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by Paul Brown

Clouds ‘cool Earth less than thought’

May 17, 2013 in Science

EMBARGOED until 2301 GMT on Thursday 16 May

Clouds may temper global warming less than thought: So what is? Image: Ave Maria Mõistlik

Clouds may temper global warming less than thought: So what is?
Image: Ave Maria Mõistlik

By Paul Brown

The ability of clouds to reflect sunlight back into space and so help to cool the Earth appears to have been over-estimated, researchers say, in a study especially significant for major polluters.

LONDON, 17 May – Extra cloud cover caused by emissions of industrial pollutants is known to reduce the effects of global warming, but its impact in reducing temperatures has been over-estimated in the climate models, new research has found.

This is particularly significant for China and India, because it has been believed that these two giant countries would be partly shielded from the effects of climate change by their appalling industrial pollution. The Max Planck Institute for Chemistry in Germany believes this potential cooling effect has been exaggerated.

The Institute’s study looked at the behaviour of sulphate particles in the air created by the reaction of oxygen with sulphur dioxide released from factory chimneys and other sources of pollution.

In humid conditions the sulphates attract water droplets and form clouds. This increase in the cloud cover reflects more sunlight back into space and so cools the earth.

The Max Planck researchers went to study a cloud formed at the top of a mountain, taking samples at various times to see how the sulphates reacted progressively.  What was crucial was how the sulphates were formed in the first place.

Current climate models assume that hydrogen peroxide and ozone have a large role in creating the sulphates, but the new research shows that the catalysts for the chemical reaction are more likely to be metal ions like iron, manganese, titanium or chromium.

The key factor is that all of these are heavier than hydrogen peroxide and ozone, and because of this are more likely to fall out of the cloud through the pull of gravity, thus considerably reducing the cooling effect of the original pollution.

Less time aloft

 

Eliza Harris and Bärbel Sinha, with a number of other scientists, captured the air samples and examined the isotopes in a mass spectrometer.

Harris, who was recently awarded the Dieter Rampacher Prize as the youngest doctoral candidate of the Max Planck Society, said: “The relative reaction rates of isotopes are like fingerprints, which tell us how the sulphate was formed from the sulphur dioxide.

“As my colleagues and I compared the basic assumptions of climate models with my results we were very surprised, because only one of twelve models considers the role of transition metal ions in the formation of sulphate”, said Harris, who is now working at the Massachusetts Institute of Technology (MIT) in the USA.

Because of the extra size of the sulphates and hence their greater weight, compared with the previous assumptions, she believes that climate models have over-estimated the cooling effect of the sulphate aerosols by assuming they would stay airborne longer.

So far the findings have not been factored into calculations on the regional effect of climate change. Harris says that in Europe, where pollution from industrial processes is already on the decline, the change in the calculations on warming would be relatively small.

However, in the growing industrial giants like India and China, where coal-fired power stations and other forms of industrial pollution are throwing out sulphur dioxide at an ever-greater rate, then the effect could be considerable. Further research on this is continuing. - Climate News Network

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by Kieran Cooke

Ground slows glacier ice loss

May 12, 2013 in Science

EMBARGOED until 2301 GMT on Sunday 12 May

One of the valley walls of the Petermann glacier in northern Greenland Image: NASA/Michael Studinger

One of the valley walls of the Petermann glacier in northern Greenland
Image: NASA/Michael Studinger

By Kieran Cooke

New understanding of some of Greenland’s major glaciers suggests they may not melt in the future nearly as fast as they are doing now.

LONDON, 13 May – Scientists tread very carefully when it comes to glaciers. While the consensus is that glaciers around the world are generally in retreat, there are the exceptions:

in the west of the Himalayas some glaciers have been found to be growing, not shrinking. In Antarctica some glaciers are gaining mass balance while others are losing it. Meanwhile glaciers in other parts of the world, particularly in the Andes,  are disappearing at an ever increasing rate.

The impact of climate change on the Greenland ice sheet has been well documented: Arctic temperatures are rising at levels well above the global average, and ice-loss has been accelerating.

