Global Warming May Have Caused Heatwaves Killing Thousands Of People
By Countercurrents.org
27 February 2013
Countercurrents.org
Global warming may have caused extreme events such as a 2011 drought in the US and a 2003 heatwave in Europe by slowing vast, wave-like weather flows in the northern hemisphere, scientists said on February 26, 2013.
The study of meandering air systems that encircle the planet adds to understanding of extremes that have killed thousands of people and driven up food prices in the past decade.
Such planetary airflows, which suck warm air from the tropics when they swing north and draw cold air from the Arctic when they swing south, seem to be having slowed more often in recent summers and left some regions sweltering, they said.
"During several recent extreme weather events these planetary waves almost freeze in their tracks for weeks," wrote Vladimir Petoukhov, lead author of the study at the Potsdam Institute for Climate Impact Research in Germany.
"So instead of bringing in cool air after having brought warm air in before, the heat just stays," he said in a statement of the findings in the US journal Proceedings of the National Academy of Sciences.
A difference in temperatures between the Arctic and areas to the south is usually the main driver of the wave flows, which typically stretch 2,500km- 4,000km (1,550-2,500 miles) from crest to crest.
But a build-up of GHG in the atmosphere, blamed on human activities led by use of fossil fuels, is heating the Arctic faster than other regions and slowing the mechanism that drives the waves, the study suggested.
Weather extremes in the past decade include a European heatwave in 2003 that may have killed 70,000 people, a Russian heatwave and flooding in Pakistan in 2010 and a 2011 heatwave in the United States, the authors added.
The authors wrote that they proposed "a common mechanism" for the generation of waves linked to climate change.
Past studies have linked such extremes to global warming but did not identify an underlying mechanism, said Hans Joachim Schellnhuber, director of the Potsdam Institute and a co-author, who called the findings "quite a breakthrough," he wrote. The scientists added that the 32-year-period studied was too short to predict future climate change and that natural variations in the climate had not been ruled out completely as a cause.
The study only considered the northern part of the globe, in summertime. Petoukhov led another study in 2010 suggesting that cold snaps in some recent winters in Europe were linked to low amounts of ice in the Arctic Ocean.
Loss of labor capacity
Another Reuters report [2] said:
Earth's increasingly hot, wet climate has cut the amount of work people can do in the worst heat by about 10% in the past six decades, and that loss in labor capacity could double by mid-century, US government scientists reported on February 24, 2013.
Because warmer air can hold more moisture than cooler air, there is more absolute humidity in the atmosphere now than there used to be. And as anyone who has sweltered through a hot, muggy summer knows, it's more stressful to work through hot months when the humidity is high.
To calculate the stress of working in hotter, wetter conditions, experts from the US National Oceanic and Atmospheric Administration looked at military and industrial guidelines already in place for heat stress, and set those guidelines against climate projections for how hot and humid it is likely to get over the next century.
Their findings were stark: "We project that heat stress-related labour capacity losses will double globally by 2050 with a warming climate," said the lead author, John Dunne of NOAA's Geophysical Fluid Dynamics Laboratory in Princeton.
Work capability is already down to 90% during the hottest and most humid periods, Dunne and his co-authors wrote in the journal Nature Climate Change. Using a middle-of-the-road projection of future temperature and humidity, they estimate that could drop to 80% by 2050.
A more extreme scenario of future global warming, which estimated a temperature rise of 6C, would make it difficult to work in the hottest months in many parts of the world, Dunne said.
Labor capacity would be all-but eliminated in the lower Mississippi Valley and most of the United States east of the Rocky Mountains would be exposed to heat stress "beyond anything experienced in the world today", he said.
Under this scenario, heat stress in New York City would exceed that of present-day Bahrain, while in Bahrain, the heat and humidity could cause hyperthermia – potentially dangerous overheating – even in sleeping people who were not working at all.
Humans are endothermic creatures, which means they give off heat. If they can't get rid of it faster than they create it, they go into hyperthermia. Typically, humans cool off by doing less heat-producing activity, but it may get so hot and humid that even a sleeping person wouldn't be able to dissipate heat fast enough.
"This planet will start experiencing heat stress that's unlike anything experienced today," said Ronald Stouffer, a co-author of the study.
The only way to retain labor capacity, Dunne said, is to limit global warming to less than 3C.
Global average temperature has risen by about 0.7C compared to pre-industrial times. It is likely to rise another 1C by mid-century, Dunne said.
The way some workers already adapt to heat stress – taking a siesta during the hottest hours of the day, working outdoor jobs like construction at night when temperatures drop or ceasing work entirely during periods of peak heat and humidity – could migrate to places where heat stress is increasing.
The US west coast and northern Europe are likely to be two of the regions that will be affected last by the trend toward more hot and humid climate, the scientists said.
Part of the issue is how well-adapted certain regions are to extreme heat stress, Dunne said.
As an example, he noted that 70,000 people were killed during a disastrous 2003 heatwave in Europe, where heat stress was highly unusual. However, the same kind of stress was normal for a place like India, where a similar heatwave killed 3,000.
"It's very regionally dependent and highly determined by adaptation," Dunne said.
Source:
[1] guardian.co.uk, Feb 26, 2013, “Global warming and airflow changes 'caused US and EU heatwaves'”,
http://www.guardian.co.uk/environment/2013/feb/26/global-warming-planetary-airflow-extreme-weather-us-eu
[2] guardian.co.uk, Feb 25, 2013, “Hotter, wetter climate slashes labour capacity by 10%, study shows”,
http://www.guardian.co.uk/environment/2013/feb/25/hot-climate-labour-capacity
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