Political waves from Typhoon Haiyan have washed up in Poland, where the Philippines' lead negotiator at a UN summit made an emotional plea for action on climate change. The appeal, however, is unlikely to tear the scientific debate from its moorings.
In a speech in Warsaw to the UN Climate Change Convention's 19th Conference of the Parties, Filipino diplomat Naderev Sano challenged anyone who continues to deny climate change to visit his ravaged country - then launched a hunger strike to demand results.
Yet divisions about whether extreme weather events can be blamed on climate change are evident in the reaction of scientists to the catastrophic storm. Haiyan has generated rare common ground on which prominent figures share a reluctance to make direct causal links.
Super Typhoon Haiyan was one of the most powerful storms ever recorded on land, and although the official death toll now stands at more than 2,300, aid workers fear this will rise.
"Storms happen and always have and always will, so you can't say that this storm could not have happened if it weren't for climate change," said Professor Myles Allen of Oxford University's Environmental Change Institute.
"What you can say is that climate change might be affecting the risk of the most intense hurricanes - but at the moment that science is still in its infanc," added Allen, himself a contributor to the latest Intergovernmental Panel on Climate Change (IPCC) report.
One cannot tie a particular weather event like this to any climate effect, it's impossible.
Professor Matthew Collins of Exeter University, another IPCC contributor, added: "Climate change refers to the average change over many years over many weather events. It’s difficult to say in this case whether this event has been exacerbated by climate change, but we certainly could not say that it would have been caused by it."
Such understandable scientific caution is fertile territory for leading sceptics such as Professor Fred Singer of the University of Virginia, a trenchant critic of the IPCC and the whole notion of man-made climate change.
"One cannot tie a particular weather event like this to any climate effect, it’s impossible. Secondly, there hasn’t been any warming for at least 15 years, so it couldn’t be due to global warming. And third, this particular typhoon, called Yolanda in the Philippines, is not unusual, and something like this occurs every couple of years."
A key question that has emerged is the degree to which the typhoon was exceptional - the Philippines is prone to extreme events and Haiyan was the third huge storm to strike in a year. Scholars more sceptical about the idea of man-made climate change suggest the event may reflect longer, established weather patterns.
John Christy is the director of the Earth System Science Center at the University of Alabama in Huntsville, and a lead author of an IPCC report in 2001. "The long-term record shows no increase in frequency or severity of tropical storms in this region or worldwide," he said.
"Blaming this on global warming is a quick and easy answer to the question of ‘why did this happen?’ Unfortunately, it is the wrong answer - these cyclones have happened before, are happening, and will continue to happen."
Professor Judith Curry, chair at the Georgia Institute of Technology's School of Earth and Atmospheric Sciences, agreed.
"The Philippines is struck by typhoons on average of five times per year, and there is no trend - peak numbers of landfalls occurred in the 1960s and 1970s... The bottom line is that there is nothing particularly unusual about Haiyan that could be attributed to global warming."
|Children hold signs asking for food in Cebu province [Reuters]
The latest IPCC report underscored the changing risk of extreme weather events, and confidence among scientists remains low for long-term changes in tropical cyclone activity.
The think-tank Germanwatch said extreme weather events are on the rise globally.
"We have seen a number of very unusual weather events since 2000 and especially since 2007," said its policy director Christoph Bals, speaking from the Warsaw talks.
"There have been a high number of extreme events which are either 100-year events or even 1,000-year events around the world from Russia to Australia and from Pakistan to Texas and from Europe now to the Philippines. And for many of them, there is a high or medium likelihood that they cannot be explained without climate change."
Although scientists argue extreme weather such as Haiyan may not ultimately become more common, there is significant expectation that when it occurs it will be more intense.
The argument linking such events with climate change is based on the impact of warming oceans, which give storms their energy, and research suggests the Pacific Ocean's temperature is rising.
A key figure in the global warming debate, Professor James Hansen of the Department of Earth and Environmental Sciences at Columbia University, said: "The statement that I have been making for decades is that storms fuelled by the latent energy in water vapour - thunderstorms, tornadoes, tropical storms - have the potential to be stronger, to have faster winds, as the planet warms, because the warmer atmosphere holds more water vapour. That is a safe statement. It does not mean every storm will be stronger, but the strongest storms will be stronger than the strongest storm in the past.
"My own opinion is that we can combine the still-limited empirical evidence with well-grounded theoretical expectations to conclude that global warming is already affecting the occurrence of strong storms, and thus global warming should be given part of the blame for extreme events."
Warming seas explain why Professor Piers Forster of Leeds University, also an IPCC contributor, said he believes the position taken by the Philippines in Warsaw is reasonable.
|A surivor walks among the debris of destroyed houses [AFP]
"Science tells us that tropical storms are more intense because of climate change. They are not necessarily happening more often, but when they do happen they have more energy and will do more damage. Simply, sea surface temperatures are warmer, and these give the storms more energy, leading to stronger winds."
While there is evidence that the intensity of storms around countries such as the Philippines has increased, there is insufficient data to link any particular weather event to climate change.
But some scientists believe that, with sufficient resources, it could be possible to gain a much clearer picture of cause and effect.
"The key point is we should be able to answer the Philippine government’s question and there’s nothing in principle stopping us doing so, only resources, but it’s a question well worth answering," said Allen.
In the meantime, scientists are approaching the issue in terms of risk and likelihood.
But if Haiyan is unlikely to shake up the science on climate change, it does serve as a timely reminder that coastal regions are vulnerable to cyclones and being prepared is key.
Sceptics such as Singer insist the case can underline how opposition to cheap energy limits the degree to which economic growth can strengthen a country’s preparedness.
Nobody has any idea what the global inventory of impacts is: who is being affected by climate change today. I find that surprising.
"What it shows is it pays to be prepared for unusual events, be they typhoons, earthquakes, tsunamis and so on. We should be prepared for all sorts of emergencies and this requires a high level of income and economic growth, and I’m afraid that we’re moving in the opposite direction.
"By robbing us of cheap energy, by concentrating on wind and solar instead of using gas oil and coal, we are really robbing people of the wherewithal to prepare for real emergencies. I think our policies are counterproductive."
Nonetheless, the timing of Typhoon Haiyan has pushed the theme of climate change back up the agenda after a period in the doldrums, injecting new energy into the Warsaw talks.
Sano's intervention also coincides with a growing focus in climate research on the damage in the here and now caused by extreme events.
"We put a lot of resources into compiling global inventories of who is contributing to the problem, which countries are pumping out how much greenhouse gases, yet nobody has any idea what the global inventory of impacts is: who is being affected by climate change today," said Allen. "I find that surprising."