18/3/12

Is there enough time to prevent widespread thawing of permafrost?

This Q&A is part of the Guardian's ultimate climate change FAQ

• See all questions and answers
• Read about the project


Postdam Institute and Duncan Clark
 Guardian.co.uk, Wednesday 14 March 2012-03-18


'Drunken forests' in Fairbanks, Alaska, caused by the permafrost melting beneath the trees. Photograph: Ashley Cooper/Corbis 

As we've noted in this series, scientists are concerned that global warming could cause much of the world's permafrost (deep-frozen soils) to thaw, releasing vast quantities of greenhouse gases that would accelerate climate change – an example of a positive feedback loop.
Measurements have shown that southerly permafrost regions have already started to thaw and some additional thawing is unavoidable. Even if all man-made emissions ceased today, an additional global warming of about 0.6C would be expected due to the inertia of the climate system. Furthermore, due to polar amplification, man-made warming affects permafrost regions disproportionately: they warm around 50% more than the globe as a whole.
However, according to recent modeling work, if global emissions are cut rapidly and deeply enough to meet the world's stated target of limiting the average global temperature rise to 2C above pre-industrial levels, the majority of the world's permafrost will remain frozen.
By contrast, in a scenario without polities to reduce emissions, future warming is very likely to lead to a widespread disintegration of permafrost by the end of this century. In this scenario, the Arctic, which currently is an overall carbon sink, is expected to turn into a carbon source, because the carbon uptake from Arctic vegetation will be smaller than the release of carbon from thawing permafrost soils. The loss of permafrost carbon to the atmosphere would be irreversible on a human timescale and would mean that larger reductions in man-made emissions would be needed to achieve any target for CO2 concentration or global temperature rise.
• This article was written by Thomas Schneider von Deimling at thePotsdam Institute for Climate Impact Research in conjunction with the Guardian and partners

15/3/12

Met Office: Arctic sea-ice loss linked to colder, drier UK winters

This satellite image shows the minimum concentration of Arctic sea ice in 2005, when the sea ice extent dropped to 2.05m sq miles, the lowest recorded. The yellow outline indicates where the concentration of ice was as of September 1979. Photograph: NASA/AFP/Getty Images

Adam Vaugham

guardian.co.uk

The reduction in Arctic sea ice caused by climate change is playing a  role in the UK's recent colder and drier winter weather, according to theMet Office.

Speaking to MPs on the influential environmental audit committee about the state of the warming Arctic, Julia Slingo, the chief scientist at the Met Office, said that decreasing amounts of ice in the far north was contributing to colder winters in the UK and northern Europe as well as todrought. But she stressed that while it was one factor and not the "dominant driver" in the UK.
The south-east and other parts of England are experiencing especially dry conditions after months of below-average rainfall, with some water companies pledging on Monday to introduce hosepipe bans to conserve water.
Recent years have seen a spate of cold winters, with 2009-10 being recorded as the coldest in 31 yearsRecent studies have linked the gradual shrinking of Arctic sea ice to colder weather in the UK and the rest of Europe, as well as the US and China. However the Met Office has not spoken about the issue before. The hot, dry spring of 2011 has also been linked to melting sea ice by meteorologists.
Despite the colder winters, nine of the 10 hottest years on record have occurred since 2001, according to the Met Office's temperature data. Such warming, driven to largely by man-made activities, is causing Arctic sea ice to melt at a rate of 12% a decade in summer.
Slingo told the MPs that there is "increasing evidence in the last few months of that depletion of ice, in particular in the Bering and Kara seas, can plausibly impact on our winter weather and lead to colder winters over northern Europe".
She added that more cold winters mean less water, and could exacerbate future droughts. "The replenishment of aquifers generally happens in winter and spring … a wet summer does not replenish aquifers. So we are concerned if we have a sequence of cold winters that could be much more damaging," she told the committee.
Last month the environment secretary, Caroline Spelman, warned farmers that drought might become "the new normal" for the UK, because of climate change.
Slingo also dismissed fears that the Arctic could be entirely free of sea ice in summer as soon as 2015. Between 2025 and 2030 would be the earliest date she would consider it possible, she said, and the Met Office's latest models suggested 2040-60 as most likely. "Our expectation is certainly not in the next few years as you've heard from some evidence," she said.
She also said that suggestions the volume of sea ice had already declined by 75% already were not credible. "We know there is something [happening on the thinning of sea ice] but it's not as dramatic as those numbers suggest."
The problem, she explained, was that researchers did not know the thickness of Arctic sea ice with any confidence. She hoped a new ice-monitoring satellite launched in 2010, Cryosat2, would help with more accurate measurements.


