15/4/13

Antarctic ice melting at record rate, study shows


The evidence comes from a 364-metre ice core containing a record of freezing and melting over the previous millennium

Press Assocition
guardian.co.uk, 



Summer ice is melting at a faster rate in the Antarctic peninsula than at any time in the last 1,000 years, a new study has shown. Photograph: Nasa/AFP/Getty Images



Summer ice is melting at a faster rate in the Antarctic peninsula than at any time in the last 1,000 years, new research has shown.
The evidence comes from a 364-metre ice core containing a record of freezing and melting over the previous millennium.
Layers of ice in the core, drilled from James Ross Island near the northern tip of the peninsula, indicate periods when summer snow on the ice cap thawed and then refroze.
By measuring the thickness of these layers, scientists were able to match the history of melting with changes in temperature.
Lead researcher Dr Nerilie Abram, from the Australian National University and British Antarctic Survey (BAS), said: "We found that the coolest conditions on the Antarctic peninsula and the lowest amount of summer melt occurred around 600 years ago.
"At that time temperatures were around 1.6C lower than those recorded in the late 20th century and the amount of annual snowfall that melted and refroze was about 0.5%.
"Today, we see almost 10 times as much (5%) of the annual snowfall melting each year.
"Summer melting at the ice core site today is now at a level that is higher than at any other time over the last 1,000 years. And while temperatures at this site increased gradually in phases over many hundreds of years, most of the intensification of melting has happened since the mid-20th century."
Levels of ice melt on the Antarctic peninsula were especially sensitive to rising temperature during the last century, he said.
"What that means is that the Antarctic peninsula has warmed to a level where even small increases in temperature can now lead to a big increase in summer melt," Abram added.
Dr Robert Mulvaney, from the British Antarctic Survey, who led the ice core drilling expedition in 2008 and co-authored a paper on the findings published on Sunday in the journal Nature Geoscience.
He said: "Having a record of previous melt intensity for the Peninsula is particularly important because of the glacier retreat and ice shelf loss we are now seeing in the area.
"Summer ice melt is a key process that is thought to have weakened ice shelves along the Antarctic peninsula leading to a succession of dramatic collapses, as well as speeding up glacier ice loss across the region over the last 50 years."
The ice core record suggested a link between accelerated melting and man-made global warming. But a different and more complex picture has emerged from another region of Antarctica.
A separate US study, published in the same journal, shows that thinning ice from the West Antarctic Ice Sheet Divide cannot confidently be blamed on greenhouse gas emissions.
An ice core record from this site indicates a strong influence from unusual conditions in the tropical Pacific during the 1990s.
In that decade, an El Niño event – a cyclical system of winds and ocean currents that can affect the world's weather – caused rapid thinning of glaciers in the west Antarctic.
The spike in temperature was little different from others that occurred in the 1830s and 1940s, which also saw prominent El Niño events.
"If we could look back at this region of Antarctica in the 1940s and 1830s we would find that the regional climate would look a lot like it does today, and I think we also would find the glaciers retreating much as they are today," said lead author Prof Eric Steig, from the University of Washington.
He said the same was not true for the Antarctic peninsula, the part of the continent closer to South America. Here, more dramatic changes were "almost certainly" a result of human-induced global warming.

9/4/13

Climate change will threaten wine production, study shows


Global warming will make it difficult to raise grapes in traditional wine country, but will shift production to other regions

Suzanne Goldenberg, US environment correspondent

The Guardian, Monday 8 April 2013 18.26 BST





A study has found sharp declines in wine production from Bordeaux, Rhone and Tuscany, as well as California’s Napa Valley and Chile by 2050, as a warming climate makes it harder to raise grapes in traditional wine country Photograph: Cephas Picture Library / Alamy/Alamy


Bid adieu to Bordeaux, but also, quite possibly, a hello to Chateau Yellowstone. Researchers predict a two-thirds fall in production in the world's premier wine regions because of climate change.

The study forecasts sharp declines in wine production from Bordeaux and Rhone regions in France,Tuscany in Italy and Napa Valley in California and Chile by 2050, as a warming climate makes it harder to grow grapes in traditional wine country.
But also anticipate a big push into areas once considered unsuitable. That could mean more grape varieties from northern Europe, including Britain, the US north-west and the hills of central China.


The most drastic decline was expected in Europe. Photograph: Conservation International


"The fact is that climate change will lead to a huge shakeup in the geographic distribution of wine production," said Lee Hannah, a senior scientist at Conservation International and an author of the study.

Researchers expect big changes in regions enjoying the cool winters and hot dry summers that produce good grapes. "It will be harder and harder to grow those varieties that are currently growing in places in Europe," Hannah said. "It doesn't necessarily mean that [they] can't be grown there, but it will require irrigation and special inputs to make it work, and that will make it more and more expensive."
Wine grapes are known to be one of the most finicky of crops, sensitive to subtle shifts in temperature,rain and sunshine. The industry has been forward-looking when it comes to anticipating the effects of climate change.
Wine experts have known for several years that a hotter, drier climate would change growing conditions in many of the most prized wine regions – forcing vineyards to mist grapes on the vine to protect them from the sun, or move sensitive vines to more hospitable terrain.
But the latest findings, published in the journal Proceedings of the National Academy of Sciences, still took the researchers by surprise. "We expected to see significant shifts, but we didn't expect to see shifts like these," said Hannah.
The scientists used 17 different climate models to gauge the effects on nine major wine-producing areas. They used two different climate futures for 2050, one assuming a worst-case scenario with a 4.7C (8.5F) warming, the other a 2.5C increase.
Both forecast a radical re-ordering of the wine world. The most drastic decline was expected in Europe, where the scientists found a 85% decrease in production in Bordeaux, Rhone and Tuscany.

The future was also bleak for wine growing areas of Australia. Photograph: Conservation International
The future was also bleak for wine growing areas of Australia, with a 74% drop, and California, with a 70% fall.
Wine growers in the Cape area of South Africa would also be hit hard, with a 55% decline. Chile's wine producers would expect losses of about 40%, the study found.


Wine growers in the Cape area of South Africa would also be hit hard. Photograph: Conservation International
But climate change would also open up other parts of the world to grapes, as growers look for higher, cooler ground, the study found.
The industry is already scoping out potential new territory such as Tasmania. The findings could lead wine growers to strike out for wilderness areas around Yellowstone Park, or even scale higher into the hills of central China.
Both areas could be prime areas for wine production, the study found.
However, that search for new wine country could in turn create a whole new set of potential problems, for the wine growers of the new frontier.
Some newly identified wine growing regions of the future are wilderness areas – such as that around Yellowstone Park in the US, where there are already clashes between ranchers and wolves. In China, the suitable wine growing regions of the future lie squarely in the hill habitat of the endangered giant panda.
Both are going to be heading for those same hills.
"Wine is going to be on the move in the future as will wildlife," said Rebecca Shaw, a scientist for the Environmental Defence Fund and an author of the paper. "This adaptation has the potential to threaten the survival of wildlife."


Climate change would also open up other parts of the world to grapes, as growers look for higher, cooler ground. Photograph: Conservation International