Slowing tropical cyclones bring more mayhem

Tropical cyclones are slowing down. Hurricanes have lost their hurry. Paradoxically, this is bad news: they have more time to work their mischief.

LONDON, 15 June, 2018 – Tropical cyclones are moving more slowly. As temperatures rise, the pace at which a hurricane storms across a landscape has slowed perceptibly in the last 70 years. But the slowdown means each hurricane has more time to do more damage and deliver more flooding.

“Tropical cyclones over land have slowed down 20% in the Atlantic, 30% in the northwestern Pacific and 19% in the Australian region,” said James Kossin, of the US National Oceanic and Atmospheric Administration’s national centres for environmental information.

“These trends are almost certainly increasing local rainfall totals and freshwater flooding, which is associated with a very high mortality risk.”

He reports in the journal Nature that thanks to atmospheric warming as a consequence of the profligate combustion of fossil fuels in the last century, the summer tropical circulation has slowed and, along with it, hurricane and typhoon speeds. Overall, since 1940, cyclone movements have slowed by 10%; over some land areas, they have slowed much more.

But as the temperature goes up, the capacity of the atmosphere to hold moisture increases – by at least 7% with each degree Centigrade. That means a tropical cyclone – a whirling system of terrifying winds bearing huge quantities of water – has both more water, and more time to drop it over land.

Harvey’s warning

And Dr Kossin cites the example of Hurricane Harvey which in 2017 dumped more than 1.25 metres of water on Houston, Texas and the surrounding countryside in just five days. Devastating floods displaced 30,000 people, and 89 died. Economic losses were assessed at more than $126bn.

This shift in what researchers call the translation speed is new – and is only the latest study in a procession of alarming findings about the response of the winds in a warming world.

Researchers have already established that hurricanes are gaining in ferocity – that is, becoming more intense – at a faster rate than they did decades ago. They have warned that windstorms’ capacity to damage the world’s economy is on the increase directly because of global warming and consequent climate change, and they have identified a trend in hurricane geography: the storms are moving further north, in the northern hemisphere.

The combination of rising sea levels and fiercer storms could create, some argue, a new class of climate refugee in the US. And they have bad news for Texas: more storms like Harvey could be on the way.

“These trends are almost certainly increasing local rainfall totals and freshwater flooding, which is associated with a very high mortality risk”

In the course of the last century, global average temperatures have, as a consequence of the notorious greenhouse effect, gone up by around 1°C. Around 195 nations agreed in Paris in 2015 to attempt to contain global warming to 1.5°C in total by 2100, but gloomy forecasts suggest that unless action becomes urgent, temperatures will rise much higher.

And that means that hurricanes will go on slowing, to deliver ever more damage as they linger over coastal cities and farmlands.

“The observed 10% slowdown occurred in a period when the planet warmed by 0.5°C, but this does not provide a true measure of climate sensitivity, and more study is needed to determine how much more slowing will occur with continued warming,” Dr Kossin said.

“Still, it’s entirely plausible that local rainfall increases could actually be dominated by this slowdown rather than that the expected rain-rate increases due to global warming”. – Climate News Network

Homeless Bangladeshis flee before rising waters

Rising sea levels and recurrent floods mean more homeless Bangladeshis, with unpredictably changing rainfall patterns compounding their plight.

LONDON, 13 June, 2018 – As another monsoon season begins, huge numbers of homeless Bangladeshis are once again bracing themselves against the onslaught of floods and the sight of large chunks of land being devoured by rising water levels.

Bangladesh, on the Bay of Bengal, is low-lying and crisscrossed by a web of rivers: two thirds of the country’s land area is less than five metres above sea level. With 166 million people, it’s one of the poorest and most densely populated countries on Earth – and one of the most threatened by climate change.

A recently released report by the Environmental Justice Foundation (EJF) says rises in sea levels caused by climate change could result in Bangladesh losing more than 10% of its land area by mid-century, resulting in the displacement of 15 million people.

The country is already experiencing some of the fastest-recorded sea level rises in the world, says the EJF, a UK-based organisation that lobbies for environmental security to be viewed as a basic human right.

Unpredictable rains

Increasingly erratic rainfall patterns – linked to changes in climate – are adding to the nation’s problems. Sudden, violent downpours have resulted in rivers breaking their banks and land being washed away.

Rising sea levels mean land and drinking water is contaminated by salt. Farmers are forced to abandon their land and move – many to Dhaka, the capital, one of the world’s so-called megacities, with a population of more than 15 million.

“Bangladesh has a long history of floods, but what used to be a one-in-20-year event is now happening one year in five”, says Saleemul Huq, director of the International Centre for Climate Change and Development in Dhaka. “It is what we would expect with climate change models.”

