Tag Archives: atmosphere

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2C rise will be a disaster say leading scientists

FOR IMMEDIATE RELEASE Countries round the world have pledged to try and limit the average global temperature rise to 2C above pre industrial figures. That’s way too high and would threaten major dislocations for civilization say a group of prominent scientists. London, 3 December – Governments have set the wrong target to limit climate change. The goal at present – to limit global warming to a maximum of 2°C higher than the average for most of human history  – “would have consequences that can be described as disastrous”, say 18 scientists in a review paper in the journal PLOS One. With a 2°C increase, “sea level rise of several meters could be expected,” they say.  “Increased climate extremes, already apparent at 0.8°C warming, would be more severe. Coral reefs and associated species, already stressed with current conditions, would be decimated by increased acidification, temperature and sea level rise.

Hansen at helm

The paper’s lead author is James Hansen, now at Columbia University, New York, and the former NASA scientist who in 1988 put global warming on the world’s front pages by telling a US government committee that “It’s time to stop waffling so much and say the evidence is pretty strong that the greenhouse effect is here.” Hansen’s fellow authors include the economist Jeffrey Sachs of Columbia University and the biologist Camille Parmesan, of the University of Plymouth in the UK and the University of Texas at Austin, USA. Their argument is that humanity and nature – “the modern world as we know it” – is adapted to what scientists call the Holocene climate that has existed for more than 10,000 years – since the end of the Ice Age, the beginnings of agriculture and the first settlement of the cities. Warming of 1°C relative to 1880–1920 keeps global temperature close to the Holocene range, but warming of 2°C, could cause “major dislocations for civilization.”

Clear arguments

The scientists study, uncompromisingly entitled “Assessing ‘dangerous climate change’: required reduction of carbon emissions to protect young people, future generations and nature” differs from many such climate analyses because it sets out its argument with remarkable directness and clarity, and serves as a useful briefing document for anyone – politicians, journalists and lay audiences – anxious to better understand the machinery of climate, and the forces that seem to be about to dictate climate change. Its critics will point out that it is also remarkably short on the usual circumlocutions, caveats, disclaimers and equivocations that tend to characterise most scientific papers. Hansen and his co-authors are however quite open about the major areas of uncertainty: their implicit argument is that if the worst outcomes turn out to be true, the consequences for humankind could be catastrophic.

Feedback is critical

The scientists case is that most political debate addresses the questions of reducing greenhouse gas emissions, but does not and perhaps cannot factor in the all potentially dangerous unknowns – the slow feedbacks that will follow the thawing of the Arctic, the release of frozen reserves of methane and carbon dioxide in the permafrost, and the melting of polar ice into the oceans. They point out that 170 nations have agreed on the need to limit fossil fuel emissions to avoid dangerous human-made climate change. “However the stark reality is that global emissions have accelerated, and new efforts are underway to massively expand fossil fuel extractions by drilling to increasing ocean depths and into the Arctic, squeezing oil from tar sands and tar shale, hydro-fracking to expand extraction of natural gas, developing exploitation of methane hydrates and mining of coal via mountain-top removal and mechanised long wall-mining.”

Still time

The scientists argue that swift and drastic action to limit global greenhouse gas emissions and contain warming to around 1°C would have two useful consequences. One is that it would not be far from the climate variations experienced as normal during the last 10,000 years, and secondly that it would make it more likely that the biosphere, and the soil, would be able to sequester a substantial proportion of the carbon dioxide released by human industrial civilisation. Trees are, in essence, captive carbon dioxide. But the warmer the world becomes, the more likely it is that existing forests – the Amazon, for example – will start to release more CO2 than they absorb, making the planet progressively even warmer. Therefore the scientists make a case for limiting overall global carbon emissions to 500 gigatonnes rather than the 1,000 billion tonnes in the 2°C rise scenario. “Although there is merit in simply chronicling what is happening, there is still opportunity for humanity to exercise free will,” says Hansen. – Climate News Network  

FOR IMMEDIATE RELEASE Countries round the world have pledged to try and limit the average global temperature rise to 2C above pre industrial figures. That’s way too high and would threaten major dislocations for civilization say a group of prominent scientists. London, 3 December – Governments have set the wrong target to limit climate change. The goal at present – to limit global warming to a maximum of 2°C higher than the average for most of human history  – “would have consequences that can be described as disastrous”, say 18 scientists in a review paper in the journal PLOS One. With a 2°C increase, “sea level rise of several meters could be expected,” they say.  “Increased climate extremes, already apparent at 0.8°C warming, would be more severe. Coral reefs and associated species, already stressed with current conditions, would be decimated by increased acidification, temperature and sea level rise.

