[Marxism] Human-Related Climate Change Led to Extreme Heat in Australia, Scientists Say

Louis Proyect lnp3 at panix.com
Mon Sep 29 13:19:04 MDT 2014

NY Times, Sept. 29 2014
Human-Related Climate Change Led to Extreme Heat, Scientists Say

The savage heat waves that struck Australia in 2013 were almost 
certainly a direct consequence of the human release of greenhouse gases, 
researchers said Monday. It is perhaps the most definitive statement 
climate scientists have made that ties a specific weather event to 
global warming.

Five groups of researchers, using distinct methods, analyzed the heat 
that baked Australia for much of last year and continued into 2014, 
shutting down the Australian Open tennis tournament at one point in 
January. All five came to the conclusion that last year’s heat waves 
could not have been as severe without the long-term climatic warming 
caused by human activity.

“When we look at the heat across the whole of Australia and the whole 12 
months of 2013, we can say that this was virtually impossible without 
climate change,” said David Karoly, a climate scientist at the 
University of Melbourne who led one research team.

Three other research groups analyzed the drought afflicting California, 
but could not come to a unanimous conclusion about whether the odds had 
been increased by human emissions. One paper found that they had been; 
two others found no clear evidence of that.

Researchers generally agreed, however, that regardless of the cause, the 
effects of the California drought have been made worse by global 
warming. That is because whatever rain does fall in California tends to 
evaporate faster in the hotter climate, leading to drier conditions.

Two dozen papers analyzing weather extremes from 2013 were published on 
Monday in the Bulletin of the American Meteorological Society. This look 
back at the prior year has become an annual event, as scientists 
increasingly try to answer the question many ordinary people are asking 
after every extreme weather event: Did climate change have anything to 
do with it?

For numerous events in 2013, they were able to rule that out. Even 
though the overall global warming trend has been definitively linked to 
human emissions in scores of papers, the new reports show that the 
frequent rush to attribute specific weather events to human activity is 
not always well grounded.

For instance, one research group found that the type of extreme rainfall 
that struck parts of Colorado last September had become less likely, not 
more likely, in the warming climate. Another group found no increase in 
the likelihood of heavy rains and floods that struck parts of Central 
Europe in June that could be attributed to global warming, even though 
such claims were made at the time.

Myles R. Allen, a researcher at Oxford University in Britain whose group 
conducted the latter study, noted in an interview that the science of 
attributing specific events to human emissions was still contentious and 
difficult, so any answers given today must be regarded as provisional.

His group has found a measure of human influence on several weather 
events over the years. But with the science still emerging, he cautioned 
against the impulse to cite global warming as a cause of almost any kind 
of severe weather.

“If we don’t have evidence, I don’t think we should hint darkly all the 
time that human influence must be to blame somehow,” Dr. Allen said.

The new batch of reports analyzed extreme heat in 2013 not only in 
Australia, but also in Europe, China, Japan and Korea, with the 
researchers concluding in every case that global warming had made the 
occurrence of the heat extremes more likely.

In the Australian case, computers were used to analyze what the climate 
would likely be in the absence of human emissions. They were simply 
unable to produce a year as extreme as 2013, and other analytical 
methods yielded similar answers.

But computer analyses that factored in greenhouse gases and the warming 
they are causing showed an increasing likelihood of extraordinary heat 
waves in Australia.

“Five reports all showing the same thing is a very powerful signal,” 
said Thomas C. Peterson, principal scientist at the National Climatic 
Data Center in Asheville, N.C., a unit of the National Oceanic and 
Atmospheric Administration.

In addition to the Colorado and central European rains, the 2013 events 
for which scientists were able to rule out a human contribution included 
a blizzard in South Dakota, heavy snowfall in the Pyrenees in Europe, 
and a cyclone that swept across northwestern Europe in late October.

The new reports come as scientists, responding to popular demand, are 
trying to speed up their analysis of extreme weather events and the role 
of greenhouse gases.

It used to take them years to come to a clear view of any particular 
event; now, papers are being published within several months. By 
sometime next year, researchers hope to reduce that to a matter of days, 
with three groups of researchers around the world training their sights 
on extreme events as soon as they occur, then putting out reports while 
the public is still discussing the aftermath.

“We want to get to this place where we can answer the question when the 
media are asking it,” said Heidi Cullen, a scientist with Climate 
Central, a news and research organization in Princeton, N.J., who is 
helping to lead the effort. “We want to give the first, best answer we 
can possibly give.”

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