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

OSLO Fri Jul 27, 2012 7:53pm IST

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

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)

We welcome comments that advance the story through relevant opinion, anecdotes, links and data. If you see a comment that you believe is irrelevant or inappropriate, you can flag it to our editors by using the report abuse links. Views expressed in the comments do not represent those of Reuters. For more information on our comment policy, see
Comments (4)
DennisVictor wrote:
Blaming some of the costs from weather events on climate change is reasonable. Imputing climate change to Human activity alone is wild assumption at this point. Estimates on costs for the conditions in 2100 or 88 years from now is hilarious.
Trying to pin down a cost for a storm before it happens is pure speculation.
Accurate and comprehensive data to base rate of change has not been collected over long term. Every computer model used to predict the future uses unproven assumption at it’s heart. The susceptibility of the climate to change is the most basic assumption and there is no verification that the assumption is accurate or even plausible. This is approximately as valid as predicting the net income of your great grandchildren for their last year before retirement when you marry. It is not science but speculation. Made more absurd with each passing attempt to use it as basis for culpability and wealth redistribution from wealthy nations to poor neighbors.

Jul 29, 2012 5:40pm IST  --  Report as abuse
DennisVictor wrote:
It is reasonable to attribute more severe weather to a warming climate. To attribute it to Man’s activity is another degree of separation. The actual percentage of climate change caused by man is speculative. Solar output is only recently been monitored in a quantitative way. The relative amount of heating that can be attributed to increased solar output is unknown due to lack of historic measurements. Assumptions of unproven reliability are built in to every computer model used for prediction of climate change. To base a cost analysis off unverifiable data is an exercise in propaganda, Not Science. Seeded in this article are Man Made global warming references and Global warming. The two are very different and should not be intermixed.

Jul 29, 2012 6:43pm IST  --  Report as abuse
rmuldavin wrote:
“Higgs Boson Elementary Particle” [HBEP] even if 99.999 percent pure,
yes it can float, for it is the ultimate “connector” to every other
particle in “the Universe”.

How’s that? Yes Gravity is postulated to connect to every other
particles by a “string”, very dense as well as very small diameter, called by
many a “weak force” relative other forces.

“Entanglement” is a word used to describe the, for large accelerators, the two largest circular ones, and the forgotten news that a linear one exist at Stanford, CA, and a smaller circular one one at the Berkeley, UCB campus.

The photon “energy” that travels in space and time like a coil of very dense mass, and connects to another former partner (like positive charge [+] to a negative [-], I conclude

And surprise of surprises that mass of the helical coil transfers that energy to it partner, positive or negative, like E=mc^2, at least in orbit around the nucleus.

This kind of energy is often called “mass-less” that appears in literature as “photons” and maybe “gravitons”.

Apparently my attempts to “Add your comment” occurred using the mention of the
HBEB. i.e. we are all connected. Best rm

Jul 29, 2012 6:02am IST  --  Report as abuse
This discussion is now closed. We welcome comments on our articles for a limited period after their publication.

  • Most Popular
  • Most Shared