Farmers further inland are also forced to move to the capital in search of work due to surging rivers eating away their lands. The city’s slums are expanding, and Dhaka’s population is increasing by more than 4% each year.

Farming abandoned

“We had a small farm – we used to produce peanuts and gourd, corn and sugar all year round”, says one farmer quoted in the EJF report. “Now I collect scraps of work as a labourer.”

EJF says climate change should not be seen only as an environmental issue; climate change is also contributing to a rapidly developing humanitarian crisis, not just in Bangladesh but in many other regions around the world.

“It is countries like Bangladesh, and people like those we met, whose contributions to climate change have been among the smallest, that are now facing the worst impacts”, says Steve Trent, EJF’s executive director.

“We must act now to prevent this becoming a full-scale humanitarian crisis.”

“Bangladesh has a long history of floods, but what used to be a one-in-20-year event is now happening one year in five”

In recent months more than 600,000 people – Rohingya refugees from violence in neighbouring Myanmar – have set up shelters in southern Bangladesh. There are fears that this community could also be under threat during the monsoon period.

The EJF report highlights how women in Bangladesh are especially vulnerable to climate-related disasters. In 1991 a cyclone which swept across the Bay of Bengal caused the deaths of 140,000 people and forced 10 million to leave their homes.

EJF says 90% of the dead were women; their lower status means they are often not taught survival skills. Women also tend to stay with children and other family members when disaster strikes.

Those women who do migrate find it more difficult to adapt to life in a Dhaka slum or elsewhere. Some become victims of trafficking, ending up in brothels in India.

Foreign migration grows

EJF says that while most climate migration is internal, there are indications that growing numbers of Bangladeshis are seeking to move outside the country. It says that in early 2017 there was a particularly big surge in the number of Bangladeshi migrants arriving in Italy after completing the perilous journey by land and sea from their homeland.

EJF is calling for the creation of an international legally binding agreement for the protection of climate refugees. The EU should take the lead in this process, it says.

“There should be clarifications on the obligations of states to persons displaced by climate change, with new legal definitions”, says EJF.

“Definitions of climate-induced migration are urgently needed to ensure a rights-based approach and give clarity to the legal status of ‘climate refugees’; these must be developed without delay.” – Climate News Network

Record heat means hurricanes gain ferocity faster

Hurricane forces are accelerating, and devastating floods can be linked to warmer oceans. But climate change is not the only factor.

LONDON, 18 May, 2018 – Hurricanes are becoming more violent, more rapidly, than they did 30 years ago. The cause may be entirely natural, scientists say.

But Hurricane Harvey, which in 2017 assaulted the Gulf of Mexico and dumped unprecedented quantities of rain to cause devastating floods in Texas, happened because the waters of the Gulf were warmer than at any time on record. And they were warmer because of human-driven climate change, according to a second study.

Both studies examine the intricate machinery of a natural phenomenon, the tropical cyclone. Researchers from the Pacific Northwest National Laboratory looked at how fast four of 2017’s hurricanes – Harvey, Irma, Jose and Maria – intensified: episodes in which maximum wind speed rose by at least 25 knots, which is more than 46 kilometres, per hour within a 24-hour period. They report in Geophysical Research Letters that they combed through 30 years of satellite data from 1986 to 2015 to find a pattern.

“As climate change continues, we can expect more supercharged storms like Harvey”

Researchers have repeatedly warned that hurricane hazard must increase with global warming, driven by profligate human combustion of fossil fuels that dump greenhouse gases in the atmosphere. Hurricanes will hit higher latitudes and deliver more damage within the Gulf of Mexico. But climate change is only part of the answer.

The latest study did not find that storms were intensifying rapidly more often than usual. But the researchers did find that when a storm grew at speed, it became much more powerful within a 24-hour period than such storms did 30 years ago: wind speeds had gained 3.8 knots or seven kilometres an hour for each of the three decades.

And although hurricanes are driven by the warmth of the upper ocean, the researchers decided that rather than overall ocean warming, in this case the biggest factor was a natural cycle called the Atlantic Multidecadal Oscillation, which in its present phase tends to make ocean waters warmer in the central and eastern Atlantic – the spawning ground for Irma, Jose and Maria.

Warmest on record

But when Harvey hammered the Texas coast in August 2017, the waters of the Gulf of Mexico were warmer than they had ever been. And scientists from the National Center for Atmospheric Research (NCAR) report in the journal Earth’s Future that they calculated the rate of evaporation as the hurricane winds raced over the water and compared it with the levels of precipitation over the city of Houston.

To make a hurricane happen at all, ocean temperatures need to reach 26°C. When Harvey gathered its strength and its moisture, the Gulf waters had tipped 30°C.

