bit better, but the best solution is simply to stop adding greenhouse gases to the atmosphere.” – Climate News Network

Humans have unintentionally changed the world and turned up the temperature. A climate compromise might turn down the heat.

LONDON, 27 July, 2017 – Geo-engineering, the deliberate alteration of the planet to undo its inadvertent alteration by humans over the past 200 years, is back on the scientific agenda, with a climate compromise suggested as a possible solution.

One group wants to turn down the global thermostat and reverse the global warming trend set in train by greenhouse gases released by fossil fuel combustion, by thinning the almost invisible cirrus clouds that trap radiation and keep the planet warm.

Another group proposes to inject sulphur particles into the stratosphere, and keep on doing so for 160 years, to block enough sunlight and lower the planetary temperature.

And a third group wants to see a cocktail of both approaches: thin the high cirrus clouds that stop heat from escaping, and at the same pump particles into the stratosphere to scatter the incoming sunlight and limit the disadvantages of each approach by mixing them.

The verb “wants” in all three studies is neither fair nor appropriate: all three groups concede that the healthy answer is for humans to fulfil the pledge made in 2015, and start to reduce fossil fuel emissions so drastically that global average temperatures stay well below the 2°C maximum rise agreed by 197 nations at the Paris climate conference.

Change inevitable

But while most nations have yet to deliver on the plans they have made, and some nations have yet to even devise a plan, and one nation – the US – has announced its withdrawal from the agreement, scientists have been looking for ways to reverse the potentially catastrophic warming and climate change that is now inevitable if the world continues with its “business as usual scenario.”

And so, tentatively, and with unpromising conclusions, researchers have looked at ways to alter the planet to protect it from rising temperatures.

They have played with the idea of pumping sea water onto the Antarctic mainland ice
to increase the mass of ice and slow sea level rise.

They have looked at the northern icepack and wondered if making it whiter would increase solar reflection and slow global warming.

They have repeatedly investigated ways of reducing the incoming sunlight, usually by pumping sulphate aerosols into the atmosphere, and they have even investigated the possibility of making the ocean more thirsty for carbon dioxide, the most problematic greenhouse gas, by pumping iron into the sea to nourish the photosynthesising algae.

Bad answer

And other groups – and sometimes the same groups – have stressed the hazards: while darker skies might reduce hurricane ferocity, such approaches could drastically interfere with rainfall patterns, make life worse for some of the poorest people on Earth and anyway, in the long run, make things hotter.

All in all, the technofix has been pronounced a bad answer to a good question.

But by the end of the century, as sea levels rise by a metre and global average temperatures by 4°C or more, even a bad answer could be the only one on offer. So Ulrike Lohmann and Blaz Gasparini, two scientists from the Swiss Technical Institute known as ETH Zurich, write in the journal Science that the answer might lie in the clouds.

Cirrus clouds in particular don’t reflect much sunlight back into space, but because of the altitude and the temperature they do emit less long-wave radiation: they behave, in effect, rather like greenhouse gases.

So if cirrus clouds were carefully created by artificial means at lower altitudes, then perhaps they would trap less heat.

“More complicated geo-engineering solutions would likely do a bit better, but the best solution is simply to stop adding greenhouse gases to the atmosphere”

Such an experiment, the scientists concede, could go badly wrong, would not solve problems linked to rainfall patterns and might even make the world warmer. For the moment, they say: “cirrus cloud thinning should be viewed as a thought experiment.”

And in the same journal two scientists from the Max Planck Institute for Meteorology in Hamburg, Germany, and the US National Centre for Atmospheric Research in Boulder, Colorado, look once again at the stratosphere solution: what sulphur particles could do to cool the planet.

This is an idea already tested naturally. Volcanic eruptions have been linked to planetary cooling, and other groups have even warned that a modest nuclear war could darken the skies and lower global temperatures to potentially lethal levels.

So Ulrike Niemeier and her colleague Simone Tilmes consider what would be necessary if humans wait until 2040 to reduce fossil fuel use and look for effective ways to suck impossible volumes of carbon dioxide out of the atmosphere.

To limit the temperature increase to 2°C above pre-industrial levels, humans would have to pump sulphur into the stratosphere at a cost of $20bn a year for 160 years, to darken the skies and reduce incoming sunlight.

