Plants to offer minor dimming effect as climate warms: Nature

The Age, April 30, 2013  

Plants help to slow climate change by emitting gases as temperatures rise that lead to the formation of a sunshade of clouds over the planet, scientists said on Sunday.

The tiny sun-dimming effect could offset about one per cent of warming worldwide and up to 30 per cent locally such as over vast northern forests in Siberia, Canada or the Nordic nations, they wrote in the journal Nature Geoscience.

While proportionally small, some scientists said the study provided further evidence of the importance of protecting forests, which help to slow climate change by absorbing greenhouse gases as they grow and to preserve wildlife.

Observations of forests from 11 sites around the world showed that plants emitted tiny particles that float on the wind as temperatures warm and act as seeds for water droplets that create clouds, they wrote.

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Clouds' white tops in turn reflect sunlight back into space and offset warming, they wrote.

The study focused on forests in Europe, North America, Russia and southern Africa. The effect is believed to be smaller over far hotter tropical forests such as in the Amazon or the Congo basin.

"It's a small effect - one per cent is not much," said lead author Pauli Paasonen of the University of Helsinki and the International Institute for Applied Systems Analysis in Austria.

"If temperatures were to increase by 1 degree without this effect, they'd rise 0.99 degrees with it," he told Reuters of a study that included researchers in the United States, Canada, Germany, the Netherlands, South Africa, Hungary and Sweden.

Sunshade

Many other tiny aerosols, such as human pollution from factories, cars and power plants, also have a sun-dimming effect that may be slowing the pace of climate change, blamed mainly on emissions of greenhouse gases such as carbon dioxide.

But there has been uncertainty about the role of nature, and of plants' emissions of gases such as monoterpenes.

"Everyone knows the scent of the forest," Ari Asmi, a University of Helsinki researcher who also worked on the study, said in a statement. "That scent is made up of these gases."

It is unclear why plants emit more monoterpenes at higher temperatures - it may be a side-effect of trees' natural air conditioning to reduce heat.

"Forests are providing an additional cooling. This is another reason why we should conserve and protect forests," said Dominick Spracklen, an expert on plants and climate change at the University of Leeds who was not involved in the study.

But the damaging effects of warming on forests, such as more wildfires or insect pests, may exceed tiny benefits of more clouds that would only come from healthy forests, he said.

Spracklen said plants' cooling effect was tantalising evidence for people who believe the planet somehow acts as a self-regulating organism for life, sometimes known as the Gaia hypothesis.

One idea launched in 1987 was that warmer temperatures spur the growth of more algae in the upper oceans. These tiny plants would in turn release more of the chemical dimethyl sulphide that seeds clouds to reflect sunlight.

"No one has yet proved that this effect exists," he said.

The U.N. panel of leading climate scientists says that human emissions of greenhouse gases are driving up world temperatures and will lead to ever more floods, droughts, heatwaves and rising sea levels.

It says that it is at least 90 per cent certain that human activities, rather than natural variations in the climate, are to blame for most of the warming in the past half-century.

(For the study: http://www.nature.com/doifinder/10.1038/ngeo1800)

Reuters

Coal producers ignore policy on carbon

Tom Arup   

The Age, April 29, 2013 

Companies are sitting on Australian coal resources likely to generate an extra 150 billion tonnes of greenhouse gases, setting a potential collision course with international efforts to curb global warming that would strand investments.

A new report claims investments in new Australian coal, oil, and gas projects are being made with no regard for the risk that they will later be devalued as the world moves to cut emissions.

The report by the British-based Carbon Tracker Initiative and the Australian Climate Institute says companies listed on the ASX 200 spend $5.7 billion a year developing and replacing coal reserves.

It says these reserves will largely have to be left unburnt if global warming is to be kept at safe levels.

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Climate Institute chief executive John Connor said investments in Australian coal rest on a speculative bubble of climate denial, indifference or dreaming.

"Investors, governments and even some coal companies, say they take climate change seriously, but this report shows they do not or are taking risky gambles," he said.

The report studies Australian coal reserves and resources that companies have on their books and calculates the potential emissions that would emerge if developed.

It finds Australian companies hold coal resources that would generate 115 billion tonnes of greenhouse gases. When Australian coal resources owned by foreign listed companies are added, it brings the total emissions potential to about 300 billion tonnes.

But the report authors say international assessment standards recognise that only about 50 per cent of these resources will be developed.

If developed, the resources would double Australia's proven listed coal reserves, and the associated 150 billion tonnes of emissions would equate to 300 times Australia total annual emissions in 2012.