“We show, for the first time, that the volume of rain over land corresponds to the amount of water evaporated from the unusually warm ocean,” said Kevin Trenberth, a senior scientist with NCAR. “As climate change continues, we can expect more supercharged storms like Harvey.” – Climate News Network

Kelp forests under threat from acid seas

The kelp forests – those towering submarine tangles of brown seaweeds – may not survive the steady change of ocean chemistry.

LONDON, 17 May, 2018 – Australian scientists have identified a risk to the kelp forests of the oceans, a new way in which carbon dioxide can change the world. Ever more acidic oceans could encourage weedy submarine grasslands to replace the rich habitats of the coastal kelp forests.

Although most climate change forecasts are based on computer simulation, this one has been tested in the real world. The scientists used natural volcanic seeps rich in carbon dioxide to observe the changes to sea floor ecosystems as water chemistry changes with greater levels of dissolved CO2.

“Carbon emissions might boost plant life in the oceans, but not all plant life will benefit equally,” said Sean Connell, of the Environment Institute at the University of Adelaide.

“Weedy species are quicker to capitalise on nutrients, such as carbon, and can grow faster than their natural predators can consume them.

Weedy turf wins

“Unfortunately, the CO2 that humans are pumping into the atmosphere by burning fossil fuels gets absorbed by the ocean and favours weedy turfs, which replace kelp forests that support higher coastal productivity and biodiversity.”

He and colleagues from Australia, the US, New Zealand, Italy and Hong Kong report in the journal Ecology that they made a series of samples of submarine plant growth at natural volcanic vents in New Zealand’s Bay of Plenty: they looked at rocky reefs on which grew a mosaic of kelp and turf algae, along barren stretches grazed by sea urchins and a native New Zealand mollusc.

They chose the sites because the levels of carbon dioxide – and therefore the measures of acidity – in the water were roughly what climate scientists would predict for the end of this century, if humans go on releasing greenhouse gases.

They found that ecosystems changed with shifts in water chemistry. “While elevated CO2 caused some weeds to be eaten in greater amounts, the dominant sea urchin predator ate these weeds at reduced amounts. This enabled the weeds to escape their natural controls and expand across coasts near the elevated CO2,” Professor Connell said.

“Carbon emissions might boost plant life in the oceans, but not all plant life will benefit equally”

The slow but inexorable changes in ocean acidity will have inevitable consequences for coastal protection offered by natural ecosystems. Kelp forests provide habitat or nourishment for seals, sea otters, sea lions, whales, cormorants, gulls, terns and shore birds as well as fish. There is evidence that warming has already damaged some of Australia’s kelp forests.

Researchers have been issuing such warnings for years: among them Professor Connell and his co-author from Adelaide, Ivan Nagelkerken, who, three years ago, surveyed 632 scientific studies of a huge range of marine habitats to conclude that the overall effect of acidification was to impoverish ocean life.

“Under the level of acidification we will find in the oceans in a few decades, marine life is likely to be dominated by fast-growing and opportunistic species at the expense of longer-lived species with specialist lifestyles, unless we set some change in place,” said Professor Nagelkerken.

“We need to consider how natural enemies might be managed so that those weedy species are kept under control.” – Climate News Network

Coral island freshwater faces pollution risk

People on low-lying coral atolls need not wait until the rising seas lap at their feet. It’s the island freshwater that is first at risk.

LONDON, 10 May, 2018 – For atoll dwellers across much of the world, the island freshwater on which they depend may be in jeopardy within a couple of decades.

The combination of sea level rise and ever more extreme storm conditions – each a consequence of global warming and climate change – could make many of the world’s coral atolls uninhabitable  within one human generation.

Although many of the low-lying islands of the Indian and Pacific Oceans are two metres above sea level, and although in the gloomier scenarios sea levels will rise a metre by 2100, the freshwater resources of such islands are likely to be polluted by the invading seas by about 2050, according to new research.

Worldwide, there are thousands of inhabited atolls and cays, with reaches of coral above the reef waterline long colonised by vegetation, to provide shelter for birds, small animals and people.

“The tipping point when potable groundwater on the majority of atoll islands will be unavailable is projected to be reached no later than the middle of the 21st century”

But as the icecaps and glaciers melt, in response to ever greater greenhouse gas emissions from factory chimneys, power stations and vehicle exhausts, to drive up the planetary thermometer, more freshwater will flow into the oceans, which will anyway expand as temperatures rise.

And since global warming is likely to be accompanied by greater extremes of tropical cyclone and windstorm, islanders everywhere will become increasingly vulnerable.

US scientists report in the journal Science Advances that they decided to look in fine detail at the consequences for one group of atoll-dwellers on Roi-Namur, in the Kwajalein atoll in the Republic of the Marshall Islands.

