Hurricane Havoc: can we really blame climate change?
Two main opinions laced social media comment threads (a place I don’t recommend).
1) We call it ‘hurricane season’ for a reason and it’s happened for centuries.
2) These hurricanes are a direct result of climate change.
Don’t be too quick to scoff at the denialist tone of opinion 1, there is merit to that argument.
The 1935 “Labor Day” hurricane holds the record for lowest central pressure in a hurricane making landfall. Irma is equal 6th and Harvey doesn’t even make the top 10. The lower the pressure at the centre of the storm, the more intense it is. Hurricane Allen, 1980, holds the record for strongest winds. Hurricane “Cuba” remained a category 5 hurricane the longest (3 days, 6 hours) in 1932 followed by Irma (3 days, 3 hours).
Is this year’s hurricane season a preview of what to expect in a warmer climate, or are we blaming climate change for natural processes?
There is a whole branch of science, called climate change attribution, which tries to answer this question.
An experiment to test if hurricanes Irma and Harvey were caused by climate change would go like this:
Run a model of the Atlantic Hurricane season for thousands of years and count the number of hurricanes with similar characteristics to Harvey and Irma.
See if you get the same number
The point of the experiment is to see whether more Harvey and Irma-like hurricanes form in the model that replicates a warmer world. If yes, we can say climate change is making hurricanes more dangerous.
Easier said than done…
Climate change attribution experiments are simple when there is only one variable and it can be measured everyday like temperature. Hurricanes are more complicated.
First, there isn’t a hurricane on every single day, so one thousand years of data may only produce a few hundred hurricanes.
Second, not all hurricanes are the same.
Hurricane Katrina was only a category 3 when it hit New Orleans and caused 1,836 deaths, while Hurricane Jose was a category 4 and didn’t kill anyone, so how can we classify a “dangerous” hurricane-especially a modelled hurricane that doesn’t really exist. Because hurricanes are far less frequent than a temperature measurement, it is difficult to separate the climate change signal (if there is one) from the noise.
Imagine a violinist performing a song you’ve heard one thousand times and they get a note wrong. You would definitely notice. Now, imagine the Australian Symphony Orchestra performing a song you’ve only heard a couple of times and one lone violinist messes up a note. Unless you’re the embarrassed violinist, you probably wouldn’t notice. The same idea applies to climate attribution. If there is only one variable (temperature) and thousands of years of data, it’s easy to notice notes that are out of place. But, if there are multiple variables, you would need to have heard the song hundreds of thousands of times in order to notice a mistake.
I spoke to Dr. Andrew King, a climate scientist from the University of Melbourne, he explained, while we can’t know for sure whether climate change caused an individual hurricane, we do know “impacts like heavy rain and flooding are exacerbated in a warmer world.” We can’t perform a climate change attribution experiment for Hurricanes Harvey or Irma, but we can for their effects. Climate change may have caused Harvey to pause over Houston and dump gallons of water on the city. A warmer atmosphere can hold more water (that’s why it’s so humid in South-East Asia); 3% more moisture for every 0.5C of warming. This relationship likely contributed to Harvey’s flooding. As for Irma, rising sea-levels enhance storm surges-one of the deadliest aspects of a hurricane.
Huge hurricanes have been wreaking havoc for centuries, but climate change may make them worse.