Sat, Oct 22, 2016 - Page 9 News List

How climate change triggers earthquakes and volcanoes

Global warming might not only be causing more destructive hurricanes, it could also be shaking the ground beneath our feet

By Bill McGuire  /  The Observer

Illustration: Lance Liu

Devastating hurricane? More than 1,000 lives lost? It must be climate change. Almost inevitably, Hurricane Matthew’s recent rampage across the Caribbean and southeastern US has been fingered by some as a backlash of global warming driven by humanity’s polluting activities, but does this really stack up?

The short answer is “No.” Blame for a single storm cannot be laid at climate change’s door, as reinforced by the bigger picture. The current hurricane season is by no means extraordinary and the past few seasons have actually been very tame. The 2013 season saw no major hurricanes at all and tied with 1982 for the fewest hurricanes since 1930. This, in turn, is no big deal as there is great year-on-year variability in the level of hurricane activity, which responds to various natural factors, such as El Nino and the Atlantic Multidecadal Oscillation, as well as the progressive warming of the oceans as climate change bites harder.

The consensus holds that while a warmer world will not necessarily mean more hurricanes, it will see a rise in the frequency of the most powerful, and therefore more destructive, variety. This view was supported recently by Kerry Emanuel, a hurricane scientist at the Massachusetts Institute of Technology, who pointed to Matthew as a likely sign of things to come.

Debate within the hurricane science community has in recent decades been almost as hostile as the storms themselves, with researchers, on occasion, even refusing to sit on the same panels at conferences. At the heart of this sometimes acrimonious dispute has been the validity of the Atlantic hurricane record and the robustness of the idea that hurricane activity had been broadly ratcheting up since the 1980s. Now, the weight of evidence looks to have come down on the side of a broad and significant increase in hurricane activity that is primarily driven by progressive warming of the climate. For many, the bottom line is the sea surface temperature, which is a major driver of hurricane activity and storm intensification. Last year saw the warmest sea temperatures on record, so it should not be a surprise.

As Michael Mann, an atmospheric scientist at the Pennsylvania State University, says: “It isn’t a coincidence that we’ve seen the strongest hurricane in both hemispheres [western and eastern] within the last year.”

MORE POWERFUL

As the Atlantic Ocean continues to heat up, the trend is widely expected to be toward more powerful and wetter storms, so that Matthew might seem like pretty small beer when looked back on from the mid-century.

As with hurricanes, Pacific typhoons and the mid-latitude storms that periodically batter the UK and Europe are forecast to follow a similar pattern in an anthropogenically warmed world. Storm numbers might not rise, but there is likely to be an escalation in the frequency of the bigger storm systems, which tend to be the most destructive. An additional concern is that mid-latitude storms might become clustered, bringing the prospect of extended periods of damaging and disruptive winds. The jury is out on whether climate change will drive up the number of smaller, but potentially ruinous vortices of solid wind that make up tornadoes, although an apparent trend in the US toward more powerful storms has been blamed by some on a warming atmosphere.

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