This has raised concerns that these constantly increasing rates of ice loss will lead to a rise in sea levels that could threaten coastal communities around the world. Yet the future contribution of Greenland’s glaciers to sea-level rise is uncertain.

A new study published in the journal Nature questions whether present trends of ice loss on the Greenland ice sheet will be maintained.

The report – Future Sea-level Rise from Greenland’s Major Outlet Glaciers in a Warming Climate – looks at the behaviour of the four major fast flowing glaciers in Greenland. The Petermann, Kangerdlugssuaq, Helheim and Jakobshavn glaciers together drain about 22% of the island’s ice sheet.

Lower loss expected

 

By building up a computer model of these four glaciers, scientists have revealed that the shape of the ground beneath the ice has a marked impact on the way the ice moves, with the rate at which the glaciers are losing ice depending critically on the shape of the fjords in which they sit and the topography of the rock below them.

In turn, this has led the scientists to doubt whether present rates of ice loss and the “calving” of icebergs from the glaciers will be maintained.

“…While these glaciers may show several bursts of retreat and periods of high iceberg formation in future, the rapid acceleration seen in recent years is unlikely to continue unchecked”, says the report.

The computer model suggests that, because of the influence of various topographical features, the projected sea level rise from ice loss of these four glaciers will be of the order of between 2cm and 5cm by 2200 – considerably lower than previous estimates which have been based solely on the extrapolation of current trends.

However, the rate of  calculated ice loss will still be considerable: the model predicts that the combined ice loss of the four will amount to between 30 gigatonnes (Gt) and 47Gt per year over the present century. One Gt of ice is equivalent to one cubic kilometre of water. By way of comparison, Lake Geneva contains 90Gt of water.

More clarity needed

 

“I am excited by the way we have managed to create a detailed picture of the workings of the glaciers”, says Dr Faezeh Nick, of the Universite Libre de Bruxelles, lead author of the study.

“It turns out that if the fjord a glacier sits in is wide or narrow, it really affects the way the glacier reacts. The important role of the terrain below the ice shows we need to get a much clearer picture of the rest of Greenland’s glaciers before we have the whole story.”

Work on the modelling of the glaciers was carried out under the EU-funded Ice2sea programme which links scientific expertise among 24 institutions in Europe and elsewhere.

Professor David Vaughan, head of the programme, told Climate News Network that though there were various ways of analysing the behaviour of glaciers, the new computer modelling could be vital in assessing future levels of ice loss.

“The key point is that we actually need to know about the land beneath the ice if we are going to come up with really good projections on future ice loss and the contribution to sea level rise of these glaciers. This computer modelling could be a big step forward and adds to our understanding of how glaciers behave.” – Climate News Network

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by Tim Radford

Fast emissions cuts could save species

May 12, 2013 in Science

EMBARGOED until 1700 GMT on Sunday 12 May

Animals like this Arctic fox need snow for their survival Image: Morehouse Keith, US Fish and Wildlife Service

Animals like this Arctic fox rely on the snow for their survival
Image: Morehouse Keith, US Fish and Wildlife Service

 

By Tim Radford

Acting quickly to reduce greenhouse gas emissions could provide more time for many species to adapt to the different conditions which climate change will bring to the zones where they can survive.

LONDON, 12 May – Without serious action to limit global warming, more than half of all land plants and a third of all animals could find their living space dramatically reduced later this century.

That is, if global average temperatures rise by 4°C the climatic regions in which these creatures thrive will shift towards the poles, habitats will dwindle, ecosystems will alter, and ever greater numbers of species will struggle to survive in ever more constrained conditions.

That’s the bad news. The somewhat less bad news is that stringent and dramatic reductions in greenhouse gas emissions could buy time: about another four decades in which humanity’s fellow species could adapt to new circumstances.