The extra greenhouse gases from Australian coal alone would account for 75 per cent of the total amount of global emissions that can come from burning coal to give the world a strong chance of keeping global warming to two degrees – the international target agreed by countries through the United Nations.

The report says this would be a vast proportion of the global carbon budget to be given to a single country, "especially true given that Australia produces only 11 per cent of the total global coal production".

The report warns Australia is also exposed to efforts by its major coal customers to improve their energy efficiency and reduce their emissions. In particular the researchers point to China's target to cap coal use at four billion tonnes by 2015.

"investors need to challenge the assumption that coal demand will continue to rise in China and elsewhere, otherwise billions of dollars of taxpayer, superannuation and shareholder funds will be wasted in assets linked to unburnable carbon," Carbon Tracker's research director, James Leaton, said.

The report follows a global assessment by Carbon Tracker and the Grantham Institute finding hundreds of billions of dollars in fossil fuel projects would be stranded, triggering a potential economic crisis, if companies continue to invest in carbon-intensive projects while governments introduce stronger policies to limit global warming.

Greenhouse gas levels highest in 3m years

Ben Cubby, Environment Editor  

The Age, April 29, 2013

Carbon dioxide concentrations in the Earth's atmosphere are on the cusp of reaching 400 parts per million for the first time in 3 million years.

The daily CO2 level, measured at the Mauna Loa Observatory in Hawaii, was 399.72 parts per million last Thursday, and a few hourly readings had risen to more than 400 parts per million.

''I wish it weren't true but it looks like the world is going to blow through the 400 ppm level without losing a beat,'' said Ralph Keeling, a geologist with the Scripps Institution of Oceanography in the US, which operates the Hawaiian observatory.

''At this pace we'll hit 450 ppm within a few decades.''

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The 450 ppm level is considered to be the point at which the world has a 50 per cent chance of avoiding dangerous climate change. Any higher and the odds of avoiding searing temperature rises of 4 or 5 degrees by the end of the century become prohibitively risky.

The rise in greenhouse gases corresponds with the extra amount of CO2 known to have been emitted by human activities, such as burning fossil fuels and cutting down forests. More greenhouse gases means more heat builds up at the Earth's surface.

The last time CO2 reached the symbolic milestone of 400 parts per million in the atmosphere - in the Pliocene era - temperatures rose by between 3 and 4 degrees and sea levels were between five and 40 metres higher than today. Carbon dioxide levels have been rising steadily since constant measurements began at the Hawaiian observatory in 1958, when the level was about 317 parts per million.

Levels of more than 400 parts per million have been recorded at a few polar monitoring stages in the past year but the Mauna Loa Observatory readings are considered the most definitive.

Climate Commission releases new report

The finding comes as Australia's Climate Commission was set to issue a new report into global action to reduce emissions.

The US and, particularly, China are starting to move into leadership positions on greenhouse gas reductions, the report, titled The Critical Decade: Global Action Building on Climate Change, says.

The rise in coal use in China had slowed substantially and renewable energy had expanded on a massive scale, the report said. Wind power generation in China had increased almost 50-fold between 2005 and 2012, and new solar power capacity had risen by 75 per cent last year and was expected to triple by 2015.

Australia had doubled its renewable energy capacity between 2001 and 2012 but was at some risk of being left behind by other nations, Climate Commission chief commissioner Tim Flannery said.

"There are a lot of opportunities for Australia but the world is changing quickly and we need to be prepared,'' Professor Flannery said. ''We are the 15th largest emitter in the world, larger than 180 other countries. We are more influential than most of us think."

New study: Pace of climate zone shifts quickens as climate warms

NOAA April 22, 2013

As our planet is warming, not only have Earth's climate zones begun to shift – they will actually continue to shift at an accelerating pace, according to a new study led by a scientist at the NOAA Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado. This acceleration of change means that the species inhabiting each zone have less time to adapt to the climatic changes.   

"The warmer climate gets, the faster the climate zones are shifting. This could make it harder for plants and animals to adjust," said lead author Irina Mahlstein, a CIRES scientist who is located at the NOAA Earth System Research Laboratory in Boulder, Colo. A paper by Mahlstein and collaborators at NOAA and the Massachusetts Institute of Technology is now online in the journal Nature Climate Change   

 The study is the first to look at the accelerating pace of the shifting of climate zones. For this study, the scientists used a climate zone classification system known as the Koppen-Geiger classification, which defines areas of the Earth by annual and seasonal cycles of temperature and precipitation, as well as temperature and precipitation thresholds of plant species. This system identifies more than 30 different climate zones. Examples include the equatorial monsoonal zone, the polar tundra zone and cold arid desert zone.   