2/3/12

How are Global Warming and the Gulf Stream Connected?

About.com-Environmental Issues


If melting glaciers deflect warm Gulf Stream, U.S. and Europe may freeze
From Larry West, former About.com Guide
Dear EarthTalk: What is the issue with the Gulf Stream in relation to global warming? Could it really stop or disappear altogether? If so, what are the ramifications of this? 

Lynn Eytel, Clark Summit, PAPart of the Ocean Conveyor Belt—a great river of ocean water that traverses the saltwater sections of the globe—the Gulf Stream stretches from the Gulf of Mexico up the eastern seaboard of the United States, where it splits, one stream heading for Canada’s Atlantic coast and the other for northern Europe and Greenland. By taking warm water from the equatorial Pacific Ocean and carrying it into the colder North Atlantic, the Gulf Stream warms up the eastern United States and northwestern Europe by about five degrees Celsius (roughly nine degrees Fahrenheit), making those regions much more hospitable than they would be otherwise.
Melting Glaciers Could Disrupt Warm Gulf Stream Currents

Among the greatest fears scientists have about global warming is that it will cause the massive ice fields of Greenland and other locales at the northern end of the Gulf Stream to melt rapidly, sending surges of cold water into the ocean system and interrupting the flow of the Ocean Conveyor Belt. One doomsday scenario is that such an event would stop or disrupt the whole Ocean Conveyor Belt system, plunging
Western Europe into a new ice age without the benefit of the warmth delivered by the Gulf Stream.
Gulf Stream May Affect Climate Change Worldwide

“The possibility exists that a disruption of the Atlantic currents might have implications far beyond a colder northwest
Europe, perhaps bringing dramatic climatic changes to the entire planet,” says Bill McGuire, a geophysical hazards professor at University College London’s Benfield Hazard Research Centre.
Gulf Stream Disruption Could Freeze Europe and North America

Computer models simulating ocean-atmosphere climate dynamics indicate that the
North Atlantic region would cool between three and five degrees Celsius if Conveyor circulation were totally disrupted. “It would produce winters twice as cold as the worst winters on record in the eastern United States in the past century,” says Robert Gagosian of the Woods Hole Oceanographic Institution.
Gulf Stream Linked to Previous Temperature Changes

The slowing of the
Gulf Stream has been directly linked with dramatic regional cooling before, says McGuire. “Just 10,000 years ago, during a climatic cold snap known as the Younger Dryas, the current was severely weakened, causing northern European temperatures to fall by as much as 10 degrees Fahrenheit,” he says. And 10,000 years earlier—at the height of the last ice age when most of northwestern Europe was a frozen wasteland—the Gulf Stream had just two-thirds of the strength it has now.
Could Weakened Gulf Stream Help Offset Global Warming?

A less dramatic prediction sees the
Gulf Stream slowing down but not stopping entirely, causing the east coast of North America and northwestern Europe to suffer only minor winter temperature dips. And some scientists even put forth the optimistic hypothesis that the cooling effects of a weakened Gulf Stream could actually help offset the higher temperatures otherwise caused by global warming.
Global Warming: A Planetary Experiment

To McGuire, these uncertainties underscore that fact that
 human-induced global warming is “nothing more nor less than a great planetary experiment, many of the outcomes of which we cannot predict.” Whether or not we can trim our addiction to fossil fuels might just be the determining factor in whether global warming wreaks havoc around the world, or just causes us minor annoyances.
GOT AN ENVIRONMENTAL QUESTION? Send it to: EarthTalk, c/o E/The Environmental Magazine, P.O. Box
5098, Westport, CT 06881; submit it at:www.emagazine.com/earthtalk/thisweek/, or e-mail:
 earthtalk@emagazine.com.