There are around 1,100 low-lying islands in 29 atolls in the group, and these are home to hundreds of thousands of people. But not, possibly, for much longer.

Dual risk

The researchers considered the projections for gradual sea level rise but focused also on the dynamics of waves as the seas continue to rise, and as ever higher waves driven by ever more energetic storms wash over the low coral structures.

And as these waves batter the coral above the high tide line, so does the likelihood grow that brine will get into the bedrock and poison the natural bedrock aquifers filled with rainwater on which the islanders rely.

Coast-dwellers and people of the lowest-lying islands have the most to lose from climate change, starting with the ground on which they live. Sea level rise has already been identified as a threat for one small settlement off the coast of the US mainland, and future sea level rise could threaten many in the wider Pacific and sweep away tourist investments in the Indian Ocean.

Such findings matter not just for the Marshall Islanders: there are settled atolls in the Caroline, Cook, Line and Society Islands, in the Maldives, the Seychelles and the Hawaiian Islands. All could be vulnerable.

Little choice

“The tipping point when potable groundwater on the majority of atoll islands will be unavailable is projected to be reached no later than the middle of the 21st century,” said Curt Storlazzi, of the US Geological Survey, who led the research.

The damage from flooding to the islands’ homes, stores and workshops, combined with the loss of freshwater, will start to make human habitation difficult in many such islands by between 2030 and 2060, and go on doing so.

Either the islanders must find the money to secure their water supply and protect their homes, or they must abandon their homelands. What oceanographers call overwash – the great waves that occasionally splash right across the narrow atolls – will become more frequent, and more damaging.

“The overwash events generally result in salty ocean water seeping into the ground and contaminating the freshwater aquifer. Rainfall later in the year is not enough to flush out the saltwater and refresh the island’s water supply before the next year’s storms arrive, repeating the overwash events,” said Stephen Gingerich of the USGS, a co-author. – Climate News Network

UK and US scientists tackle Antarctic glacier

British and American scientists are joining forces to research the melting of an Antarctic glacier in what they are calling a race against time. 

CAMBRIDGE, UK, 30 April, 2018 – An international team of scientists is mounting an ambitious research programme to find how soon a vast Antarctic glacier may collapse, with implications for sea levels worldwide.

The Thwaites Glacier in West Antarctica could significantly affect global sea levels. It already drains an area roughly the size of Britain or the US state of Florida, accounting for around 4% of global sea-level rise, an amount that has doubled since the mid-1990s. Its collapse would destabilise other parts of the ice sheet.

If – or more likely when – Thwaites and its neighbour, the Pine Island glacier, ultimately lose all their ice, one estimate suggests that could raise global sea levels by about 3.4m, enough to affect every coastal city on Earth.

Fastest-moving

Satellites have shown for more than a decade that the Thwaites region is an area of massive change and rapid ice loss as the global climate warms in response to rising greenhouse gas emissions from humans’ profligate use of fossil fuels. The two glaciers are among the fastest-moving in the Antarctic.

One of the scientists involved in the research is David Vaughan, director of science at the Cambridge-based British Antarctic Survey (BAS). He says he and his colleagues are involved in “a race against time”.

Professor Vaughan told the Climate News Network: “Understanding sea level rise is the front line of climate change, and sea level rise doesn’t happen overnight. [What’s happening to Thwaites] is not an emergency this year, but I’m very glad we’re doing the research this decade, because we can’t wait too long.”

Understanding collapse

As part of a new £20 million (roughly US$27.5m) research collaboration, the UK Natural Environment Research Council and the US National Science Foundation are about to send a team of scientists to Antarctica to gather the data needed to understand when the collapse of the Thwaites glacier could begin – in centuries, or in the next few decades.

NERC and NSF are jointly funding eight large-scale projects that will bring together leading polar scientists in the International Thwaites Glacier Collaboration (ITGC), the largest joint project undertaken by the two nations in Antarctica for more than 70 years. The ITGC involves around 100 scientists from leading research institutes in both countries with researchers from South Korea, Germany, Sweden, New Zealand and Finland.

There are signs that the process of Thwaites’ collapse has already begun. Antarctica’s glaciers add to sea-level rise when they lose more ice to the ocean than they gain from snowfall. To fully understand the causes of changes in ice flow requires research on the ice itself, the nearby ocean, and the Antarctic climate.

“Sea level rise doesn’t happen overnight. [It’s] not an emergency this year, but I’m very glad we’re doing the research this decade, because we can’t wait too long”

The Collaboration will use drills that can make access holes 1,500 metres into the ice with jets of hot water, as well as other state-of-the-art techniques and equipment, such as autonomous submarines like the Autosub Long Range, the first of whose fleet is named Boaty McBoatface.

