While scientists can't yet find a clear signal between global warming and killer tropical storms like Haiyan, the supertyphoon could well be a sign of what's to come in a warmer world

NASA / NOAA A satellite image shows Supertyphoon Haiyan over the Philippines

Some 6,000 miles away from the Philippines, where 10,000 people or more may have been killed by Supertyphoon Haiyan, the Filipino diplomat Yeb Sano rose today in Warsaw to address the international delegates at the opening session of the annual U.N. summit on climate change. In an emotional speech, Sano connected the devastation from Haiyan — quite possibly the strongest storm ever recorded upon landfall — and the intensifying threat of climate change:

Typhoons such as Yolanda (Haiyan) and its impacts represent a sobering reminder to the international community that we cannot afford to procrastinate on climate action. Warsaw must deliver on enhancing ambition and should muster the political will to address climate change. In Doha, we asked, “If not us then who? If not now, then when? If not here, then where?” (borrowed from Philippine student leader Ditto Sarmiento during Martial Law). It may have fell on deaf ears. But here in Warsaw, we may very well ask these same forthright questions. “If not us, then who? If not now, then when? If not here in Warsaw, where?” What my country is going through as a result of this extreme climate event is madness. The climate crisis is madness.

Sano was hardly the only one to connect the unimaginable power of Haiyan with global warming. U.N. Framework Convention on Climate Change head Christiana Figueres, who will help oversee the Warsaw talks, said the typhoon was part of the “sobering reality” of global warming. The sheer power of Haiyan, as well as the still uncounted human devastation it has wrought, all but assures that the supertyphoon will become a symbol of climate change for years to come, just as Hurricane Katrina and Superstorm Sandy have.

But how much of a role did current climate change actually play in the making of Haiyan? That’s less clear.



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The warming of air and sea temperatures — which is well under way — should on the whole give more power to tropical cyclones, in part because warmer air can hold more water vapor. But the reality is that the science around increasing greenhouse-gas emissions and tropical cyclones has become muddier in recent years. (Hurricanes, cyclones and typhoons are all tropical cyclones — the name just refers to where in the world they form, with tropical cyclones in the Pacific being called typhoons.) The most recent report from the Intergovernmental Panel on Climate Change (IPCC), released in September, found that there was “low confidence in attribution of changes in tropical cyclone activity to human influence” so far. The report also had “low confidence” that there would be increases in intense tropical-cyclone activity over the next few decades, and found that it was “more likely than not” that such a signal would be seen by the end of the 21st century.

In IPCC speak, “more likely than not” means a 50% or higher probability, and it’s a step back from the IPCC’s 2007 climate-change assessment, when the scientific group found that it was “likely” that future tropical cyclones would become more intense with global warming. (Likely in IPCC speak means a probability of 66% or above, and no, I don’t know why it requires a glossary to decode IPCC-speak.) That change, along with the robust scientific debate around the connection between climate change and tropical-cyclone strength and frequency, has to do with conflicting studies as well as poor historical data around tropical cyclones — especially in the less studied Pacific — which makes it hard to judge whether storms really have been getting worse as the planet has warmed. Even in places where the IPCC is much more certain that tropical cyclones have been getting more stronger and more frequent in recent decades, like the North Atlantic, scientists disagree on exactly why that’s happening.

Still, if existing climate change played a role in supercharging Haiyan, it’s likely tiny, as NASA climatologist Bill Patzert told the Pasadena Star-News:

The fingerprint is very small, if at all. If the winds are 200 mph, global warming might have contributed 5 mph to that 200 mph.

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The reality is that it remains extremely difficult to attribute specific weather events to climate change, and such attribution studies take time. It seems likely Haiyan would have been nearly as destructive whether or not the planet had warmed over the past century. It’s true that sea-level rise will have added to the massive storm surges that seem to have been the real killers in Haiyan. Seas have been rising significantly faster in the Philippine Sea, where Haiyan struck, than the world on average. The higher seas would have worsened flooding, just as sea-level rise amplified the damage from Superstorm Sandy, but given the fact that Haiyan’s storm surges were as much as 20 ft., climate-driven sea-level rise wouldn’t have been the deciding factor in the supertyphoon’s devastation.

But if it’s virtually impossible to blame Haiyan on current climate change, that doesn’t mean that future climate change — including the warming we’ve already baked into the system — won’t make future Haiyans more likely. Climate scientists are the opposites of weathermen — the further out they’re asked to forecast, the more confidence they tend to have in their predictions. Models point to stronger, if not necessarily more frequent tropical cyclones as the globe continues to warm, though that signal may not become clear until later in the 21st century.

And of course there’s debate over that as well — see this July paper by the Massachusetts Institute of Technology climatologist Kerry Emanuel, which predicted that the frequency and the intensity of tropical cyclones would increase in the 21st century, and that the increases would be most prominent in the western North Pacific, which is where Haiyan struck. The back-and-forth over today’s storms shouldn’t obscure the fact that climate change will bring an assortment of dangers, possibly including more powerful storms — which is one more reason why we need to reduce greenhouse-gas emissions while building a world that is more resilient to extreme weather. That’s especially true for poor, geographically exposed countries like the Philippines, which is already one of the most vulnerable nations in the world to climate change.

Delegates at over 190 countries will be meeting in Warsaw over the next two weeks to do just that, although expectations for the international climate talks are even dimmer than usual. (As the veteran climate-talks expert Alden Meyer of the Union of Concerned Scientists put it: “Never have the stakes been higher with expectations so low.”) In the meantime, what the Philippines needs now, more than action at Warsaw, is help on the ground — and in the future, foreign aid that can help build resistance to extreme weather, which can make the difference between a weather disaster and a human catastrophe.

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