Canadian Study Sees Global Warming For Centuries

Jeffrey Jones PlanetArk 10 Jan 11;

Carbon dioxide already emitted into the atmosphere will keep contributing to global warming for centuries, eventually causing a huge Antarctic ice sheet to collapse and lift sea levels, Canadian scientists said on Sunday.

Even the complete abandonment of fossil fuels and halt to emissions cannot prevent devastating ocean warming in Antarctica as well as increasing desertification in North Africa, the research finds.

Even so, many of the negative consequences in the Northern Hemisphere, such as loss of Arctic sea ice, are reversible. That means global efforts to cut greenhouse gases are not a waste of effort and money, said Shawn Marshall, a University of Calgary geography professor and one of the study's authors.

"But there are some parts of the climate that have a lot of inertia and it will take many centuries before they start to reverse," said Marshall.

The study, led by Nathan Gillett of the Canadian Center for Climate Modeling and Analysis, is published in the journal Nature Geoscience.

Using simulations with a climate model, the scientists estimated the effects on climate patterns for the next 1,000 years by stopping emissions completely in 2010 and in 2100.

Major differences of the impacts in various regions lie in the centuries it takes for heat to circulate from the North Atlantic through the world's ocean currents and into the deep sea, Marshall said.

"The atmosphere cools pretty quickly when atmospheric gases go down and surface water will cool, but that doesn't reach the deeper waters of the ocean for a long time," he said.

Wind currents in the southern hemisphere may also play a role.

As a result, in the next 1,000 years, the average ocean temperature around Antarctica could rise by as much as 5 degrees Celsius, triggering the collapse of the West Antarctic ice sheet, according to the study.

The elimination of the ice sheet, which covers an area about the size of Texas and is up to 4,000 meters (13,120 feet) thick, could raise sea levels by several meters.

The climate impacts would also dry out the land in parts of North Africa by up to 30 percent.

Simulations show big differences in some parts of the world, however, between cutting emissions in 2010 and in 2100, including long-term temperature variations between 1 and 4 degrees Celsius, an argument for action on carbon dioxide, Marshall said.

"You sometimes hear that defeatist argument that it's too late and there are a lot of changes that are going to happen, so just worry about adaptation," he said. "But I think you do see a big divergence in potential futures depending on if there are some reductions in emissions."

(Editing by Frank McGurty)

Glacier shrinkage will hit European Alps hardest, study claims
Global warming research warns of rising sea levels and threat to water supplies
Sylvia Rowley guardian.co.uk 9 Jan 11;

Glaciers in the European Alps could shrink by 75% by the end of the century, according to new research into the expected impact of global warming.

The study, published in the journal Nature: Geoscience, concludes that, globally, mountain glaciers and ice caps are projected to lose 15-27% of their volume by 2100, although the extent of the damage varies widely. The analysis suggests glaciers in the Alps and New Zealand will shrink by more than 70% but shrinkage is predicted to reach about 10% in Greenland and high-mountain Asia.

The researchers argue this will result in "substantial impacts" on regional water availability, as well as a rise in sea levels. Retreating glaciers and ice caps threaten the water supplies of cities such as Kathmandu in Nepal and La Paz in Bolivia, which depend substantially on glacial meltwater for drinking and farming.

Scientists from the University of British Columbia in Vancouver, Canada, who conducted the research, predict that melting glaciers and ice caps will be responsible for increases in sea levels of 8.7-16.1cm by 2100. This broadly confirms the range projected by the UN's climate change body, the Intergovernmental Panel for Climate Change (IPCC).

"What is surprising here is the contribution to sea level rises of up to 16cm just from the melting of small glaciers and ice caps. This may still be a low estimate as we did not include ice loss from calving – when a piece of ice breaks off into the sea," said Dr Valentina Radic, who co-authored the study with Prof Regine Hock.

Total sea level rise is likely to be considerably higher, however, due to the effects of melting Greenland and Antarctic ice sheets – which make up more than 99% of the water on Earth bound up in glacier ice – and thermal expansion in the ocean.

