Climate change is making hurricanes more destructive

A lot of people don't want you to understand this

yes, it’s in the southern hemisphere

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Because hurricanes are one of the big-ticket weather disasters that humanity has to face, climate misinformers spend a lot of effort muddying the waters on whether climate change is making hurricanes more damaging.

With the official start to the 2023 hurricane season in the North Atlantic on June 1, I figured it was time to explain why we can be so confident that hurricanes are indeed more destructive today due to climate change.

Note: from here on out, I’ll refer to hurricanes as tropical cyclones (often abbreviated as TCs), which is a more general term for this type of storm.

1. Tropical cyclones are becoming more destructive: sea level

Even if tropical cyclones are not changing because of climate change (which is very unlikely, see below), sea level is higher, so today’s TCs do more damage than an identical tropical cyclone a few decades ago because the storm surge is riding on a higher sea level.

As Prof. Adam Sobel said in Congressional testimony:

The most certain way in which hurricane risk is increasing due to climate is that,
because of sea level rise, coastal flooding due to hurricane storm surge is becoming
worse. Storm surge occurs when the winds from a storm push the ocean onto the
land. The total flooding is determined by the surge (the part produced by the wind),
the tide, and the background average sea level. As sea level has risen … the flooding is exacerbated by that amount.

Climate misinformers will respond that sea level only contributes a few percent to the total flood depth. But the non-linearity of flood damages means that even a small contribution from sea level rise to total flood depth can increase damages a lot.

the sea is coming for you

For example, in 2011, Hurricane Irene hit the New York region with a storm surge of around 1.5 meters; existing flood infrastructure was able to handle that and there was little damage.  Just a year later, Hurricane Sandy hit the New York region with 2.75 meters of storm surge, overwhelming flood infrastructure and leading to damages of $62B. 

This is classic non-linearity, where you get zero damage until a threshold is passed (somewhere between 1.5 and 2.75 m) and then damages increase exponentially.

It has been estimated that sea level rise due to global warming increased Sandy’s total flood depth by 0.1 meters and this increased the damage from the storm surge by $8B.  Thus, the last 4% of the total flood depth generated 13% of the total damage. 

Bottom line: Because of sea level rise, you can say with 100% certainty that climate change is making every TC more destructive.

2. Tropical cyclones are becoming more destructive: rainfall

Climate change will increase TCs’ rainfall intensity due to the following logic chain: 1) most of the water vapor in air flowing into a tropical cyclone’s core will fall out as rain when the air ascends in one of the rain bands, 2) in a warmer climate, the air flowing into a tropical cyclone’s core holds more water vapor. Put points 1 and 2 together and you get more intense rainfall!

Flooding in Houston after Harvey

That’s it. You don’t need any fancy physics to understand why we’re so confident that tropical cyclones will produce more rain as the climate warms. In fact, the IPCC says that we are already seeing this¹:

There is high confidence that anthropogenic climate change contributed to extreme rainfall amounts during Hurricane Harvey (2017) and other intense TCs.

They also say it’s going to get worse as the climate continues to warm.

Bottom line: You can be confident that TCs are already producing more rain due to climate change, and this is another way they are increasingly destructive.

3. Tropical cyclones are becoming more destructive: intensity

Palm trees don’t enjoy this wind

Basic physics tells us that hurricanes get more intense as the climate warms. Climate models reproduce this result and observations also show evidence of strengthening TCs. The IPCC says we’re already seeing this²:

It is likely that the global proportion of Category 3–5 tropical cyclone instances … have increased globally over the past 40 years.

and this will continue in the future³:

the proportion of Category 4–5 TCs will very likely increase globally with warming.

Bottom line: You can say with some certainty that TCs are on average more intense than those that form in a cooler climate.

4. What we’re not sure about: number of tropical cyclones

We don’t have a good handle on what determines how many TCs form annually. Every year there are around 100 of these storms globally, and we don’t know why it’s that number and not, say, 10 or 1000. Without a basic theory, we have little confidence in how the number of TCs will change as the climate warms, although most models predict that the number of TCs will decline.

Bottom line: When talking about damage over an entire season, it is good news if TC numbers actually decline (remember that we have very low confidence in this prediction).

But in most cases we’re talking about the damage from a particular TC, so this is irrelevant. That TC already formed. And that TC is more intense, rainier, and riding on a higher sea than it would be in a world without climate change.

5. What we’re not sure about: monetary damage from tropical cyclones

Every climate misinformer loves loves loves to talk about how, there’s no trend in the observed (normalized) damage. I could explain why this is wrong, but Prof. Kerry Emanuel already did it and you should just read what he wrote.

Another reliable yardstick is to ask the people who have money on the line: insurance companies. If you do that, the verdict is clear: insurance premiums are skyrocketing and companies are fleeing places that are vulnerable to TCs (Florida, Louisiana) — exactly what you would expect in a world where the risk of TC damage was going up.

Sucks to be them

Bottom line: The “no increase in damages” is not a very good argument for the many reasons that Emanuel explained. It deserves to be dropped into the dustbin of history, but it’s so useful to climate misinformers that I’m sure it will never disappear.

Summary

This post has only touched on the ways that TCs are getting more damaging. There are even more ways, such as changes in the tracks of TCs moving to higher latitudes, more frequent rapid intensification, or the slowdown of TC translation speed, all of which can also increase destructiveness.

When arguing against this, climate misinformers don’t necessarily propagate outright lies. Rather, their method of misinformation lies in the selective emphasis of certain facts that bolster their stance. For example, they will focus on statistics like the number of storms, emphasizing that we don’t see any increase while conveniently omitting that climate scientists don’t predict an increase.

And they fail to acknowledge the actual factors that are driving destructiveness, such as the increase of storm surge damage caused by sea level rise or the fundamental physics that tells us that TCs will produce more rain as the climate warms. This is classic cherry picking.

Instead of the selective offering of climate misinformers, you should look at all of the data. If you do that, it’s clear that hurricanes and other TCs are getting more destructive.

1. IPCC Sixth Assessment Report, Working Group 1, Section 11.7.1.4.

2. ibid, Section 11.7.1.2.

3. ibid, Section 11.7.1.5