While NERC is funding the UK’s share of the project, it is being co-ordinated by BAS, whose total annual budget is around £50m. The agency co-ordinating the US share is the National Snow & Ice Data Center.

As well as the cost of the research itself, the physical problems of mounting a scientific campaign in one of the most remote places in Antarctica could cost as much again in logistical support. The nearest permanently occupied research station to the Thwaites glacier is more than 1,600km away, so even getting the scientists to where they need to be will be demanding.

Collaboration welcome

Researchers on the ice will rely on aircraft support from UK and US research stations, but oceanographers and geophysicists will approach the glacier from the sea in British and American research icebreakers.

The UK’s science minister, Sam Gyimah, said: “Rising sea levels are a globally important issue which cannot be tackled by one country alone. The Thwaites glacier already contributes to rising sea levels, and understanding its likely collapse in the coming century is vitally important.”

The five-year programme begins in October this year and continues to 2023. Its data will be archived and freely shared when it ends. – Climate News Network

Plastic particles now infest the Arctic

Tiny plastic particles have been found in every sample collected of Arctic sea ice. But the ice can only hold these indestructible pollutants for so long.

LONDON, 27 April, 2018 – Plastic particles have colonised one of the last  once-pristine oceans. German scientists sampled sea ice from five locations within the Arctic Circle and counted up to 12,000 microscopic particles per litre of ice.

They have even been able to identify the sources and piece together the journey to the icy fastness. Some tiny lumps of plastic detritus have made their way north from what has become known as the Great Pacific Garbage Patch, a swirling assembly of an estimated 80,000 tons of plastic floating in the ocean across a stretch of water bigger than France.

Other fragments, that began as paint and nylon, date from the invasion of increasingly ice-free Arctic summer waters by more freight ships, and more fishing vessels, the scientists report in the journal Nature Communications.

“During our work, we realised that more than half of the microplastic particles trapped in the ice were less than a twentieth of a millimetre wide, which means they could easily be ingested by Arctic micro-organisms like ciliates, but also by copepods,” said Ilka Peeken, a biologist with the Alfred Wegener Institute.

“Microplastics are now ubiquitous within the surface waters of the world’s oceans.  Nowhere is immune”

“No one can say for certain how harmful these tiny plastic particles are for marine life, or ultimately also for human beings.”

The researchers gathered their samples during three expeditions to the Arctic aboard the icebreaker Polarstern in the spring of 2014 and the summer of 2015, following an ice movement called the Transpolar Drift from Siberia as far as the Fram Strait where warm Atlantic water enters the polar ocean. The Transpolar Drift was first identified by the Norwegian explorer Fridtjof Nansen aboard the Fram, late in the 19th century.

Microplastic particles are defined as 5mm or smaller, and many are measured in millionths of a metre. These are formed by the deterioration of larger pieces of plastic dumped into landfills in billions of tonnes, or released into the waterways and thus into the ocean.

Man-made synthetic polymers are effectively indestructible, and now represent a major source of marine pollution and a constant hazard to wildlife.

More than two-thirds of the particles measured 50 millionths of a metre or smaller. Some were as small as 11 micrometres – one sixth of the diameter of a human hair.

Multiple sources

The researchers identified 17 different types of plastic in the sea ice: from paints, nylon, polyester, cellulose acetate – used in cigarette filters – and the packaging materials polyethylene and polypropylene.

The guess is that the plastics endure in the sea ice for between two and 11 years before melting from their icy packaging in the Fram Strait, to begin sinking in deeper waters. One study recently found 6,500 bits of microplastic per kilogram sampled from the sea floor.

“This is an important finding because it means that they were always present in the water under the ice as it was growing, and drifting, within the Arctic Ocean,” said Jeremy Wilkinson, a sea ice physicist with the British Antarctic Survey, commenting on the study.

“Sea ice grows from the freezing of seawater directly onto the bottom of the ice (i.e. it grows vertically downwards), thus it was incorporating microplastic particles as it grew. It suggests that microplastics are now ubiquitous within the surface waters of the world’s oceans.  Nowhere is immune.” – Climate News Network

Arctic currents change as ancient Pacific did

Changes in Arctic currents today appear to reflect similar changes thousands of years ago – in the North Pacific. Scientists think they may be linked.

LONDON, 26 April, 2018 – The recent discovery that Arctic currents have weakened significantly appears in some ways to be a repeat of what happened the other side of the Arctic in the distant past.

Thousands of years ago the circulation of the North Pacific ocean changed  substantially, releasing large quantities of carbon dioxide to the atmosphere, scientists in Scotland have found.

The change they have identified helped to warm the planet and to end the last Ice Age. It happened about 15,000 years ago, though, so it should be of little concern to us today – except for one factor.

