Extreme Weather and Climate Change

A long-standing pet-peeve of mine is the way that, in the endless tug-of-war in the media and blogosphere over climate change, both sides try to score cheap points by pointing to isolated extreme weather events as evidence for or against the phenomenon.  “Ha, there were several big blizzards this winter!  Global warming my foot!”  “No, actually more blizzards is evidence of global warming, believe it or not!”  Extreme events like Hurricane Katrina or the Great Russian Heat Wave are waved as poster-children for the dangers of climate change, so right-wingers gleefully poke holes in the science of attempted attribution.  You may recall that I posted on this subject, with particular reference to hurricanes, a few months ago.

Ricky Rood over at Weather Underground, the source for the best weather blogs around, has posted an excellent essay on the “Perils and Pitfalls of Event Attribution.”  Although personally convinced of the reality and seriousness of climate change, Rood argues that the tendency of some climate scientists and the media to focus on individual extreme events and attribute them to climate change is counterproductive, bad science, and indeed impossible by definition.  It reduces this crucial public discussion to cheap sound bytes and blaring headlines, drawing attention away from substantive verifiable claims:

“It is hard to see how playing the game of defining extreme events and then attributing that event to “climate change” can ever be won. In fact, it seems like it is a game that necessarily leads to controversy, and controversy is the fuel of talk radio, blogs propagating around the world, and the maintenance of doubt.”  

The essay is well worth reading for weather buffs or environmental ethics buffs (yep, I’m talking to you, Byron. ;-))


Hurricanes in a Warming World

Eh, what the heck…I’ll come out of the closet and spice up this theology-heavy blog.

As I recently posted on my old blog (which I falsely predicted would be resurrecting), the much-touted link between climate change and more frequent and more intense hurricane turns out to be much trickier than you would think.  The catastrophic and hyperactive 2004 and 2005 Atlantic hurricane seasons naturally led people to fish about for an explanation for the chaos, and it wasn’t hard to find a few scientists ready to line up and point the finger at global warming.  It stood to reason, of course, that if hurricanes fed on warm ocean water, and the world was getting warmer, including the oceans, then hurricanes would get more numerous and stronger.  At least, that was the bastardized form of the argument that was repeated often enough in the media to become accepted fact.  The actual scientists recognized that other factors would come into play and the relevant papers generally projected an actual decrease in number of tropical cyclones, with a slight increase in average intensity, and a marked increase in maximum potential intensity (which depends largely on water temperatures).  

This summer, other possible complicating factors emerged, as I discussed in that old post.  Coming into this season, projections were for a hyperactive Atlantic hurricane season–one of the most active on record.  What materialized instead from June 1st to August 20th was almost complete inactivity–sure, Alex spun up into the second most intense June hurricane recorded on June 30th, but after that, there were only two feeble and short-lived tropical storms, Bonnie and Colin.  Most remarkably, this inactivity coincided with well below-average eastern Pacific activity and historically low western Pacific activity, so that, on the whole, the Northern hemisphere was on track for record lows.  

Now, what else was going on at this time?  Well, much of the planet, particularly Asia, was baking–in eastern Europe’s case, under temperatures without equal in the historical record.  It was theorized that the super-heated landmasses caused a pattern of sinking air over the oceans, reducing atmospheric instability and putting a lid on cyclone development.  So global warming might actually suppress cyclone development?  Sure enough, no sooner did the Great Russian Heat Wave break in mid-August than the Atlantic saw a period of truly remarkable hurricane activity, producing over the next four weeks 9 named storms and five hurricanes–all five of them major hurricanes and four of them Category 4s–and breaking or challenging several interesting records in the process (for more on these, see below).  This pushed Atlantic hurricane activity from half the normal to date on August 20 to double the normal to date on September 20.

However, this shift did not occur in the Pacific Ocean, which remains at the lowest levels in the 30-year data period, thus the heat wave correlation thesis may not work so neatly after all.  The inactivity in the Pacific basin indeed is so pronounced that it seriously calls into question the thesis about climate change and hurricane activity.  See, while Atlantic hurricane activity gets much more press than cyclones in the rest of the world (for obvious reasons), it in fact only comprises only about 1/10 of global tropical cyclone activity on average.  And if the whole planet (more or less) is warming, and a warming planet means more cyclones, then it should mean more cyclones the world over.  But in fact, global tropical cyclone activity has collapsed in half since 2005, and has been sitting for a couple years now at record lows (with the records again going back 30 years)–and the highest years were back in the mid-90s. 

Why do we in the Anglo-American world labor under the delusion that we are living in a time of dangerously active and ever-worsening hurricane seasons?   Simply because the North Atlantic is in the midst of one of its well-documented twenty-year cycles of elevated activity–meanwhile, the rest of the world enjoys relative placidity.  So let’s hear the end of this careless pseudo-science, until there’s data to support it.

 

Of course, it’s not that simple either–it never is.  While these statistics are based on Accumulated Cyclone Energy measurements, probably the best way of comparing overall cyclone activity (and which does take intensity into account), they hide the curious fact that most of the cyclone basins in the world have recorded their most powerful storms on record in the past few years.  Other apparent anomalies have emerged that provide plenty more grist for the mill of those pushing hyping the effects of climate change on hurricanes.  In the Atlantic, at least, we have seen in recent years several records fall for speed of intensification, which is perhaps the scariest kind of record to be broken, and more and more storms seem to be pushing the envelope of what were thought to be plausible intensification rates.  Likewise, we have seen storms forming and strengthening in parts of the ocean unaccustomed to strong hurricanes.  Just in the past week, for instance, we had by far the furthest east Category 4 on record (Hurricane Julia), the first ever major hurricane in the Bay of Campeche (Hurricane Karl), and Hurricane Igor slammed into Newfoundland as its worst-ever hurricane, not to mention capturing the record for the largest Atlantic hurricane ever (in size).  Are these proof that something scary is happening over our oceans as a result of climate change, something that may make these already enigmatic storms even more unpredictable?  Or does this just mean that we don’t have enough data yet to accurately understand and compare what’s going on?  

Whichever is the case, science needs to be just a bit more humble in the claims it makes about these mysterious monsters.