Rachel Warren of the University of East Anglia and colleagues in the UK, Australia and Colombia report in Nature Climate Change that they used a 21st century creation, the Global Biodiversity Information Facility (GBIF), based in Copenhagen, Denmark, to examine the known ranges and habitats of more than 48,000 species of plant and animal and tried to calculate how these would be affected by “business as usual” scenarios for greenhouse gas emissions.

The GBIF provides access to 400 million biodiversity records from 10,000 datasets of common plants, mammals, birds, reptiles and amphibians provided by 460 research institutions around the world: the researchers sampled less than half of these.

They concluded that 55% of plants and 35% of animals could have their climatically suitable range at least halved by the 2080s. Unrestricted growth in carbon emissions could be expected to result in large contractions of range, even amongst common and widespread species.

However, losses could be reduced by 60% if, through mitigation policies, the growth in emissions is halted in 2016 or by 40% if halted in 2030.

Sheltering snow

 

The proposition that global warming provides a threat to other species of creature is not new, and should not be surprising. In April researchers warned that climatic zones would shift rapidly as temperatures soar.

Rare plant species in high mountain regions at the limit of their temperature range can hardly migrate downhill when conditions become uncomfortably warm. Coral reefs in the tropics provide shelter and habitat for a huge range of species, but if the corals bleach as the seas warm, then rarer species could vanish altogether.

The loss of Arctic sea ice, notoriously, puts large terrestrial predators such as the polar bear at a disadvantage. If rainforests begin to parch, then the rare species that make their homes there will become even rarer.

In January 2004, Chris Thomas of the University of Leeds and colleagues reported in Nature that climate change could provide stresses that could put at risk the survival of up to a million species: a quarter of all land plants and animals could face oblivion by 2050.

A new report, just published in Frontiers in Ecology and the Environment, looks at the effect of climate change on what the authors call “the subnivium”: that ecosystem composed of plants and animals that sit out the worst of winter under a sheltering blanket of snow.

The spring melt now occurs on average two weeks earlier, and northern hemisphere snow cover in March and April has diminished on average by more than three million square kilometres, according to a team from the University of Wisconsin-Madison.

This apparent mellowing of conditions is in fact bad news for reptiles than can survive buried in the snow, but not, for instance, exposed to biting winds, sudden late frosts and blizzards; plants too that begin to grow too early can be killed off or diminished by the return of harsh conditions.

Snow offers a stable micro-environment in which insects, reptiles, mammals and plants are at least safe from sudden change. If the snow retreats too soon, then plants and animals perish, and migrating bird species that depend on a diet of spring insects are also at risk.

Buying time

 

“There are thresholds beyond which some organisms just won’t be able to make a living”, says the lead author, Jonathan Paul, a forest ecologist. “The subnivium provides a stable environment, but it is also extremely delicate. Once that snow melts, things can change radically.”

But this, once again, is research about the impact of global warming on creatures that already survive under precarious conditions.

Many creatures are at risk of extinction simply because of loss of habitat, pollution, hunting, overfishing and the conversion of wilderness to agricultural lands, and all the other consequences of rapid human population growth:  global warming is just another potential stress for an already endangered animal or plant.

Rachel Warren’s study in Nature Climate Change makes no predictions about extinction: it simply looks at what warming could do to climatic habitats.

Her argument is simply that by cutting emissions immediately and slowing warming during this century to 2°C, these losses could be reduced, and could buy another four decades for species to adapt to the next 2°C rise.

“While there has been much research on the effect of climate change on rare and endangered species, little has been known about how an increase in global temperature will affect more common species”, she says.

“Our research predicts that climate change will greatly reduce the diversity of even very common species found in most parts of the world. This loss of global-scale diversity would significantly impoverish the biosphere and the ecosystem services it provides.” – Climate News Network

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by alex kirby

Amazon ‘may lose 65% of land biomass by 2060′

May 10, 2013 in Science

EMBARGOED until 2301 GMT on Thursday 9 May

Irreplaceable forest may be lost, for no gain at all Image: By Sascha Grabow www.saschagrabow.com

Irreplaceable forest may be lost, for no gain, and the climate will feel the impact
Image: Sascha Grabow www.saschagrabow.com

By Alex Kirby

Making more land in the Amazon available for farming and ranching means felling more trees to make space – and researchers say that risks meaning that more agricultural expansion will simply mean less production, because of deforestation’s effect on the climate.