Hansen at helm

The paper’s lead author is James Hansen, now at Columbia University, New York, and the former NASA scientist who in 1988 put global warming on the world’s front pages by telling a US government committee that “It’s time to stop waffling so much and say the evidence is pretty strong that the greenhouse effect is here.” Hansen’s fellow authors include the economist Jeffrey Sachs of Columbia University and the biologist Camille Parmesan, of the University of Plymouth in the UK and the University of Texas at Austin, USA. Their argument is that humanity and nature – “the modern world as we know it” – is adapted to what scientists call the Holocene climate that has existed for more than 10,000 years – since the end of the Ice Age, the beginnings of agriculture and the first settlement of the cities. Warming of 1°C relative to 1880–1920 keeps global temperature close to the Holocene range, but warming of 2°C, could cause “major dislocations for civilization.”

Clear arguments

The scientists study, uncompromisingly entitled “Assessing ‘dangerous climate change’: required reduction of carbon emissions to protect young people, future generations and nature” differs from many such climate analyses because it sets out its argument with remarkable directness and clarity, and serves as a useful briefing document for anyone – politicians, journalists and lay audiences – anxious to better understand the machinery of climate, and the forces that seem to be about to dictate climate change. Its critics will point out that it is also remarkably short on the usual circumlocutions, caveats, disclaimers and equivocations that tend to characterise most scientific papers. Hansen and his co-authors are however quite open about the major areas of uncertainty: their implicit argument is that if the worst outcomes turn out to be true, the consequences for humankind could be catastrophic.

Feedback is critical

The scientists case is that most political debate addresses the questions of reducing greenhouse gas emissions, but does not and perhaps cannot factor in the all potentially dangerous unknowns – the slow feedbacks that will follow the thawing of the Arctic, the release of frozen reserves of methane and carbon dioxide in the permafrost, and the melting of polar ice into the oceans. They point out that 170 nations have agreed on the need to limit fossil fuel emissions to avoid dangerous human-made climate change. “However the stark reality is that global emissions have accelerated, and new efforts are underway to massively expand fossil fuel extractions by drilling to increasing ocean depths and into the Arctic, squeezing oil from tar sands and tar shale, hydro-fracking to expand extraction of natural gas, developing exploitation of methane hydrates and mining of coal via mountain-top removal and mechanised long wall-mining.”

Still time

The scientists argue that swift and drastic action to limit global greenhouse gas emissions and contain warming to around 1°C would have two useful consequences. One is that it would not be far from the climate variations experienced as normal during the last 10,000 years, and secondly that it would make it more likely that the biosphere, and the soil, would be able to sequester a substantial proportion of the carbon dioxide released by human industrial civilisation. Trees are, in essence, captive carbon dioxide. But the warmer the world becomes, the more likely it is that existing forests – the Amazon, for example – will start to release more CO2 than they absorb, making the planet progressively even warmer. Therefore the scientists make a case for limiting overall global carbon emissions to 500 gigatonnes rather than the 1,000 billion tonnes in the 2°C rise scenario. “Although there is merit in simply chronicling what is happening, there is still opportunity for humanity to exercise free will,” says Hansen. – Climate News Network  

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Signs of forests adapting to growing CO2 levels