Side effects

Such a step, which could slow the water cycle and suppress the Asian monsoons, would not reduce the acidification of the oceans, and could trigger other unwelcome side effects that could lead to global conflicts. So, the scientists say, any such plan would need international agreement and supervision.

And, in the journal Geophysical Research Letters, Chinese, Indian and US researchers arrive at the compromise solution. The dark skies approach could reduce rain too much, thinner cirrus could reduce rain too little.

But computer models suggest that if both methods were deployed carefully and in concert, geo-engineers could cool the world but keep the rainfall steady overall.

“The same amount of rain fell around the globe in our models, but it fell in different places, which could create a big mismatch between what our economic infrastructure expects and what it will get,” said Ken Caldeira of the Carnegie Institution for Science in the US, and one of the authors.

“More complicated geo-engineering solutions would likely do a bit better, but the best solution is simply to stop adding greenhouse gases to the atmosphere.” – Climate News Network

World’s young face $535 trillion bill for climate

The next generation will have to pay a $535 trillion bill to tackle climate change, relying on unproven and speculative technology.

LONDON, 19 July, 2017 – One of the world’s most famous climate scientists has just calculated the financial burden that tomorrow’s young citizens will face to keep the globe at a habitable temperature and contain global warming and climate change – a $535 trillion bill.

And much of that will go on expensive technologies engineered to suck 1,000 billion metric tons of the greenhouse gas carbon dioxide from the air by the year 2100.

Of course, if humans started to reduce greenhouse gas emissions by 6% a year right now, the end of the century challenge would be to take 150 billion tonnes from the atmosphere, and most of this could be achieved simply by better forest and agricultural management, according to a new study in the journal Earth System Dynamics.

The study, authored by researchers from the US, France, China, the United Kingdom and Australia, rests on two arguments.

Slow start

One is that although the world’s nations vowed in Paris in 2015 to contain global warming by 2100 to “well below” 2°C relative to the average global temperatures for most of the planet’s history since the last Ice Age, concerted international action has been slow to start. One nation – the US – has already announced that it will withdraw from the Paris Agreement.

The other argument is that, even if humans do in the decades to come rise to the challenge, it could be too late: by then greenhouse gas concentrations could have reached a level in the atmosphere that would in the long run condemn the world to sea level rises of several metres, and a succession of economic and humanitarian disasters.

“Continued high fossil fuel emissions would saddle young people with a massive, expensive cleanup problem and growing deleterious climate impacts, which should provide incentive and obligation for governments to alter energy policies without further delay,” says James Hansen, of the Columbia University Earth Institute in the US, who led the study.

Professor Hansen, as director of the US space agency Nasa’s Institute for Space Studies, made global headlines in 1988, during a severe drought and heatwave on the North American continent, when he told a Washington senate committee: “It’s time to stop waffling so much and say the evidence is pretty strong that the greenhouse effect is here.”

Legal testimony

With that one sentence, he made climate science an enduring item on the political agenda. But the latest study is also part of a legal argument. It is in effect testimony in a lawsuit called Juliana et al vs the United States.

This case began under the last US administration. However, the US president, Donald Trump, who has dismissed the evidence of climate change as a “hoax”, has now been named in the case.

Professor Hansen has argued that even the ambitions of the historic Paris Accord will not be enough to avert disaster and displacement for millions. The benchmark for geologically recent warming levels was set 115,000 years ago, during a period between two Ice Ages, known to geologists as the Eemian

“We show that a target of limiting global warming to no more than +2°C relative to pre-industrial levels is not sufficient, as +2°C would be warmer than the Eemian period, when sea level reached plus 6-9 metres relative to today,” Professor Hansen said.

Lower CO2

At the heart of such arguments are calculations about imponderables that climatologists like to call the carbon budget and climate sensitivityThe first of these concerns the terrestrial and oceanic processes that release greenhouse gases into the atmosphere and then absorb them, and the second is a calculation about what a change in carbon dioxide levels really means for average global temperatures.

For most of human history, CO2 levels were around 280 parts per million. In the last two years they have reached 400 ppm, as a response to two centuries of fossil fuel combustion, and average global temperatures have risen by almost 1°C, with a record reading in 2016 of 1.3°C.

