Has Global Warming Already Been Affecting Our Hurricane Season?

A video created by 350.org has been circulating around the web recently discussing a proposed change to how we name hurricanes:

First things first: yes, I chuckled at the video, and some of the lines are pretty hilarious (‘Rick Perry: The Tragedy’ headline, in particular).  But I think the widespread propagation of this video brings up a bigger issue: can we truly attribute hurricane activity over the past several years and in the recent years to come to anthropogenic climate change?  This is a crucial point, because, if we can’t show this connection between human-induced changes and hurricane activity, then this media campaign by 350.org only adds fuel to the current conservative dialogue of climate change hoaxes and misrepresentation of information.  Yes, we need an influential media presence to continue to educate the public about the realities of what we are doing to our planet and atmosphere, but our rallying cry must lie in fact, scientific method, and evidence.  These are the pillars of our stance, and we cannot abandon them for the sake of sensationalism.

So what do the facts say about this?  A great resource is this website hosted by the Geophysical Fluid Dynamics Laboratory located in Princeton, NJ and written by Thomas Knutson.    Included here is a quick summary of the large amount of information presented there, so I encourage you to check out the website on your own to learn more.

The key findings they discuss:

PRESENT: We do not have enough information yet and our models are not accurate yet to confidently conclude that human activities and greenhouse gas emissions have affected current hurricane activity.

FUTURE:  That being said, our models do predict an increase in hurricane activity (a 2-11% increase) by the end of the 21st century.  So, our current actions and emissions WILL affect hurricane activity at an observable level, just not yet.  This is due to the complicated feedback loops between the atmosphere and water, in which chemicals we emit to the atmosphere now will only show effects years down the road.

INTENSITY: Anthropogenic climate change will increase the intensity of the storms by the end of the current century, in terms of both winds and rainfall rates.

Below is a figure from the report linked above showing the relationship betwen Atlantic surface ocean temperatures and the Power Dissipation Index (PDI) of hurricanes during the summer season of each year.  The PDI is a combined measure of frequency, duration, and intensity of hurricanes.

So, as the blue lines rises, sea temperatures are going up, and as the green line rises, hurricane ferocity is increasing.  You can see a clear correlation between the two measures – and we know that human greenhouse gas emissions increase sea temperatures.  This appears to provide a clear prediction of more frequent, more intense hurricanes.

There are some details regarding this data and some other recent publications that make the interpretation a little more complicated, so I again encourage you to skim the link given above.  But this is the basic idea.  No, current hurricane activity is not likely linked to our greenhouse gas emission, but it is EXTREMELY likely that future hurricanes will be, and the results will be more damaging, more frequent storms.  I believe this point is important to make clear as we as a society begin discussing propaganda such as 350.org’s movie.  I am all for educating the public and taking all actions necessary to promote the idea that climate change is real and we are the cause behind its rapid pace.  But we must do so in a scientific, honest way that maintains the integrity that is the backbone of our fight.

References

Knudson, Thomas. ‘Global Warming and Hurricanes.’ http://www.gfdl.noaa.gov/global-warming-and-hurricanes. Sept 1, 2013.

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