Several weeks ago an international scientific study published new and harder evidence that one of the planet’s key heat pumps, the currents which exchange warmth between the tropics and the Arctic, are weaker today than at any time in the last millennium.

“Humans have driven CO2 rise in the atmosphere as large as the CO2 rise that helped end the last Ice Age, but the man-made CO2 rise has happened 100 times faster. This will have a huge effect on the climate system”

While earlier studies of northern ocean currents had relied on computer simulations, this later study is different: it is based on direct observation of what is actually happening in the Atlantic and Arctic oceans.

And what’s happening there now is not markedly different from what took place long ago in the North Pacific. The researchers think their findings are strong enough to suggest a possible link, one which if established could have essential information for this generation.

The Scottish study, published in the journal Nature Geoscience, also found that the changes in circulation resulted in a reduction of the amount of oxygen in the deep ocean. The findings will help scientists to understand the processes controlling the exchange of CO2 and oxygen between the ocean and atmosphere.

The researchers measured the chemical composition of the shells of tiny fossil plankton, called foraminifera, which they used to reconstruct the exchange of CO2 between the North Pacific ocean and atmosphere at the end of the last Ice Age, when carbon dioxide levels in the atmosphere increased.

Circulation change

They found that the North Pacific had released large amounts of CO2 to the atmosphere around 15,000 years ago, when ocean currents in the Atlantic were also changing rapidly.

Their findings showed that the release of CO2 by the North Pacific was caused by a change in its circulation and could explain a drop in oxygen levels in the Pacific which occurred at the same time and was first discovered over 20 years ago. Scientists are seeing a similar loss of oxygen from the ocean as the climate changes today.

The lead author, Dr Will Gray, from the School of Earth and Environmental Sciences at the University of St Andrews but formerly of University College London, said the new studies showing that ocean currents in the North Atlantic were slowing down were “worrying”.

He said: “In our study we see very rapid changes in the climate of the North Pacific that we think are linked to past changes in ocean currents in the Atlantic. This gives us an example of the way that different parts of the climate system are connected, so that changes in circulation in one region can drive changes in CO2 and oxygen all the way over on the other side of the planet.

Future need

“The North Pacific ocean is very big and just below the surface the waters are brimming with CO2; because of this, we really need to understand how this region can change in the future, and looking into the past is a good way to do that.”

US scientists found several years ago that in a single decade the North Atlantic had increased by 50% the rate at which it was absorbing CO2 from human activities.

Dr Gray’s co-author Dr James Rae, also from the University of St Andrews, said that although the ancient North Pacific CO2 rise was dramatic in geological terms, it happened very slowly compared to modern man-made CO2 rise.

“Humans have driven CO2 rise in the atmosphere as large as the CO2 rise that helped end the last Ice Age, but the man-made CO2 rise has happened 100 times faster”, he said. “This will have a huge effect on the climate system, and one that we are only just beginning to see.” – Climate News Network

Hopes rise for some coral survival

US scientists have good news about prospects for coral survival on one of the world’s great reefs, threatened by climate change.

LONDON, 25 April, 2018 – Researchers have raised hopes that limited coral survival may be possible, allowing one of the world’s best-known reefs to survive a little longer.

Although corals are highly sensitive to ocean warming, and notoriously bleach when temperatures exceed a certain limit, a new study has shown that at least one coral can evolve tolerance to excessive temperatures.

The implication is that even though other teams have repeatedly warned that the world’s reefs are in peril as the world warms because of ever-greater ratios of greenhouse gases in the atmosphere, as a consequence of human combustion of fossil fuels at a profligate rate, the world’s great reefs may survive for perhaps another century, rather than perish within the next 50 years.

“It means these corals will still go extinct if we do nothing,” said Misha Matz, of the University of Texas at Austin, who led the study. “But it also means we have a chance to save them. It buys us time to actually do something about global warming, which is the main problem.”

The argument is based on Darwinian logic: coral colonies produce colossal numbers of larvae each year, set adrift on ocean currents to colonise new reefs. As conditions change, those corals that by an accident of genetic inheritance have the traits needed to cope with environmental challenge will get a foothold, and flourish. Those that don’t will fade out. Natural selection will respond.

”While the fact that one species may do well is good news, there are many other reef organisms that may fare far worse, so it is easy to envisage a future with a few winners but many losers”

And this is hopeful news, if only because the world’s reefs are under threat as never before. Bleaching – the response to heat in which coral rejects the algae with which it normally lives in symbiosis – has always happened: research earlier this year suggests it could become five times more frequent, and reefs such as Australia’s Great Barrier would have no time to recover.