"A shift in the climate zone is probably a better measure of 'reality' for living systems, more so than changing temperature by a degree or precipitation by a centimeter," said Mahlstein.   

The scientists used climate model simulations to look at the shifts between Koppen-Geiger climate zones over a two-century period, 1900 to 2098. The team found that for the initial two degrees Celsius of warming, about 5 percent of Earth's land area shifts to a new climate zone. The models show that the pace of change quickens for the next two degrees of warming, and an additional 10 percent of the land area shifts to a new climate zone.   

Certain regions of the globe, such as North America, Europe and others at the middle and high latitudes of the globe, will undergo more changes than other regions, such as the tropics, the scientists found. In the tropics, mountainous regions will experience bigger changes than their surrounding low-altitude areas.   

In the coming century, the findings suggest that frost climates — the coldest climate zone of the planet — are largely decreasing. Generally, dry regions in different areas of the globe are increasing, and a large fraction of land area is changing from cool summers to hot summers.     

The scientists also investigated whether temperature or precipitation made the greater impact on how much of the land area  changed zones. "We found that temperature is the main factor, at least through the end of this century," said Mahlstein.    John Daniel at the NOAA Earth System Research Laboratory and Susan Solomon at the Massachusetts Institute of Technology coauthored the study.  

NOAA's mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. 

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20th century 'hottest in 1400 years'

Tom Arup, Environment editor

The Age, Date April 22, 2013 

Warming over the 20th century produced the hottest global average temperatures in 1400 years, a major scientific research project has found.

In a paper published in the journal Nature Geoscience on 21 April, an international team of scientists reconstructed temperatures over the past 2000 years using proxy records such as tree-ring measurements, pollen sampling, coral reefs, ice cores and historical records.

The study found that the global warming that began in the late-19th century reversed a long cooling trend across the planet that lasted well over 1000 years.

One of the authors of the paper, Dr Steven Phipps from the University of NSW's ARC Centre of Excellence for Climate System Science, said: "The striking feature about the sudden rise in 20th century global average temperature is that it comes after an overall cooling trend that lasted more than a millennium.

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"This research shows that in just a century the Earth has reversed 1400 years of cooling."

When the reconstructed temperatures are averaged across the planet, the best estimate of past temperatures finds 1971–2000 was warmer than any other time in nearly 1400 years.

But some of the seven different regions studied may have experienced similar or warmer temperatures at other times.

The paper says the findings do not consider uncertainty associated with the temperature estimates, and the reconstruction for each area covered different periods within the 2000 years, depending on the availability of data.

In Australia and Asia, the reconstructed temperature was highest during 1971–2000 than at any other period over the studied timelines.

The paper says the millennium-long cooling trend – and earlier warmer temperatures – were primarily driven by natural cycles in the Earth's orbit and some volcano and solar activity. But natural influences do not account for the dramatic global temperature rises of the 20th century, the report says.

Rising greenhouse gas emissions are attributed to human activity, mainly from the burning of fossil fuels and, while the recent warming is a global trend, other temperature anomaly periods – such as the Mediaeval Warm Period and the Little Ice Age – occurred only regionally.

Professor Jonathan Overpeck, visiting fellow of the Victorian Centre for Climate Change Adaptation Research, said it confirmed that recent global and continental-scale warming was "very unusual" in recent Earth history and was driven mostly by human emissions of greenhouse gases.

Climate change's role in big Antarctic melt

Two different areas of Antarctica tell two very different stories about how climate change might be affecting ice melt. The data appear to confirm that climate change impacts can be very local.

By Pete Spotts, Staff writer / April 16, 2013

The Christian Science Monitor

For more detail read "Ice Hockey" - Eric Steig, Real Climate

Since the early 1990s, glaciers draining Antarctica's vast ice sheets have dumped ice into the ocean at an an eye-popping rate.

Now, two new studies of ice cores from different parts of the continent are yielding important clues as to why the loss rates have been so high.

On the Antarctic Peninsula, global warming appears to be taking a direct toll. Glaciers are melting mainly from the top down. The peninsula is losing land ice in the summer at a rate unmatched in the past 1,000 years.

For the West Antarctic Ice Sheet, one of two vast continental sheets, losses also have been relatively large. There, however, floating ice shelves that form the seaward end of glaciers are melting from the bottom up. Today's losses are comparable to those that have occurred a few other times over the past 2,000 years. The authors say that for now, the evidence points to the extended reach of naturally shifting climate patterns in the tropical Pacific as driving the losses.