LONDON, 10 May – There will be no winners if agriculture made possible by widespread felling in the Amazon continues to expand, say researchers from Brazil and the US.

They calculate that the large-scale expansion of agriculture at the expense of the forest could entail the loss of almost two-thirds of the Amazon’s terrestrial biomass by later this century.

Their study, published in the journal Environmental Research Letters, shows that deforestation will not only reduce the capacity of the Amazon’s natural carbon sink.

It will also cause climate feedbacks that will decrease the productivity of pasture and soybeans – the reason advanced for felling the trees in the first place.

Brazil is under intense pressure to convert the Amazon forests to produce crops and provide pasture for cattle. But the forests’ natural ecosystems sustain wild food production, maintain water and other resources, regulate climate and air quality and ameliorate the impact of  infectious diseases.

The researchers are from the Brazilian federal universities of Viçosa, Pampa, Minas Gerais and the Woods Hole Research Center in the US.

They used model simulations to assess how the agricultural yield of the Amazon would be affected under two different land-use scenarios: one, business-as-usual, where recent deforestation trends continue and new protected areas are not created; and the other a governance scenario, which assumes Brazilian environmental legislation is implemented.

They predict that by 2050 a decrease in precipitation caused by deforestation will reduce pasture productivity by 30% in the governance scenario and by 34% in the business-as-usual scenario.

They say increasing temperatures could cause a reduction in soybean yield by 24% in the governance scenario and by 28% under the business-as-usual scenario.

It is significant that the study finds relatively little difference between the outcomes of the two scenarios, perhaps suggesting that Brazil needs to tighten its environmental legislation drastically and to enforce it more effectively.

“…it was a surprise to us that high levels of deforestation could be a no-win scenario – the loss of environmental services from the deforestation may not be offset by an increase in agricultural production”

Perhaps the authors’ starkest conclusion (but see our story of 11 March) is that a combination of the forest biomass removal itself, and the resulting climate change, which feeds back on ecosystem productivity, could result in biomass on the ground declining by up to 65% for the period 2041-2060.

And all this would achieve little or nothing in terms of food production. The researchers write: “…total agricultural output may either increase much less than expected proportional to the potential expansion in agricultural area, or even decrease, as a consequence of climate feedbacks from changes in land use.

“These climate feedbacks, usually ignored in previous studies, impose a reduction in precipitation that would lead agricultural expansion in Amazonia to become self-defeating: the more agriculture expands, the less productive it becomes.”

The lead author of the study, Dr Leydimere Oliveira, said: “We were initially interested in quantifying the environmental services provided by the Amazon and their replacement by agricultural output.

“We expected to see some kind of compensation or off-put, but it was a surprise to us that high levels of deforestation could be a no-win scenario – the loss of environmental services from the deforestation may not be offset by an increase in agricultural production.”

The study shows that the effects of deforestation will be felt most in the eastern Pará and northern Maranhão regions. Here the local precipitation appears to depend strongly on the forests, and changes in land cover would drastically affect the local climate, possibly to the point where agriculture became unviable.

“There may be a limit to the expansion of agriculture in Amazonia. Below this limit, there are not important economic consequences”, said Dr Oliveira.

“Beyond this limit, the feedbacks that we demonstrated start to introduce significant losses in agricultural production.” – Climate News Network

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by Paul Brown

Pollution helps clouds to slow warming

May 8, 2013 in Science

FOR IMMEDIATE RELEASE

Traffic and industry can help clouds to become more reflective

Traffic and industry can help clouds to become more reflective

By Paul Brown

 Unexpected, perhaps, but true – clouds are sending more sunlight back out into space because pollution from human activities is making them more reflective.