Some reefs have already been pronounced too damaged ever to be restored. This is bad news not just for the coral animals: the tropical reefs are just about the richest habitats on the planet, and of profound economic importance to humans too.

A partnership of US and Australian scientists reports in the Public Library of Science journal PLOS Genetics that computer simulation models and genetic evidence of variation from one species of staghorn coral, called Acropora millepora, together show that the coral could in theory adapt over a stretch of 20 to 50 generations.

“This genetic variation is like fuel for natural selection,” Dr Matz said. “If there is enough of it, evolution can be remarkably fast, because all it needs to do is reshuffle the existing variants between the populations.

“It doesn’t have to wait for a new mutation to appear; it’s already there. The problem is, when the genetic variation is exhausted, it is over and the future is unclear.”

Tentative conclusions

There are problems with such studies. This one is based on genetic evidence from one species of coral. But the 2,300 km Great Barrier Reef of Australia is home to at least 411 species of hard coral. It is based on a mathematical model, not on observed change in the reefs.

And global warming is not the only challenge to coral reefs, which are also threatened by human exploitation, pollution and increasing acidification  of the surrounding seas, again as a consequence of ever higher levels of carbon dioxide in the atmosphere.

“Corals live in a symbiotic relationship with zooxanthellae, which are plant-like cells hosted in surface tissues that provide up to 90% of the energy to the colony,” said Stephen Simpson, a marine biologist at the University of Exeter in the UK, commenting on the study.

“Whether there is also sufficient genotypic variation in the zooxanthellae to tolerate further warming remains to be seen. While the fact that one species may do well is good news, there are many other reef organisms that may fare far worse, so it is easy to envisage a future with a few winners but many losers, threatening the functional integrity of reef ecosystems.” – Climate News Network

North Atlantic ocean currents are slowing

The North Atlantic currents which help to warm north-west Europe have slowed significantly since the last century, scientists confirm.

LONDON, 12 April, 2018 – The Gulf Stream is slowing, the North Atlantic is cooling. An international scientific study has found new and harder evidence that one of the planet’s key heat pumps, the currents which exchange warmth between the tropics and the Arctic, are weaker today than at any time in the last thousand years.

The currents, known as the Atlantic overturning – its scientific name is the Atlantic Meridional Overturning Circulation, the AMOC – bring warm water north from the tropics and return south with cold water.

Earlier studies suggested strongly that any weakening of the AMOC would speed sea level rise on the US east coast and cool north-west Europe by up to 5°C.

Those studies made use of computer simulations. But the latest research is radically different. It is based on direct observation of what is happening in the ocean. And it is, in non-scientific language, hard evidence that the Gulf Stream is slowing down.

”The specific trend pattern we found in measurements looks exactly like what is predicted by the computer simulations as a result of a slowdown in the Gulf Stream system”

A team from Germany’s Potsdam Institute for Climate Impact Research (PIK) and the US National Oceanic and Atmospheric Administration has found evidence which it says not only supports the earlier predictions, but makes them hard to dispute.

In a study published in the journal Nature the researchers say analysis of sea surface temperature data shows that the AMOC has slowed down by roughly 15% since the middle of the 20th century, with human-made climate change a prime suspect.

“We detected a specific pattern of ocean cooling south of Greenland and unusual warming off the US coast – which is highly characteristic for a slowdown of the Atlantic overturning, also called the Gulf Stream system,” said the lead author, Levke Caesar from PIK. “It is practically like a fingerprint of a weakening of these ocean currents.”

For decades computer simulations have generally predicted that the AMOC will weaken in response to human-caused global warming. But whether this is already happening has until now been unclear, because of a lack of long-term direct current measurements.

Most robust

Not any more, though. “The evidence we’re now able to provide is the most robust to date,” says Stefan Rahmstorf of the Potsdam Institute, who conceived the study. “We’ve analysed all the available sea surface temperature data sets, comprising data from the late 19th century until the present.”

“The specific trend pattern we found in measurements looks exactly like what is predicted by the computer simulations as a result of a slowdown in the Gulf Stream system, and I see no other plausible explanation for it.”

The Atlantic overturning is driven by the differences in the density of the ocean water: when the warm, lighter water flows from south to north it becomes colder, denser and heavier, making it sink deeper and flow back southwards.

Global warming is not the only influence on the AMOC. Increased rainfall and meltwater from the Arctic sea ice and Greenland ice sheet are also diluting the waters of the northern Atlantic, reducing the salinity. Less saline water is less dense and so less heavy, making it harder for the water to sink from the surface to the ocean depths.

Second study

There have been long debates about whether the AMOC could collapse, which would constitute a tipping element in the Earth system. The PIK study does not consider the AMOC’s future, instead analysing how it has changed over the past century.

