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Asking if Cyclone Pam Was Caused by Climate Change Is the Wrong Question, Say Scientists

The storm left at least 24 people dead and several of Vanuatu's islands without freshwater supplies, highlighting the need for better risk preparedness around the world, as extreme weather events become more severe.

by Laura Dattaro
Mar 17 2015, 10:10pm

Photo by Dave Hunt/Reuters

When Cyclone Pam ripped through the South Pacific on Saturday morning, it not only left behind a trail of destruction on the 83-island nation of Vanuatu. In the storm's wake, political leaders around the world have used the event as an opportunity to highlight the need to address climate change and help poor, low-lying nations to adapt to rising seas and more severe weather extremes.

Vanuatu's president Baldwin Lonsdale wasted little time in identifying the culprit behind his country's acute humanitarian disaster, which has left at least 24 people dead and left some islands without freshwater supplies.

"We see the level of sea rise. … The cyclone seasons, the warm, the rain, all this is affected," Lonsdale said. "Yes, climate change is contributing to this."

Wind speeds during the cyclone reached 186 miles per hour, earning Pam a Category 5 classification — the highest level.

The exact impact of climate change on cyclones in the South Pacific remains uncertain. But scientists say that warming ocean temperatures are likely boosting storm intensity.

"We've really altered the atmosphere, we've altered the radiative balance, I'm sure we've altered these storms," Andrew Dessler, an atmospheric scientist at Texas A&M University, told VICE News. "Is it one mile per hour faster winds or 30 mile per hour faster winds? At present, that's not available."

Related: Tropical Cyclone Pam pummels Pacific islands

Cyclones form over warm waters, and the warmer the water, the more water vapor in the atmosphere. That gives the storm more energy, Dessler said.

A 2014 study by the National Oceanic and Atmospheric Administration (NOAA) found that changes in both ocean and atmospheric temperatures had combined to substantially increase the potential intensity of storms in the area where Pam hit.

Asking if Cyclone Pam was caused by climate change, say scientists, elides a more important question: What is the probability of future extreme weather events occurring, whether tropical storms or droughts? 

"An individual event is more difficult to ascribe or attribute to climate change, but when you step back and look at the how the probability of these events is changing, that's a much stronger argument," James Kossin, a tropical cyclone specialist with NOAA, told VICE News. "These events are consistent with what we expect with climate change, and the probability of this type of event will likely increase."

Focusing on that larger picture, and the shifting risk from intense storms, may ultimately be more useful for public discussion and developing strategies for addressing climate change than assigning a cause to any single catastrophic event, Kossin said. That's especially true in a political climate where politicians purposefully conflate climate with weather in order to claim climate change isn't happening, as Oklahoma Senator James Inhofe recently did when throwing a snowball on the floor of the US Senate.

"What happens is that we get caught up in basically a climate change blame game every time an individual extreme weather event comes up," Aaron Huertas, a climate science communications officer with the Union of Concerned Scientists, told VICE News. "Sometimes that can be a really good opportunity for scientists to talk about the bigger trend that they do see between climate change and certain types of extreme weather. That said … I think the discussion can get a little misleading and unnecessarily heated."

Related: Extreme weather displaces far more people than war and it's getting worse

While scientists continue to research the links between climate change and the intensity and frequency of cyclones, it's clear that those storms are forming over rising sea levels. That means a storm of any intensity could bring more coastal flooding, simply because it's occurring over already higher seas. For example, when Hurricane Sandy hit New York City its nine-foot storm surge occurred on waters that were a foot higher than they were a century ago, partly due to climate change.

Improved risk awareness could infuse international climate negotiations with a sense of urgency — and help city managers on the local level to develop methods for adapting to climate change, Huertas said.

"There are all these almost kind of boring but incredibly important questions that climate science should be making us ask," Huertas told VICE News. "And I worry that the focus on individual events kind of distracts us from that."

Follow Laura Dattaro on Twitter: @ldattaro