LONDON, 8 May – Manmade pollution from vehicle exhausts and factories is having the unexpected effect of cooling the atmosphere by making clouds brighter and so reflecting more sunlight back into space, say researchers from Manchester University, UK.

The role of clouds in climate change as the world warms is one of the great uncertainties of science. The findings, published in Nature Geoscience, are a considerable advance in showing how humans are influencing the climate.

NASA, which runs the US space programme, says that clouds have an enormous impact on the Earth’s climate, reflecting back into space one third of the total amount of sunlight that would otherwise warm the planet.

“Because clouds are such powerful climate actors, even small changes in average cloud amounts, locations, and type could speed warming, slow it, or even reverse it”, NASA says.

Clouds are made up of tiny water droplets suspended in the air. These can begin from natural particles like sea spray or dust but can also be formed from man-made pollutants from vehicle exhausts or factory chimneys.

According to Professor Gordon McFiggans, from Manchester University’s School of Earth, Atmospheric and Environmental Sciences, organic material from these sources is quite volatile and in warm conditions exists as a vapour.

Under moist, cooler conditions where clouds form, the molecules of pollution make large particles that act as seeds for cloud droplets.

“…the cooling effect on global climate of the increase in cloud seed effectiveness is at least as great as the previously found entire uncertainty in the effect of pollution on clouds”

The mechanism for producing these cloud droplets is the same as natural processes from forests. Professor McFiggans gives as an example the aroma of pine, a form of organic gas.

The droplets that give off the delightful smell later form the basis of clouds. The organic gas from pollution does not smell as good, but has the same effect in producing cloud droplets.

“We discovered that organic compounds, such as those formed from forest emissions or from vehicle exhausts, affect the number of droplets in a cloud and hence its brightness, so affecting climate”, he said.

“We developed a model and made predictions of a substantially enhanced number of cloud droplets from an atmospherically reasonable amount of organic gases.

“More cloud droplets lead to brighter cloud when viewed from above, reflecting more incoming sunlight.

“We did some calculations of the effects on climate and found that the cooling effect on global climate of the increase in cloud seed effectiveness is at least as great as the previously found entire uncertainty in the effect of pollution on clouds”,  Professor McFiggans said. – Climate News Network

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by Tim Radford

Hare undone by unshed summer coat

May 4, 2013 in Science

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Camouflage does work: A snowshoe hare in Canada Image: Ansgar Walk

Camouflage does work: A snowshoe hare in Canada
Image: Ansgar Walk

By Tim Radford

Species which protect themselves by turning white to match the snow of the long northern winters may be caught out as a warming climate reduces the numbers of days of snow cover.

LONDON, 4 May – Milder winters mean bad news for the snowshoe hare of western North America. Lepus americanus is famous for two things: an evolutionary camouflage adaptation that keeps it white in the winter snow and turns it a reddish brown in spring and summer; and its intimate population polka with one of the continent’s most glamorous predators, the Canada lynx.

When hares are numerous, the lynx population increases. As the numbers of hares diminish, so its predators go hungry and the lynx population starts to drop, giving the snowshoe hares another chance.

But the hare may be losing the battle, thanks to climate change. Biologists report in the Proceedings of the National Academy of Sciences that they monitored 148 wild hares in western Montana and observed that the adaptation that gave the hares an advantage in stable climates is likely to work to their disadvantage as temperatures rise, snow cover shrinks and the winters get shorter. The three years of their study included both the shortest and the longest snow seasons since 1970.

The researchers found that the spring and autumn moults seemed to occur independently of the arrival of the snows: they conjecture that they may be triggered by changes in daylight length.

Since hares don’t get much chance to die of old age – predation comprises 85 to 100% of mortality in different regions and different years – camouflage would play an important role in keeping hares alive long enough to breed and rear their young.

Poster child

 

A white hare on brown soil or a brown hare in the snow would both be at a serious disadvantage. Over the three-year period, the researchers had plenty of chances to observe both.