A second study, by a team including David Thornalley, from University College London,  in the same issue of Nature, looks into the Earth’s past climate to reconstruct Atlantic overturning changes over the past 1,600 years.

It provides independent confirmation for earlier conclusions that the weakness of the circulation today is unprecedented for more than a millennium at least.

“Several lines of evidence are coming together to a consistent picture now, all pointing at the same weakening since the 1950s,” says Professor Rahmstorf: “[They include] sub-polar Atlantic cooling, the warming inshore of the Gulf Stream, Thornalley’s proxy data for subsurface Atlantic temperatures, and earlier proxy data from deep sea corals showing water mass changes in the Gulf of Maine.” – Climate News Network

Inaction on marine pollution faces challenge

Marine pollution from ships’ engines is adding significantly to greenhouse gas emissions, and is growing. But global pressure for change is growing too.

LONDON, 9 April, 2014 – The International Maritime Organisation (IMO), the United Nations body responsible fo preventing  marine pollution by ships, starts a five-day meeting at its London HQ today. A glance at the agenda suggests it will need far longer than that to make much headway.

A 2014 IMO report found that, between 2007 and 2012, global shipping produced an annual average of 866 million tonnes of CO2 equivalent – 2.4% of global greenhouse gas emissions over that period. Those emissions are expected to grow between 50 and 250% by 2050.

A European Parliament report in 2015 said shipping could account for as much as 17% of global carbon emissions by 2050. That year the Parliament outlined plans for the maritime industry to be included in the European Union’s Emissions Trading System, a cap-and-trade scheme aimed at tackling global warming.

So when the IMO’s marine environment protection committee, the MEPC, tackles one of the main items before it, the reduction of greenhouse gas emissions from ships, it will have its work cut out.

”International shipping is the backbone of our global trading system. But it can no longer be given a free pass on climate change”

One main reason is simple inertia, the inability – or perhaps unwillingness – of a global industry to contemplate new ways of doing things.

The European Environment Agency published a report in January on the impacts of both aviation and shipping on Europe’s environment. Neither sector was included in the 2015 Paris Agreement on climate change.

The EEA says bluntly that trying to improve the present approach will not work: “…incremental measures such as improving fuel efficiency to cut emissions will not be enough…to meet European greenhouse gas emissions and sustainability targets.”

What’s needed instead, says the EEA, is “a massive shift in innovation, consumer behaviour and the take-up of more ambitious green technologies to power aircraft and seafaring cargo ships.”

It acknowledges that both industries face “complex challenges” in reducing their environmental impacts and in many ways are locked into established ways of operating which can be difficult to change.

Tax breaks

For example, it says, past investments in conventional airport and seaport infrastructure can delay the introduction of more sustainable technologies and opportunities to encourage alternative cleaner transport like rail.

The long lifespan of aircraft and ships can also slow the pace of change, and the report says there is a lack of research on cleaner fuels for both aircraft and ships, let alone the costs involved in producing them.

Besides these obstacles to change, the EEA says both international aviation and shipping benefit from significant tax exemptions on fossil-based fuels, which can act as a further barrier.

The report says governments have a key role to play by supporting investment in research, product standards and subsidies for new emerging technologies.

Lifestyle choices

Citizens too should be involved, the EEA says: it wants more debate on sustainable travel and consumer behaviour, and says changes to lifestyles and transport habits can also help in the long term to reduce carbon emissions and other aviation and shipping impacts.

It notes that transport, including aviation and shipping, continues to be a significant source of air pollution.

But if inertia is delaying action on cleaning up global shipping, it doesn’t have to: there are practical solutions already available. As long ago as  2009 an IMO report said: “A significant potential for reduction of GHG [greenhouse gases] through technical and operational measures has been identified.

“Together, if implemented, these measures could increase efficiency and reduce the emissions rate by 25% to 75% below the current levels. Many of these measures appear to be cost-effective…”

Arctic risk

A particular issue of concern on the MEPC’s agenda is the continuing use of heavy fuel oil in the Arctic, where a spill or other accident could cause drastic pollution.

Both the use and the transport of the oil is banned in the Antarctic, and the IMO’s Polar Code recommends that the same rules should be applied to the Arctic as well.

The need to act is urgent, say those directly affected and the climate experts who support them. An article in the New York Times last week was written jointly by Hilda Heine, the president of the Republic of the Marshall Islands, and Christiana Figueres, formerly the executive secretary of the UN Framework Convention on Climate Change.

They wrote: “International shipping is the backbone of our global trading system. But it can no longer be given a free pass on climate change…

“To achieve the goals of the Paris Agreement and to avoid the most devastating impacts of climate change across the globe, we cannot forget about international shipping. The world needs to take notice.” – Climate News Network