Professor Hansen and his colleagues want to see these atmospheric CO2 levels lowered to 350 ppm, to bring global temperature rise down to no more than a rise of 1°C later this century.

If the world’s nations can co-operate to do that, then most of the hard work to remove the carbon dioxide surplus from the air could be left to the world’s great forests.

“It is apparent that governments are leaving this problem on the shoulders of young people. This will not be easy or inexpensive” 

However, if carbon emissions go on growing at 2% a year (and during this century, they have grown faster), then those who are children now would have to commit to a costly technological answer based on the belief that carbon dioxide can be captured, compressed and stored deep underground.

Nobody knows how to do this on any significant scale. And if it could be done, it would be expensive: an estimated €500 trillion, or US$535 trillion.

“It is apparent that governments are leaving this problem on the shoulders of young people. This will not be easy or inexpensive,” says Hansen.

“We wanted to quantify the burden that is being left for young people, to support not only the legal case against the US government, but also many other cases that can be brought against other governments.” – Climate News Network

The next generation will have to pay a $535 trillion bill to tackle climate change, relying on unproven and speculative technology.

LONDON, 19 July, 2017 – One of the world’s most famous climate scientists has just calculated the financial burden that tomorrow’s young citizens will face to keep the globe at a habitable temperature and contain global warming and climate change – a $535 trillion bill.

And much of that will go on expensive technologies engineered to suck 1,000 billion metric tons of the greenhouse gas carbon dioxide from the air by the year 2100.

Of course, if humans started to reduce greenhouse gas emissions by 6% a year right now, the end of the century challenge would be to take 150 billion tonnes from the atmosphere, and most of this could be achieved simply by better forest and agricultural management, according to a new study in the journal Earth System Dynamics.

The study, authored by researchers from the US, France, China, the United Kingdom and Australia, rests on two arguments.

Slow start

One is that although the world’s nations vowed in Paris in 2015 to contain global warming by 2100 to “well below” 2°C relative to the average global temperatures for most of the planet’s history since the last Ice Age, concerted international action has been slow to start. One nation – the US – has already announced that it will withdraw from the Paris Agreement.

The other argument is that, even if humans do in the decades to come rise to the challenge, it could be too late: by then greenhouse gas concentrations could have reached a level in the atmosphere that would in the long run condemn the world to sea level rises of several metres, and a succession of economic and humanitarian disasters.

“Continued high fossil fuel emissions would saddle young people with a massive, expensive cleanup problem and growing deleterious climate impacts, which should provide incentive and obligation for governments to alter energy policies without further delay,” says James Hansen, of the Columbia University Earth Institute in the US, who led the study.

Professor Hansen, as director of the US space agency Nasa’s Institute for Space Studies, made global headlines in 1988, during a severe drought and heatwave on the North American continent, when he told a Washington senate committee: “It’s time to stop waffling so much and say the evidence is pretty strong that the greenhouse effect is here.”

Legal testimony

With that one sentence, he made climate science an enduring item on the political agenda. But the latest study is also part of a legal argument. It is in effect testimony in a lawsuit called Juliana et al vs the United States.

This case began under the last US administration. However, the US president, Donald Trump, who has dismissed the evidence of climate change as a “hoax”, has now been named in the case.

Professor Hansen has argued that even the ambitions of the historic Paris Accord will not be enough to avert disaster and displacement for millions. The benchmark for geologically recent warming levels was set 115,000 years ago, during a period between two Ice Ages, known to geologists as the Eemian

“We show that a target of limiting global warming to no more than +2°C relative to pre-industrial levels is not sufficient, as +2°C would be warmer than the Eemian period, when sea level reached plus 6-9 metres relative to today,” Professor Hansen said.

Lower CO2

At the heart of such arguments are calculations about imponderables that climatologists like to call the carbon budget and climate sensitivityThe first of these concerns the terrestrial and oceanic processes that release greenhouse gases into the atmosphere and then absorb them, and the second is a calculation about what a change in carbon dioxide levels really means for average global temperatures.