They expect “increased coat colour mismatch as snow seasons shorten under future climate change” and without rapid adaptation, this mismatch will increase as much as fourfold by mid-century and eightfold by the late century if humans go on pumping greenhouse gases into the atmosphere at an increasing rate.

The average annual duration of snow cover is forecast to fall by 29 to 35 days by mid-century and by 40 to 69 days by the end of the century.

Hares, the researchers warn, won’t be the only coat-changing mammals left exposed by ever-shorter winters. They conclude that there is a lot to learn from the plight of the hare (and see our story of 18 January)..

“The compelling image of a white animal on a brown snowless background can be a poster child for both educational outreach and for profound scientific inquiry into fitness consequences, mechanisms of seasonal coat colour change, and the potential for rapid local adaptation”, they say. – Climate News Network

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by Tim Radford

Superstorm Sandy set off seismometers

May 3, 2013 in Science

FOR IMMEDIATE RELEASE

A victim of Sandy: A replica of the British vessel HMS Bounty goes down Image: US Coast Guard

A victim of Sandy: A replica of the British vessel HMS Bounty goes down
Image: US Coast Guard

By Tim Radford

The energy released by 2012′s Superstorm Sandy in the US was so immense that it triggered seismic waves which registered on equipment designed to detect earthquakes.

LONDON, 3 May – Sandy, the superstorm that all but submerged New York, was powerful enough to set US earthquake detectors quivering long before it hit the American coastline.

It stirred up Atlantic Ocean waves that slammed into each other, started to shake the sea floor and then shook the Midwestern states so vigorously that the storm’s progress could be tracked by seismometer.

The windstorm-induced tremors were very tiny, and not unusual – and say as much about the sensitivity of modern seismometers as about the furious forces released in a superstorm.

But the episode – revealed at a recent meeting of the Seismological Society of America in Salt Lake City, Utah – is a reminder that the energies released by the dangerous mix of swirling winds and warm oceans are dramatic and, with global warming, could become even more frequent and more devastating.

“We detected seismic waves created by the ocean waves both hitting the East Coast and smashing into each other”, said Keith Koper, of the University of Utah seismic stations. And his colleague and fellow author of an as-yet-unpublished study, Oner Sufri, a doctoral student, said “As the storm turned west-northwest, the seismometers lit up.”

Sandy began in the Caribbean, developed into a hurricane – the largest Atlantic hurricane on record – and killed 285 people in seven countries, as well as causing an estimated $75 billion in damage. It hit 24 US states and swept into New York on 29 October, by then classified as a superstorm.

Biennial superstorms?

 

Hurricanes generate phenomenal energies. One calculation is that the total energy released through clouds and rain during the average hurricane is about 200 times the capacity of all the world’s power stations. Another more graphic calculation is that during its lifespan, the average hurricane releases the energy of 10,000 nuclear bombs.

Some of this marine mayhem was picked up by an array of 500 portable detectors called Earthscope. These were first placed in California in 2004, and have been leap-frogging eastwards across the US.

When Sandy developed, most of them were located in a band between Minnesota and east Texas, and Lake Erie and Florida. They were designed to tune in, a bit like a doctor’s stethoscope, to the Earth’s crust and the mantle below.

Sandy in effect helped geophysicists explore the fabric of the continental US – but the tiny tremors in the crust also told the researchers about the progress of a storm far away.

Hurricanes become a predictable hazard as ocean surface temperatures rise, and in 2012 seas off the east coast of the US were unusually warm.

Sandy was classified a very unusual event, a once-in-a-century storm, but researchers have warned that, as global temperatures rise, such storms could develop as often as every other year. – Climate News Network

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by Tim Radford

Warming trees limit warming – a little

May 1, 2013 in Science

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The Smoky Mountains live up to their name Image: John Phelan

The Smoky Mountains live up to their name
Image: John Phelan

By Tim Radford

Warmer temperature prompts trees to release aerosols which in turn stimulate cloud formation. And that can help to cool the temperature, at least modestly.

