Analysis: Evidence for climate extremes, costs, gets more local

OSLO Fri Jul 27, 2012 10:23am EDT

A pedestrian walks across a bridge above a main road on a day with high air pollution in Beijing June 6, 2012. REUTERS/David Gray

A pedestrian walks across a bridge above a main road on a day with high air pollution in Beijing June 6, 2012.

Credit: Reuters/David Gray

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OSLO (Reuters) - Scientists are finding evidence that man-made climate change has raised the risks of individual weather events, such as floods or heatwaves, marking a big step towards pinpointing local costs and ways to adapt to freak conditions.

"We're seeing a great deal of progress in attributing a human fingerprint to the probability of particular events or series of events," said Christopher Field, co-chairman of a U.N. report due in 2014 about the impacts of climate change.

Experts have long blamed a build-up of greenhouse gas emissions for raising worldwide temperatures and causing desertification, floods, droughts, heatwaves, more powerful storms and rising sea levels.

But until recently they have said that naturally very hot, wet, cold, dry or windy weather might explain any single extreme event, like the current drought in the United States or a rare melt of ice in Greenland in July.

But for some extremes, that is now changing.

A study this month, for instance, showed that greenhouse gas emissions had raised the chances of the severe heatwave in Texas in 2011 and unusual heat in Britain in late 2011. Other studies of extremes are under way.

Growing evidence that the dice are loaded towards ever more severe local weather may make it easier for experts to explain global warming to the public, pin down costs and guide investments in everything from roads to flood defenses.

"One of the ironies of climate change is that we have more papers published on the costs of climate change in 2100 than we have published on the costs today. I think that is ridiculous," said Myles Allen, head of climate research at Oxford University's Environmental Change Institute.

"We can't (work out current costs) without being able to make the link to extreme weather," he said. "And once you've worked out how much it costs that raises the question of who is going to pay."

Industrialized nations agree they should take the lead in cutting emissions since they have burnt fossil fuels, which release greenhouse gases, since the Industrial Revolution. But they oppose the idea of liability for damage.

Almost 200 nations have agreed to work out a new deal by the end of 2015 to combat climate change, after repeated setbacks. China, the United States and India are now the top national emitters of greenhouse gases.

Field, Professor of Biology and Environmental Earth System Science at the University of Stanford, said that the goal was to carry out studies of extreme weather events almost immediately after they happen, helping expose the risks.

"Everybody who needs to make decisions about the future - things like building codes, infrastructure planning, insurance - can take advantage of the fact that the risks are changing but we have a lot of influence over what those risks are."


Another report last year indicated that floods 12 years ago in Britain - among the countries most easily studied because of it has long records - were made more likely by warming. And climate shifts also reduced the risks of flooding in 2001.

Previously, the European heatwave of 2003 that killed perhaps 70,000 people was the only extreme where scientists had discerned a human fingerprint. In 2004, they said that global warming had at least doubled the risks of such unusual heat.

The new statistical reviews are difficult because they have to tease out the impact of greenhouse gases from natural variations, such as periodic El Nino warmings of the Pacific, sun-dimming volcanic dust or shifts in the sun's output.

So far, extreme heat is the easiest to link to global warming after a research initiative led by the U.S. National Oceanic and Atmospheric Administration and the British Meteorological Office.

"Heatwaves are easier to attribute than heavy rainfall, and drought is very difficult given evidence for large droughts in the past," said Gabriele Hegerl of the University of Edinburgh.

Scientists often liken climate change to loading dice to get more sixes, or a baseball player on steroids who hits more home runs. That is now going to the local from the global scale.

Field said climate science would always include doubt since weather is chaotic. It is not as certain as physics, where scientists could this month express 99.999 percent certainty they had detected the Higgs boson elementary particle.

"This new attribution science is showing the power of our understanding, but it also illustrates where the limits are," he said.

A report by Field's U.N. group last year showed that more weather extremes that can be linked to greenhouse warming, such as the number of high temperature extremes and the fact that the rising fraction of rainfall falls in downpours.

But scientists warn against going too far in blaming climate change for extreme events.

Unprecedented floods in Thailand last year, for instance, that caused $45 billion in damage according to a World Bank estimate, were caused by people hemming in rivers and raising water levels rather than by climate change, a study showed.

"We have to be a bit cautious about blaming it all on climate change," Peter Stott, head of climate monitoring and attribution at the Met Office's Hadley Centre, said of extremes in 2012.

Taken together, many extremes are a sign of overall change.

"If you look all over the world, we have a great disastrous drought in North America ... you have the same situation in the Mediterranean... If you look at all the extremes together you can say that these are indicators of global warming," said Friedrich-Wilhelm Gerstengabe, a professor at the Potsdam Institute for Climate Impact Research.

(Additional reporting by Sara Ledwith in London; Editing by Louise Ireland)

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Comments (25)
Since 1850, humans have dug billions of tons of coal, pumped trillions of barrels of oil, and pumped trillions of cubic meters of gas out of the earth and burned it into the air. There are 7 billion humans on earth, and the number should rise to 9 billion by 2050. Between the massive industrialization and the growth in population, enormous amounts of gases have been put into the air that were not put into the air in these quantities in previous millennia on earth.

In addition, the 7 to 9 billion humans want or will want to live like Americans. President Lula da Silva of Brazil said that his people were not going to just sit under trees while the West lived in luxury. The current situation is difficult, and the future looks worse unless people make improvements. However, this offers new opportunities in technologies that improve the situation because they will be growth industries that will expand because there are too few of them at the present time.

Jul 28, 2012 3:43pm EDT  --  Report as abuse
TheNewWorld wrote:
“said Christopher Field, co-chairman of a U.N. report due in 2014 about the impacts of climate change.”

Wow co-chairman of a U.N. report. You can’t scientically say these things would not happen if man did not exist. The fact is the sun has been very active in recent years. We were told in the 60s-70s that the earth was headed for an ice age. We were told in the 80s that in 20 years the brooklyn bridge would be under water. Forgive me if I don’t believe the boy who keeps calling wolf and asking for more money for more reports. Not to mention is pushing an agenda for the largest transfer of wealth from industrialized nations to non industrialized nations through carbon credits which will do nothing to stop the green house gases.

Jul 28, 2012 5:07pm EDT  --  Report as abuse
TheNewWorld wrote:

You have hit the real issue. Too much population. That is the easiest to fix. Personally I think 1 child is plenty. I find it a shame that many of those who have little means have larger numbers of children. I guess it is an instinct from the days where infant mortality was much higher. Either way cutting the earth’s population in half would go a long, long way in reducing pollution and resource usage. Why are environmentalist afraid to address the real danger facing the planet? We don’t need carbon tax, we need taxes on children, and birth control/temporary sterilization/free permanent sterilization everywhere on the planet. You get one kid, that is it. Why the US sees fit to give rewards for more kids I have no idea.

Jul 28, 2012 5:12pm EDT  --  Report as abuse
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