For most of human history, CO2 levels were around 280 parts per million. In the last two years they have reached 400 ppm, as a response to two centuries of fossil fuel combustion, and average global temperatures have risen by almost 1°C, with a record reading in 2016 of 1.3°C.

Professor Hansen and his colleagues want to see these atmospheric CO2 levels lowered to 350 ppm, to bring global temperature rise down to no more than a rise of 1°C later this century.

If the world’s nations can co-operate to do that, then most of the hard work to remove the carbon dioxide surplus from the air could be left to the world’s great forests.

“It is apparent that governments are leaving this problem on the shoulders of young people. This will not be easy or inexpensive” 

However, if carbon emissions go on growing at 2% a year (and during this century, they have grown faster), then those who are children now would have to commit to a costly technological answer based on the belief that carbon dioxide can be captured, compressed and stored deep underground.

Nobody knows how to do this on any significant scale. And if it could be done, it would be expensive: an estimated €500 trillion, or US$535 trillion.

“It is apparent that governments are leaving this problem on the shoulders of young people. This will not be easy or inexpensive,” says Hansen.

“We wanted to quantify the burden that is being left for young people, to support not only the legal case against the US government, but also many other cases that can be brought against other governments.” – Climate News Network

Natural gas can’t help to curb climate change

Too much reliance on natural gas to generate electricity means the Paris climate target will be missed and money wasted on underused pipelines.

LONDON, 22 June, 2017 – Natural gas will have to be phased out along with coal if the world is to be kept safe from dangerous climate change. And that seems likely to have to happen far sooner than most official forecasts, according to a new report.

If countries want to reach their Paris Agreement goals of limiting the long-term world temperature rise to 1.5°C, then many of the proposals to increase gas production and distribution will be unnecessary. New terminals and pipelines will never be fully used and will become stranded assets.

The authors also warn that unless countries realise quickly that further investment in gas production is both unnecessary and damaging to the climate, they may lock themselves into emissions that they cannot afford to make.

The report, Foot off the Gas, is published by the Climate Action Tracker (CAT), an independent science-based assessment which tracks countries’ emission commitments and actions.

CAT’s members are Climate Analytics, Ecofys and NewClimate Institute, with the Potsdam Institute for Climate Impact Research as a collaborator.

Double overestimate

The report says part of the problem is that governments guided by projections from the International Energy Agency (IEA) are overestimating the need for natural gas, both to replace coal and to act as emergency back-up when supplies from intermittent renewables falter.

IEA annual reports have consistently underestimated the speed of growth of renewables, but have also failed to grasp the increasing role of other technologies like bio-gas, battery storage and hydrogen to even out any intermittency in supplies of electricity from solar and wind, it says.

“One example is China, where in 2016 the IEA projected renewables would rise to 7.2% of the power supply by 2020 – but by the end of 2016 they had already reached 8%. Additionally, India and the Middle East are also seeing renewables rising much faster than mainstream projections,” said Niklas Höhne from NewClimate Institute

Changes in the way grids are organised are already happening in Europe, together with the building of long-distance connectors between countries that exchange renewable energy  when one has a surplus. These developments cut the need for generation from gas.

Two-way exchange

The best-known example is hydro-electricity from Norway being used to boost wind energy supply in Denmark, and the reverse happening when there is a surplus of wind energy in Denmark and Germany.

Already many of the very expensive pipelines for transporting gas are under-utilised, and expensive ports and facilities to export liquid petroleum gas will never be used at full capacity, the report claims.

For example, utilisation rates of US natural gas infrastructure are at 54%, and are even lower in Europe, at 25%. 

“This over-investment in natural gas infrastructure is likely to lead to either emissions overshooting the Paris Agreement’s 1.5°C and 2°C goals – or a large number of stranded assets as the shift to cheaper renewables takes place, “ said Andrzej Ancygier of Climate Analytics.

“Natural gas is often perceived as a ‘clean’ source of energy that complements variable renewable technologies … gas is not as ‘clean’ as often thought”

The report sees a dwindling role for natural gas towards the middle of the century because of increasing competition from renewables that continue to get cheaper.

This is contrary to the official line that gas consumption will continue to rise and is an important “bridging fuel” towards a carbon-free world.