LONDON, 1 May – Trees may provide the Earth with a little shade from global warming – indirectly. European and Canadian researchers report that they have found what engineers like to call a negative feedback loop above the forests of Europe and North America.

It works like this. Trees – those natural chemical factories that routinely deliver complex aromatic compounds such as rubber, coffee, chocolate, resins, pungent fruits, oils and natural drugs such as quinines – are a permanent source of volatile organic compounds released into the atmosphere.

On a hot day, trees release even more conspicuous quantities of terpenes, isoprenes and other compounds into the air. These are wafted higher in the atmosphere and begin to mix, oxidise, or chemically react with other atmospheric gases, aerosols and car and factory exhausts to form increasingly larger particles on which water vapour might condense.

This is not a new observation. The Smoky Mountains of Tennessee and North Carolina take their name from the pall of isoprenes discharged from the oaks that cover the hills: the mountains actually look smoky.

The aerosols from trees float in the atmosphere and reflect and scatter sunlight and even form cloud droplets. So far, so familiar.

But Pauli Paasonen, of the University of Helsinki and the International Institute for Applied Systems Analysis in Laxenburg, Austria, writes in Nature Climate Change that he and 23 colleagues in Finland, Sweden, Germany, Canada and the US decided to assess the overall effect of these aerosols and their contribution to, or impact upon, global warming.

Every little helps

They analysed data from eleven measuring stations spread across the northern hemisphere, from semi-Arctic wilderness to polluted agricultural lands, and worked out how the quantities of cloud condensation nuclei might be linked to air temperatures.

They found a clear connection. The warmer the weather, the greater the likelihood that gas emissions from plants would create conditions for the formation of clouds, which in turn would reflect more sunlight back into space, and thus help damp down global warming.

That is the good news. The not-so-good news is that these plant gas emissions won’t make a great deal of difference – on a global scale they might counter about 1% of global warming.

On a regional scale, however, the effect might be much greater: in heavily forested areas – Finland, Siberia and Canada, for instance – where human emissions of aerosols are anyway relatively slight, plant gas releases might counter as much as 30% of warming.

The effect however was not easy to predict, and may not be easy to confirm. The key variable is the boundary layer of the atmosphere at which gases and particles mix and form the nuclei around which cloud droplets might condense, and the height of this boundary changes with weather conditions.

“Plants, by reacting to changes in temperature, also moderate these changes”, says Dr Paasonen. “One of the reasons that this phenomenon was not discovered earlier was because these estimates for boundary layer height are very difficult to do.” – Climate News Network

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by Tim Radford

Fast-moving climate zones speed extinction

April 26, 2013 in Science

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Heading for extinction? Rising temperatures are heightening the risk Image: Dick Mudde

Heading for extinction? Rising temperatures are heightening the risk
Image: Dick Mudde

By Tim Radford

An increasingly warm climate will mean ever more rapid changes in the Earth’s climatic zones, researchers say, and the species that live there will face a heightened extinction risk.

LONDON, 26 April – As global temperatures rise, climate zones will shift at greater speed, according to new research in Nature Climate Change.

If greenhouse gas emissions carry on increasing, then about 20% of the land area of the planet will undergo change – and the creatures that have made their homes in what were once stable ecosystems will have to adapt swiftly, or face grim consequences.

“The warmer the climate gets, the faster the climate zones are shifting”, says Irina Mahlstein, of the US NOAA Earth System Research Laboratory in Boulder, Colorado. “This could make it harder for plants and animals to adjust.”

Such fears are not new: in the past two decades biologists and ecologists have repeatedly warned that vulnerable species were at risk from climate change.

But vulnerable species are at risk anyway, just from pollution, habitat destruction and the spread of humanity across the habitable globe. What Dr Mahlstein and her colleagues have done is to look at geography’s mosaic of climates and landscapes and measure the rates of change in these.

Late in the 19th century, European geographers began to map and define – and create labels for – climatic regions: the hot arid regions, the tundra, the tropical rainforests, the steppes, monsoon climates, Mediterranean climates and so on.

