Muddy Waters

Aerial_view_of_Tacloban_after_Typhoon_Haiyan

An aerial view of the devastation caused by Typhoon Haiyan in Tacloban, Philippines (Photo: Russell Watkins/Department for International Development)

As Typhoon Haiyan barreled down on the Philippines last month, another storm was forming – on Twitter.

“Climate liars like Rupert Murdoch & Koch Brothers have more & more blood on their hands as climate disasters claim lives across world,” tweeted Jeffrey Sachs, Director of the Earth Institute at Columbia University.

In response, Roger Pielke Jr., an environmental studies professor at the University of Colorado, tweeted, “Wow @JeffDSachs Big claim. Just hyperbole on your part? Or do you have any evidence of causality between these 3 people & disaster deaths?”

Pielke, along with many climate scientists, is hesitant to attribute the increasing toll of extreme weather events to human-caused climate change. He elaborated on his position in an article published in The Guardian’s political science section on November 19:

“The Intergovernmental Panel on Climate Change has recently issued two major assessments on extreme weather. Its report issued last month found little evidence to support claims that tropical cyclones (that is, hurricanes and typhoons), floods, drought, winter storms or tornadoes had become more frequent or intense. In the Western Pacific, where Haiyan occurred, in addition to a decreasing number of landfalls, the strongest storms have actually become weaker in recent decades, according to a recent analysis.”

However, some climate scientists are starting to draw connections between climate change and extreme weather events. Environmental scientist Dana Nuccitelli, who blogs for SkepticalScience.com and The Guardian, took issue with Pielke’s analysis.

“Climate scientists are confident in three ways that climate change will make the impacts of hurricanes [and typhoons] worse,” he wrote in a piece for The Guardian’s “Climate Consensus – The 97%” blog.

According to Nuccitelli, tropical cyclones feed off of ocean heat, which means that warmer ocean surface temperatures due to climate change contribute to the relative strength of these storms. In addition, increasing ocean temperatures cause thermal expansion which leads to sea level rise. Nuccitelli writes that global sea level rise, on the order of roughly eight inches since 1880, and rising, amplifies storm surges and flooding associated with hurricanes and typhoons.

National Oceanic and Atmospheric Administration satellite data shows that sea level rise in the western Pacific Ocean, where Haiyan formed, increased at a rate of roughly nine millimeters per year from 1993 to 2012, nearly three times the global average.

NOAA Sea Level Trend 1993-2012

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In describing the relationship between tropical cyclones and increased moisture in the atmosphere due to climate change, Nuccitelli defers to National Center for Atmospheric Research climate scientist Kevin Trenberth’s analysis of Hurricane Sandy:

“With every degree F [Fahrenheit] rise in temperatures, the atmosphere can hold 4 percent more moisture. Thus, [Hurricane] Sandy was able to pull in more moisture, fueling a stronger storm and magnifying the amount of rainfall by as much as 5 to 10 percent compared with conditions more than 40 years ago. Heavy rainfall and widespread flooding are a consequence.”

NOAA climate models also project that the western Pacific Ocean will outpace the rest of the world in increased precipitation due to climate change this century.

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But in its latest report, the IPCC cautiously summarized that while upward trends in some areas can be detected, interpretation of longer-term trends is constrained by “data quality concerns.”

“Assuming model predictions for future changes in tropical cyclone behavior are perfectly accurate, it will be many decades, even centuries, before such a signal can be detected in trend data,” said Pielke.

While no scientific consensus currently exists surrounding the relationship between climate change and tropical cyclones, extreme weather events do present a unique opportunity for scientists to communicate with the public about the Earth’s changing climate, says Max Boykoff, a colleague of Pielke’s at the University of Colorado’s Center for Science and Technology Policy Research.

“Looking into the social science research of what has resonance with people, what actually takes a diffuse, long-term, often times distant threat, and brings it home, makes it relevant in people’s everyday lives, these extreme weather events are focusing events that make these [climate change] issues very real for a variety of people,” he said.

In a Tweet on November 12, Andrew Freedman, a science writer at Climate Central, concluded upon the contentious debate with a call for action: “Bottom line of all the #Haiyan and climate change talk is that we need to improve resilience to extreme events regardless!”

Hopefully that’s something that everyone can agree on.

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