“Natural gas is often perceived as a ‘clean’ source of energy that complements variable renewable technologies. However, there are persistent issues with fugitive emissions during gas extraction and transport that show that gas is not as ‘clean’ as often thought,” said Bill Hare of Climate Analytics

“Natural gas will disappear from the power sector in a Paris Agreement-compatible world, where emissions need to be around zero by mid-century.” 

Doubt is also cast on the possibility that gas can be used along with carbon capture and storage. Although the report says that some gains can be made, it is an expensive technology  – and even more costly if it is going to be a reliable way of reducing emissions to near 100%. Currently too many greenhouse gases still escape into the atmosphere at various stages of the process. – Climate News Network

Too much reliance on natural gas to generate electricity means the Paris climate target will be missed and money wasted on underused pipelines.

LONDON, 22 June, 2017 – Natural gas will have to be phased out along with coal if the world is to be kept safe from dangerous climate change. And that seems likely to have to happen far sooner than most official forecasts, according to a new report.

If countries want to reach their Paris Agreement goals of limiting the long-term world temperature rise to 1.5°C, then many of the proposals to increase gas production and distribution will be unnecessary. New terminals and pipelines will never be fully used and will become stranded assets.

The authors also warn that unless countries realise quickly that further investment in gas production is both unnecessary and damaging to the climate, they may lock themselves into emissions that they cannot afford to make.

The report, Foot off the Gas, is published by the Climate Action Tracker (CAT), an independent science-based assessment which tracks countries’ emission commitments and actions.

CAT’s members are Climate Analytics, Ecofys and NewClimate Institute, with the Potsdam Institute for Climate Impact Research as a collaborator.

Double overestimate

The report says part of the problem is that governments guided by projections from the International Energy Agency (IEA) are overestimating the need for natural gas, both to replace coal and to act as emergency back-up when supplies from intermittent renewables falter.

IEA annual reports have consistently underestimated the speed of growth of renewables, but have also failed to grasp the increasing role of other technologies like bio-gas, battery storage and hydrogen to even out any intermittency in supplies of electricity from solar and wind, it says.

“One example is China, where in 2016 the IEA projected renewables would rise to 7.2% of the power supply by 2020 – but by the end of 2016 they had already reached 8%. Additionally, India and the Middle East are also seeing renewables rising much faster than mainstream projections,” said Niklas Höhne from NewClimate Institute

Changes in the way grids are organised are already happening in Europe, together with the building of long-distance connectors between countries that exchange renewable energy  when one has a surplus. These developments cut the need for generation from gas.

Two-way exchange

The best-known example is hydro-electricity from Norway being used to boost wind energy supply in Denmark, and the reverse happening when there is a surplus of wind energy in Denmark and Germany.

Already many of the very expensive pipelines for transporting gas are under-utilised, and expensive ports and facilities to export liquid petroleum gas will never be used at full capacity, the report claims.

For example, utilisation rates of US natural gas infrastructure are at 54%, and are even lower in Europe, at 25%. 

“This over-investment in natural gas infrastructure is likely to lead to either emissions overshooting the Paris Agreement’s 1.5°C and 2°C goals – or a large number of stranded assets as the shift to cheaper renewables takes place, “ said Andrzej Ancygier of Climate Analytics.

“Natural gas is often perceived as a ‘clean’ source of energy that complements variable renewable technologies … gas is not as ‘clean’ as often thought”

The report sees a dwindling role for natural gas towards the middle of the century because of increasing competition from renewables that continue to get cheaper.

This is contrary to the official line that gas consumption will continue to rise and is an important “bridging fuel” towards a carbon-free world.

“Natural gas is often perceived as a ‘clean’ source of energy that complements variable renewable technologies. However, there are persistent issues with fugitive emissions during gas extraction and transport that show that gas is not as ‘clean’ as often thought,” said Bill Hare of Climate Analytics

“Natural gas will disappear from the power sector in a Paris Agreement-compatible world, where emissions need to be around zero by mid-century.” 

Doubt is also cast on the possibility that gas can be used along with carbon capture and storage. Although the report says that some gains can be made, it is an expensive technology  – and even more costly if it is going to be a reliable way of reducing emissions to near 100%. Currently too many greenhouse gases still escape into the atmosphere at various stages of the process. – Climate News Network

Geo-engineering unlikely to ease climate fears

Attempts to limit climate change by using the novel technologies known as geo-engineering are very unlikely to work, leading biologists say.

