Did Climate Change Cause Hurricane Irma, Harvey, Sandy or Katrina?

Fact: This is the wrong question to ask, since it assumes that one variable (in this case, climate change/global warming). In reality, multiple events led to hurricanes like Irma, Harvey, Sandy and Katrina, and increased ocean temperatures and atmospheric water vapor increased the strength of these hurricanes.

While there is no credible source claiming that climate change/global warming somehow “created” Hurricane Irma, what does seem to be in agreement is the idea that climate change, by resulting in more humidity and warmer oceans strengthens the impact of storms, resulting in more damage.

Dr. Meehl makes an analogy with baseball and steroids:

Think of it like this Dr. Meehl said: Barry Bonds had a certain average level of home run production in his baseball career before he started allegedly taking steroids. Once he started taking performance enhancers, his home run production increased, and he set the single season record for home runs in 2001. Now he holds the all-time record for the most home runs. If we watched Bonds hit any one of these home runs, would we be able to say that it was directly caused by his steroid use? “No, that’s impossible. But the odds of him hitting one are much higher; his base state has changed.”

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The 2007 IPCC report on Climate Change predicted this

Also, an increase in the amount of these super hurricanes WAS predicted in the 2007 IPCC report on Climate Change.

Based on a range of models, it is likely that future tropical cyclones (typhoons and hurricanes) will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical SSTs. There is less confidence in projections of a global decrease in numbers of tropical cyclones. The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than simulated by current models for that period./

Climate Change Denier Response

Climate deniers have responded with the straw man argument that “climate change didn’t cause hurricane Irma/Harvey.” This is a common straw man that assumes that a single variable must be responsible for an event. But of course, that’s not what climatologists are saying. These hurricanes would almost certainly have happened anyway. Global warming (by way of warmer ocean temperatures and a more humid atmosphere) were merely a steroid boost that strengthened these hurricanes.