“…species will have increasingly less time to adapt to zone changes, which is expected to increase the risk of extinction”

The idea was to be able to predict the life that might make its home in such places, according to temperature, precipitation and seasonal cycles. This Köppen-Geiger climate classification became a handy base for considering what might happen as the world gets hotter.

Mahlstein and her colleagues considered what might happen over a two century stretch: from 1900 to 2098, under climate model simulations based on scenarios for warming.

They found that with a warming of 2°C, about 5% of land would shift into a new climate zone. As the temperatures rise another 2°C, 10% of the land area shifts to a new zone.

Temperate regions and the high latitudes will experience the most dramatic change, and in the tropics, the mountain regions will experience greater change than the lowlands.

Frost climates will begin to shrink; arid zones will increase, and regions that once experienced cool summers will find that things get hotter.

“About 20% of all land area undergoes a change in its original climate,” say the researchers. “This implies that species will have increasingly less time to adapt to Köppen zone changes in the future, which is expected to increase the risk of extinction.” – Climate News Network

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by Tim Radford

Black carbon flows from soil to seas

April 25, 2013 in Science

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Charcoal and black carbon do not stay where they are put, and much ends in the oceans Image: Juliancolton

Charcoal and black carbon do not stay where they are put, and much ends in the oceans
Image: Juliancolton

By Tim Radford

Charcoal and other forms of black carbon do not, as previously thought, stay where they are buried: they migrate to the oceans and recirculate the carbon they contain.

LONDON, 25 April – Climate scientists may have to rethink some of their old assumptions about carbon. US and European researchers have just established that black carbon, soot and biochar – the burnt remains from countless forest fires -  doesn’t stay in the soil indefinitely.

Around 27 million tons of the stuff gets dissolved in water and washed down the rivers into the oceans each year.

Black carbon or biochar has been hailed as one possible way of limiting greenhouse gas emissions, by taking carbon out of circulation. But this study, according to a report in the journal Science, “closes a major gap in the global charcoal budget and provides critical information in the context of geo-engineering”.

Forest, bush, scrub and peat fires produce somewhere between 40 and 250 million tons of black carbon every year. Had this burning been complete, this would have ended up as carbon dioxide, back in the atmosphere.

So researchers have counted the biochar locked in the soil – where it enhances fertility – as carbon out of circulation for millions of years. But analysis of water from the world’s 10 largest rivers – the Amazon, the Yangtse, the Congo and so on – told a different story.

“Each sample included a significant amount of black carbon”, said Anssi Vähätalo, now of the University of Jyväskylä in Finland. “On average, the amount of black carbon was 10% of the amount of dissolved organic carbon.

“The results prove that the proportion of water-soluble carbon may be as much as 40% of black carbon created annually.”

The sampled rivers carry one third of the water running to the oceans, from a catchment area that embraces 28% of the planet’s land area.

More CO2 released

 

The research is yet another step in the long and tricky international effort to understand just how the world works: how life’s raw materials are consumed, exploited and recycled, and why greenhouse gas emissions are stubbornly on the increase.

Fossil fuel burning puts back into the atmosphere the carbon dioxide – and the warmth – locked away in the Carboniferous period and buried for 300 million years.

Log fires simply restore carbon dioxide to the atmosphere that was locked up a few decades earlier, in the growing tree: log fires in that sense are carbon neutral, or even carbon negative, since a lot of the carbon lingers and is buried as ash, soot or charcoal.

Some environmentalists have argued that greater use of biochar could slow and perhaps ultimately reduce global warming by taking carbon out of circulation. The accounting may not be so simple.

“Most scientists thought charcoal was resistant. They thought, once it is incorporated in the soils, it would stay there,” said Rudolf Jaffé from Florida University.

“When charcoal forms it is typically deposited in the soil. From a chemical perspective, no one really thought it dissolves, but it does.

“It doesn’t accumulate, like we had for a long time believed. Rather, it is transported into wetlands and rivers, eventually making its way into the oceans.” – Climate News Network

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