BPSDB The recent tornadoes in the United States have lead to a resurgence of articles talking about the link between extreme weather, natural disasters and climate change. If you are an interested member of the general public you are undoubtedly confused as the two sides of the debate seem to be making opposing claims, and both seem to have some science to back them up.
I’d like to talk a bit about why there is this confusion and what it means in practical terms for you and me. Then I’d like to discuss the opinion of the folks who take this issue very seriously indeed. No, I don’t mean the scientists, much more seriously than that – I am referring to the insurance industry.
The critical phrase is “seem to be making opposing claims“, because for the most part they are not. The climate change Deniers erroneously characterize the science based reports as ascribing the various tornadoes, storms and what have you as being caused by or linked to climate change. That is not what the ones I sampled were actually saying.
If you read the various reports they correctly note that given the current state of our knowledge it is impossible to directly link the recent extreme weather to climate change. It is also impossible to definitively say there is no link; that’s how uncertainty works.
Now from what I can gather it is probable that the influence of climate change on the most recent spate of tornadoes in the US south west was very small to none, but that’s not the end of the story.
In this case the problem boils down to the fact of our incomplete knowledge of many 
complex and interacting systems. Tornadoes are determined to a large extent by atmospheric moisture content and wind shear. Climate change is causing the former to increase and the latter to decrease. How fast and by how much each will change, particularly on a regional scale, is anyone’s guess.
The recent tornadoes are being ascribed more to the effects of the La Nina/El Nino natural cycles than anything else, but these simply refer to differences in ocean surface temperature. Stating the obvious, ocean temperature is most definitely being affected by climate change. Exactly how, and what the consequences will be are less well understood,
The oceans are not static; they are dynamic systems with complex currents and cycles that range from the tides to oscillation patterns with periods from years to decades. These are influenced primarily by water temperature and salinity, both of which are changing as a consequence of climate change. As one “natural” cycle changes it also influences the others, and so on.
Now add to that the uncertainties about climate change. In this case the biggest uncertainty is what humans are going to do about it and when. Based on current policies and actions the most likely answer is “far too little, way too late.” That being said, it’s not just a matter of how much the climate changes, but also how fast.
Most of the changes in temperature etc that we see discussed relate to the coming century. That is most definitely not because climate change then plateaus or stops. If we do nothing we face a catastrophic 21st century; after that things start to get really bad.
Be that as it may, a scientist cannot give a single answer to what extreme weather is going to be like in 30 or 50 yrs if you can’t tell her what our CO2 emissions are going to be over the next 30 or 50 yrs. Without that information all she can do is give a range of possibilities from the highest to lowest possible scenarios, with the added uncertainty of our incomplete understanding of these complex systems.
Scott Mandia on the recent swarm of tornadoes, flooding, and extreme precipitation events
Hat tip to Climate Change: The Next Generation
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