At first blush, the two might appear to be at loggerheads. Instead, researchers suggest, the two highlight how, as on other continents, the intensity of global warming's impact at the bottom of the world depends on location, location, location. And both point to the challenge researchers still face in forecasting the future of the continent's ice chest in a warming climate.

Each in its own way "provides guidance on projecting the future of sea-level rise," notes Richard Alley, a glaciologist at Penn State University in University Park, Pa., who was not a participant in either study.

Researchers have a keen interest in trying to understand and project ice losses in Antarctica, as well as on Greenland, with global warming. Previous studies have shown that since 1992, the loss of ice from polar caps is raising sea levels by an average of about 0.59 millimeters a year.

The West Antarctic Ice Sheet alone could boost sea levels an average of 10 feet if it melts – an increase that would occur over hundreds to thousands of years, notes Eric Steig, a researcher at the University of Washington who led one of the two research efforts.

Between 1992 and 2011, the peninsula lost ice at rate of 20 billion tons a year, according to a study published last November in the journal Science. The West Antarctic Ice Sheet lost 65 billion tons a year, and the East Antarctic Ice Sheet – the continent's largest – lost 14 billion tons a year, although the uncertainties in that number are so large the loss could just as well have been nothing.

Antarctic Peninsula

The Antarctic Peninsula is an extended arm of land that last shook hands with the southern tip ofSouth America roughly 235 million years ago when the two continents drifted apart. It's mountainous and extends into the Southern Ocean to some 250 miles above the Antarctic Circle.

"In some ways, it's a climate oddity," writes Robert Mulvaney, a researcher with the British Antarctic Survey (BAS) and a member of the team formally reporting its results on the region's ice Sunday in the journal Nature Geoscience, in an e-mail. Relatively warm westerly winds, laden with with ocean moisture, blow across the peninsula. So it tends to be warmer than the mainland and experiences higher snowfall rates.

Even so, the buildup of the loss of ozone in the stratosphere and the buildup of greenhouse gases – both from human industrial activity – have affected circulation patterns over the region in ways that have left the peninsula as one of the fastest-warming regions on the planet.

The BAS team, led by Nerilie Abram a researcher with the Australian National University and the BAS, analyzed portions of a 1,194-foot-long ice core from a glacier on James Ross Island.

They found that from the coldest point in their record, between 1410 and 1460, melt rates are about 10 times higher today than they were then. But most the most intense melting has occurred since the middle of the last century. And it's been occurring at the surface, providing water that can lubricate the bottom of land glaciers and filling crevasses to act as ice-breaking wedges when the trapped water refreezes.

The results show that "the Antarctic Peninsula has warmed to a level where even small increases in temperature can now lead to a big increase in summer ice melt," said Dr. Abram in a prepared statement.

West Antarctic Ice Sheet

Meanwhile, Dr. Steig's team analyzed an ice core from high on the West Antarctic Ice Sheet, some 350 miles inland from the Amundsen Sea – comparable to the distance between Los Angeles; and Flagstaff, Ariz. The core covers 2,000 years of climate history. In addition, the team used data from other cores taken in the region and found that its core does a good job of representing conditions in the region as a whole.

In general, the climate on the ice sheet is significantly different, notes Steig. It lacks the warmer temperatures that accompany an oceanfront view. And the surface at the drill sites is around 6,000 feet above sea level. When the sheet loses ice, it's at the ocean end of glaciers that typically become grounded on the sea floor. But changing wind patterns can bring to the surface warm water that usually stays deeper in the ocean. This warm water melts the shelves from underneath until they no longer are grounded. The ungrounded portions break free as vast icebergs, leaving the glacier to deliver more interior ice to the coast, where the process repeats.

As the BAS team found, Steig and colleagues noted warming during the 1990s, accelerating the ice loss. But the team also found that comparable conditions in the 1830s and 1940s, as well as further back. That suggests a loss of ice comparable to the rates seen today, he and his colleagues say.

The '90s, '40s, and 1830s were characterized by strong El Niños – conditions in the tropical Pacific in which waters in the eastern tropical Pacific are warmer than normal, while the waters in the western Pacific are cooler than normal. This alters atmospheric circulation patterns. While the effects are strongest in the tropics, they appear at higher latitudes as well.

Thus, at least for now, it would appear that natural climate swings are playing a greater role in the loss of ice from West Antarctica than global warming, the researchers suggest.

If conditions are largely governed by conditions in the tropical Pacific, as they appear to be, an ability to project the ice sheet's future in a warmer world depends on researcher's ability to figure out whether El Niño conditions will predominate in the future, or La Niña conditions – El Niño's opposite. This study also was published Sunday in Nature Geoscience.