Thread by @AndrewDessler

If you hear a "reasonable middle bro" who "cares deeply about the environment" but tells you that "climate change is not making hurricanes worse," they're gas-lighting you.

Let's examine the peer-reviewed science on this issue. From chapter 6 of the IPCC Ocean and Cryosphere report.

See also this web page from NOAA:
gfdl.noaa.gov/global-warming…

First, rainfall. There is a good reason for rainfall to increase with warming: Warmer sea surface temperatures leads to more water vapor in the boundary layer. Unless convergence into the storm DECREASES, you'll get more rainfall.

Here's what NOAA says:

Next, intensity: Yes, we project hurricane intensity to increase with temperature:

It's possible that the total number of storms will decrease. However, the vast majority of hurricane damage comes from the strongest storms. Thus, the shift to stronger storms, even if total cyclone numbers decline, means that total damage can skyrocket.

Kerry Emanuel sent me some figures to show this (reproduced with his permission) & I've paraphrased his comments.

Model-simulated probability density of annual U.S. hurricane damage, plotted on log damage scale, for the climate of late 20th century and late 21st century.

Owing to a projected decrease in total storm frequency, there is a decline near the peak of the probability curve, but notice also an increase in the far tail of the distribution. This is consistent with the IPCC's statement of reduced frequency and increased intensity.

But we will see just how misleading statements like this are in this graphic, that shows the product of the damage and the probability graphed against log damage ... when integrated, the areas under the curves represent that total expected damage.

Here we see that the decline in total number of hurricanes is completely irrelevant. Virtually all the increased damages comes from changes in the tail of the distribution. /end of Kerry's comments

Finally, storm surge. Sea levels are going up, which is primarily caused by global warming. This is making storm surge worse.

What NOAA says:

So don't fall for climate inactivist shysters peddling the claim that climate change is not contributing to these disasters. They are just another type of climate denier.

tl;dr summary scorecard:

climate change is causing:
increased storm surge — 100% certain
increased rainfall — IPCC says "likely" but I think it's nearly 100% certain
increased intensity — likely

A few more points have occurred to me. The "reasonable denier" will say, "But observations don't show hurricanes getting stronger." You know you've heard them say that.

That's a true statement. We don’t have very good measurements of hurricanes, so it’s hard to confidently estimate trends from data (e.g., the Atlantic is the only basin where we routinely fly planes into the storms and they’re only about 12% of global TCs).

We do, however, have some evidence that they’re getting more intense (e.g., myweb.fsu.edu/jelsner/strong…). But the main reason scientists are so confident that hurricanes will get more intense with warming is because of a little thing called physics.

This is one of the classic papers: nature.com/articles/44326

Either you believe physics or you don't. If you do, then you'll have a reasonable level of confidence that hurricanes will indeed get stronger — even if we cannot yet detect it in the data.