LONDON, 1 November, 2016 – The global watchdog responsible for protecting the worlds wealth of species, the UNs  Convention on Biological Diversity (CBD), has looked at the hopes for reining in climate change through geo-engineering. Its bleak conclusion, echoing that reached by many independent scientists, is that the chances are “highly uncertain”.

“Novel means”, in this context, describes trying to reduce greenhouse gas (GHG) emissions by removing them from the atmosphere, and altering the amount of heat from the Sun that reaches the Earth.  

Some scientists and policymakers say geo-engineering, as these strategies are collectively known, is essential if the world is to meet the goals of the Paris Agreement. This is because current attempts to reduce emissions cannot make big enough cuts fast enough to keep global average temperatures from rising more than 2°C above their pre-industrial levels, the Agreement’s basic goal.

But the CBD says in a report that geo-engineering, while it could possibly help to prevent the world overheating, might endanger global biodiversity and have other unpredictable effects.

Many independent analysts have raised similar concerns.Attempts to increase the amount of carbon in the oceans, in order to remove GHGs, have so far shown disappointing results. One report doubted that geo-engineering could slow sea-level rise. Another said it could not arrest the melting of Arctic ice. A third study found that geo-engineering would make things little better and might even make global warming worse.  

Transboundary impacts

The lead author of the CBD geo-engineering report is a British scientist, Dr Phillip Williamson, of the UK’s Natural Environment Research Council. He is an associate fellow in the School of Environmental Sciences at the University of East Anglia, UK.

The CBD originally became involved in climate geo-engineering in 2008, because member governments were concerned that experiments to fertilise the oceans could pose unknown risks to the environment (they were then unregulated when carried out in international waters).

The CBD’s concern expanded to include other geo-engineering techniques, especially atmospheric methods which could have uncertain transboundary impacts. Some scientists argue that “geo-engineering” is a hazily-defined term and prefer to speak instead simply of “greenhouse gas removal”.

Dr Williamson and his colleagues say assessment of the impacts of geo-engineering on biodiversity “is not straightforward and is subject to many uncertainties”.

On greenhouse gas removal they warn that removing a given quantity of a greenhouse gas would not fully compensate for an earlier ‘overshoot’ of emissions.

New risks

In some cases, they say, the cure may be worse than the disease: “The large-scale deployment of bioenergy with carbon capture and storage (BECCS) seems likely to have significant negative impacts on biodiversity through land use change.”

When it comes to attempts to reflect sunlight back out into space or to manage solar radiation, a familiar theme recurs: “There are high levels of uncertainty about the impacts of SRM [solar radiation management] techniques, which could present significant new risks to biodiversity.”

Time and again, it seems, a potential advance is liable to be cancelled by an equally likely reverse: if SRM benefits coral reefs by decreasing temperature-induced bleaching (as it may), in certain conditions “it may also increase, indirectly, the impacts of ocean acidification.” There could even be a risk in some circumstances of loss to the Earth’s protective ozone layer.

Dr Williamson and his colleagues believe that geo-engineering is essential – if it can be made to work – because of the diminishing chances that anything else will.

“I’m sceptical. That’s not to say bio-energy with carbon capture and storage is impossible, but it seems extremely unlikely to be feasible”

They write: “It may still be possible that deep and very rapid decarbonisation by all countries might allow climate change to be kept within a 2°C limit by emission reduction alone. However, any such window of opportunity is rapidly closing.”

Repeatedly, those two words recur: a suggested technique or development will be “highly uncertain”. Most of the report amounts to a very cautious call for more research, coupled with an implicit acceptance that in the end geo-engineering is unlikely to prove capable of contributing much to climate mitigation.

Dr Williamson told the Climate News Network: “I’m sceptical. That’s not to say bio-energy with carbon capture and storage is impossible, but it seems extremely unlikely to be feasible (for all sorts of reasons)” at the scale needed.