Dr Murray Simpson, senior research associate at Oxford University's Centre for the Environment, said: "All studies since 2007 clearly show that, in total, sea levels will rise 1-2 metres by the end of the century."

Radic and Hock arrived at the figures by simulating the response of 2,638 ice caps and 120,229 mountain glaciers worldwide to the changes in climate projected by 10 state-of-the-art climate models. These models were developed for the last IPCC report, including models produced by Nasa and the UK Met Office.

The research found that melting mountain glaciers and ice caps have made a growing contribution to sea level rise over past decades. While mountain glaciers and ice caps include only a minor fraction of all water on Earth bound in glacier ice (less than 1%), their retreat has caused half of sea level rises from melting ice over the past 50 years.

"Small glaciers and ice caps will be an important and increasing contributor to sea level rises this century," said Radic.

Warming to devastate glaciers, Antarctic icesheet - studies
Yahoo News 9 Jan 11;

PARIS (AFP) – Global warming may wipe out three-quarters of Europe's alpine glaciers by 2100 and hike sea levels by four metres (13 feet) by the year 3000 through melting the West Antarctic icesheet, two studies published on Sunday said.

The research places the spotlight on two of the least understood aspects of climate change: how, when and where warming will affect glaciers on which many millions depend for their water, and the problems faced by generations in the far distant future.

The glacier study predicts that mountain glaciers and icecaps will shrink by 15-27 percent in volume terms on average by 2100.

"Ice loss on such a scale may have substantial impacts on regional hydrology and water availability," it warns.

Some regions will be far worse hit than others because of the altitude of their glaciers, the nature of the terrain and their susceptibility to localised warming.

New Zealand could lose 72 percent (between 65 and 79 percent) of its glaciers, and Europe's Alps 75 percent, meaning a range of between 60 and 90 percent. At the other end of the scale, glacial loss in Greenland is predicted at around eight percent and at some 10 percent in high-mountain Asia.

Meltwater will drive up world sea levels by an average of 12 centimetres (five inches) by 2100, says the study.

This figure -- which does not include expansion by the oceans as they warm -- largely tallies with an estimate in the landmark Fourth Assessment Report by the UN's Intergovernmental Panel on Climate Change (IPCC) in 2007.

Geophysicists Valentina Radic and Regine Hock of the University of Alaska base these calculations on a computer model derived from records for more than 300 glaciers between 1961 and 2004.

The model factors in the middle-of-the-road "A1B" scenario for greenhouse-gas emissions, by which Earth's mean surface temperature would rise by 2.8 degrees Celsius (5.04 degrees Fahrenheit) during the 21st century.

The tool was then applied to 19 regions that contain all the world's glaciers and icecaps.

But -- importantly -- it does not include the icesheets of Antarctica and Greenland, where 99 percent of Earth's fresh water is locked up.

If either of these icesheets were to melt significantly, sea levels could rise by an order of metres (many feet), drowning coastal cities.

That very scenario emerges in the second study, which focuses on the inertial effect of greenhouse gases. Carbon molecules emitted by fossil fuels and deforestation linger for many centuries in the atmosphere before breaking apart.

Even if all these emissions were stopped by 2100, the warming machine would continue to function for centuries to come, says the investigation.

It largely bases its forecast on the "A2" emissions scenario, which sees greater carbon pollution by 2100, stoking Earth's temperature by an average 3.4 C (6.1 F) by century's end.

Warming of the middle depths of the Southern Ocean could unleash the "widespread collapse" of the West Antarctic icesheet by the year 3000, it says.

"The inertia in intermediate and deep ocean currents driving into the southern Atlantic means those oceans are only now beginning to warm as a result of CO2 (carbon dioxide) emissions from the last century," said Shawn Marshall, a professor the University of Calgary in Canada.

"The simulation showed that warming will continue, rather than stop or reverse, on the thousand-year timescale."

The two studies are published online by the journal Nature Geoscience.