FOR IMMEDIATE RELEASE LONDON, 9 August – Trees may be getting more efficient in the way they manage water. They could be exploiting the higher levels of carbon dioxide in the atmosphere, growing foliage from a lower uptake of groundwater. If so, then the carbon dioxide fertilisation effect – predicted by theorists and observed in laboratory experiments – could be real. This is a provisional finding, because it is pretty difficult to measure the precise economy of a whole forest or an open wilderness. But Trevor Keenan  – of Macquarie University in Australia and at present at Harvard University in the US – and colleagues report in Nature that they used an indirect measure, called the eddy-covariance technique, to monitor the way managed forests handle two important gases: carbon dioxide and water vapour. Carbon dioxide levels in the atmosphere were once 280 parts per million; they are now 400 ppm and still rising. For more than 20 years, rigs have towered above the world’s forests recording eddy co-variance, measuring carbon uptake and water-use over areas of a square kilometre. Keenan and his fellow-researchers looked at the data from 21 temperate and boreal forests in the northern hemisphere and found a remarkably consistent trend: as the years rolled by, and carbon dioxide levels rose, forests used water more efficiently, and this was true for all 21 sites. This so-called fertilisation effect has been independently confirmed in arid zones, again by indirect research, through the work of an Australian team studying satellite data, and also seems consistent with a finding reported in Nature Climate Change that tropical forest trees are now producing more flowers, even though the observed temperature rises in the tropics have so far only been modest. The implication of the most recent research from the boreal and temperate forests is that plants could be partially closing their stomata to keep their carbon levels at a constant level. This finding, like much in science, raises as many questions as it answers. How plants “know” what to do in such circumstances, and how they do it, is still a mystery: Plants exploit atmospheric carbon dioxide so it should be no surprise that a better supply leads to more efficient growth. But more carbon dioxide also means higher temperatures, more evaporation, more precipitation and more cloud cover, so it has been difficult to observe the impact. Whether this will turn out in the long run to be a positive feedback that could, to some slight extent, slow global warming is uncertain. Plants are also sensitive to extreme heat and drought, two other unwelcome companions of climate change due to human emissions of greenhouse gases such as carbon dioxide, so it is too soon to suggest that forests will emerge as the winners. Other scientists still have to confirm the effect, and measure its scale more accurately. But the latest research does suggest trees are responding to change. “Our analysis suggests that rising atmospheric carbon dioxide is having a direct and unexpectedly strong influence on ecosystem processes and biosphere-atmosphere interactions in temperate and boreal forests,” says one of the authors, Dave Hollinger of the US Forest Service. – Climate News Network  

FOR IMMEDIATE RELEASE LONDON, 9 August – Trees may be getting more efficient in the way they manage water. They could be exploiting the higher levels of carbon dioxide in the atmosphere, growing foliage from a lower uptake of groundwater. If so, then the carbon dioxide fertilisation effect – predicted by theorists and observed in laboratory experiments – could be real. This is a provisional finding, because it is pretty difficult to measure the precise economy of a whole forest or an open wilderness. But Trevor Keenan  – of Macquarie University in Australia and at present at Harvard University in the US – and colleagues report in Nature that they used an indirect measure, called the eddy-covariance technique, to monitor the way managed forests handle two important gases: carbon dioxide and water vapour. Carbon dioxide levels in the atmosphere were once 280 parts per million; they are now 400 ppm and still rising. For more than 20 years, rigs have towered above the world’s forests recording eddy co-variance, measuring carbon uptake and water-use over areas of a square kilometre. Keenan and his fellow-researchers looked at the data from 21 temperate and boreal forests in the northern hemisphere and found a remarkably consistent trend: as the years rolled by, and carbon dioxide levels rose, forests used water more efficiently, and this was true for all 21 sites. This so-called fertilisation effect has been independently confirmed in arid zones, again by indirect research, through the work of an Australian team studying satellite data, and also seems consistent with a finding reported in Nature Climate Change that tropical forest trees are now producing more flowers, even though the observed temperature rises in the tropics have so far only been modest. The implication of the most recent research from the boreal and temperate forests is that plants could be partially closing their stomata to keep their carbon levels at a constant level. This finding, like much in science, raises as many questions as it answers. How plants “know” what to do in such circumstances, and how they do it, is still a mystery: Plants exploit atmospheric carbon dioxide so it should be no surprise that a better supply leads to more efficient growth. But more carbon dioxide also means higher temperatures, more evaporation, more precipitation and more cloud cover, so it has been difficult to observe the impact. Whether this will turn out in the long run to be a positive feedback that could, to some slight extent, slow global warming is uncertain. Plants are also sensitive to extreme heat and drought, two other unwelcome companions of climate change due to human emissions of greenhouse gases such as carbon dioxide, so it is too soon to suggest that forests will emerge as the winners. Other scientists still have to confirm the effect, and measure its scale more accurately. But the latest research does suggest trees are responding to change. “Our analysis suggests that rising atmospheric carbon dioxide is having a direct and unexpectedly strong influence on ecosystem processes and biosphere-atmosphere interactions in temperate and boreal forests,” says one of the authors, Dave Hollinger of the US Forest Service. – Climate News Network