When the CBD member governments meet in December they are expected to call for more research: a safe option in most circumstances, but far from a ringing endorsement of a technology once seen as very promising. – Climate News Network

Attempts to limit climate change by using the novel technologies known as geo-engineering are very unlikely to work, leading biologists say.

LONDON, 1 November, 2016 – The global watchdog responsible for protecting the worlds wealth of species, the UNs  Convention on Biological Diversity (CBD), has looked at the hopes for reining in climate change through geo-engineering. Its bleak conclusion, echoing that reached by many independent scientists, is that the chances are “highly uncertain”.

“Novel means”, in this context, describes trying to reduce greenhouse gas (GHG) emissions by removing them from the atmosphere, and altering the amount of heat from the Sun that reaches the Earth.  

Some scientists and policymakers say geo-engineering, as these strategies are collectively known, is essential if the world is to meet the goals of the Paris Agreement. This is because current attempts to reduce emissions cannot make big enough cuts fast enough to keep global average temperatures from rising more than 2°C above their pre-industrial levels, the Agreement’s basic goal.

But the CBD says in a report that geo-engineering, while it could possibly help to prevent the world overheating, might endanger global biodiversity and have other unpredictable effects.

Many independent analysts have raised similar concerns.Attempts to increase the amount of carbon in the oceans, in order to remove GHGs, have so far shown disappointing results. One report doubted that geo-engineering could slow sea-level rise. Another said it could not arrest the melting of Arctic ice. A third study found that geo-engineering would make things little better and might even make global warming worse.  

Transboundary impacts

The lead author of the CBD geo-engineering report is a British scientist, Dr Phillip Williamson, of the UK’s Natural Environment Research Council. He is an associate fellow in the School of Environmental Sciences at the University of East Anglia, UK.

The CBD originally became involved in climate geo-engineering in 2008, because member governments were concerned that experiments to fertilise the oceans could pose unknown risks to the environment (they were then unregulated when carried out in international waters).

The CBD’s concern expanded to include other geo-engineering techniques, especially atmospheric methods which could have uncertain transboundary impacts. Some scientists argue that “geo-engineering” is a hazily-defined term and prefer to speak instead simply of “greenhouse gas removal”.

Dr Williamson and his colleagues say assessment of the impacts of geo-engineering on biodiversity “is not straightforward and is subject to many uncertainties”.

On greenhouse gas removal they warn that removing a given quantity of a greenhouse gas would not fully compensate for an earlier ‘overshoot’ of emissions.

New risks

In some cases, they say, the cure may be worse than the disease: “The large-scale deployment of bioenergy with carbon capture and storage (BECCS) seems likely to have significant negative impacts on biodiversity through land use change.”

When it comes to attempts to reflect sunlight back out into space or to manage solar radiation, a familiar theme recurs: “There are high levels of uncertainty about the impacts of SRM [solar radiation management] techniques, which could present significant new risks to biodiversity.”

Time and again, it seems, a potential advance is liable to be cancelled by an equally likely reverse: if SRM benefits coral reefs by decreasing temperature-induced bleaching (as it may), in certain conditions “it may also increase, indirectly, the impacts of ocean acidification.” There could even be a risk in some circumstances of loss to the Earth’s protective ozone layer.

Dr Williamson and his colleagues believe that geo-engineering is essential – if it can be made to work – because of the diminishing chances that anything else will.

“I’m sceptical. That’s not to say bio-energy with carbon capture and storage is impossible, but it seems extremely unlikely to be feasible”

They write: “It may still be possible that deep and very rapid decarbonisation by all countries might allow climate change to be kept within a 2°C limit by emission reduction alone. However, any such window of opportunity is rapidly closing.”

Repeatedly, those two words recur: a suggested technique or development will be “highly uncertain”. Most of the report amounts to a very cautious call for more research, coupled with an implicit acceptance that in the end geo-engineering is unlikely to prove capable of contributing much to climate mitigation.

Dr Williamson told the Climate News Network: “I’m sceptical. That’s not to say bio-energy with carbon capture and storage is impossible, but it seems extremely unlikely to be feasible (for all sorts of reasons)” at the scale needed.

When the CBD member governments meet in December they are expected to call for more research: a safe option in most circumstances, but far from a ringing endorsement of a technology once seen as very promising. – Climate News Network