Fact Check: Is Climate Change Causing More Frequent Or Severe Hurricanes?

Every year at this time, when hurricane season rolls around, corporate media starts pumping out headlines linking the severity of hurricanes to climate change. [links, emphasis added[

But is there causation or correlation? And if changes in the climate do affect hurricanes, is it in the way climate activists claim?

Climatologist David Legates says, “[If] we have colder periods, we will get more hurricane activity. If we have warmer periods, the hurricane activity tends to drop off.”

Legates serves as a visiting fellow for the Science Advisory Committee in the Center for Energy, Climate, and Environment at The Heritage Foundation, and is a professor emeritus at the University of Delaware. He is also the co-author of the book “Climate and Energy: The Case for Realism.”

Virginia Allen: It’s my privilege today to welcome back to the Daily Signal Podcast, climate expert and Professor David Legates. Thank you so much for being back with us.

David Legates: It’s a pleasure to be back. Thank you.

Allen: Well, I’m excited to talk about hurricane season and climate change. I was looking at some of the big headlines because it always feels like this time of year we start hearing a lot in the news about the connection between climate change and hurricanes. Hurricane season technically starts at the beginning of June and runs through November.

So this was a headline from NPR last March. They say “Sequential Hurricanes Are Becoming More Common Because of Climate Change.” A CNN headline from April 2022 reads “The Climate Crisis is Supercharging Rainfall in Hurricanes, Scientists Report.” NBC News just recently ran a headline, “Category 6? Climate Boosted Hurricanes Pushed Scientists to Rethink Classifications.”

Professor Ligates, are hurricanes over the past five to 10 years more severe than hurricanes were maybe 50 or 100 years ago?

Legates: Of course, they are because these sites could never tell you anything that can’t be true. See, when you say more severe, we can parse that in a variety of ways. We can say there [are] more hurricanes happening.

We can say that the hurricanes that happen are becoming more intense. We can say that the hurricanes that are happening are actually becoming larger and more powerful overall. Or we can say that they’re making landfall more often than not. And after all, a landfall hurricane is the worst-case scenario. If a big hurricane stays out in the Atlantic, that’s only a good thing unless you’re a shipper. So we can look through each one of these in steps and I’ll give you some slides that you can see.

This [the below image] is by Ryan Maue. He and I worked at NOAA [National Oceanic and Atmospheric Administration] together. He was the NOAA’s chief scientist and he’s put this together from data from NOAA. And if you look at from 1971, when we started to … see things by satellites, because a lot of the Central Atlantic was missing, if you will, when we didn’t have satellites to see out there on a regular basis, ships tend not to want to sail through tropical storms and hurricanes.

As you can imagine, if you look at that record, you see lots of variability over the years, but you see no long-term trend either in tropical storms or hurricanes. So we can’t really say that over the last 50 years that there’s been a dramatic increase in the number of tropical storms or hurricanes or has there been a drastic decrease. It looks just like there’s lots of variability, which we call year to year. Some years we get hit and some years we don’t. And so there’s no change there.

Well, maybe the ones that are occurring are becoming more intense. So we can also look at what we call major hurricanes. These are hurricanes with wind speeds that exceed a hundred knots. And when we look at that compared to all hurricanes, again, we see lots of variability but no long-term trend.

And in fact, if we look at the record closely, about a year or so ago, we were at an all-time low in terms of major hurricanes on the planet, which is kind of interesting if you are told constantly we’re seeing more of these are becoming bigger, you would expect more major hurricanes, not much less.

The third argument is, well, maybe we have the same number and the same intensity, but they’re getting bigger in size, hence they’ve got more energy. And we measure that through something called the accumulated cyclone energy index or ACE index.

And what that does is just take all the energy of all the storms based upon their size and their wind speed, average them together, come up with an index, and we look at time changes. And if you look at that from, again, from about 1972 to the present over about 50 years, you see lots of variability. You see the mid-nineties had lots of ACE, if you will. There was a lot of energy. It peaked again in the mid-aughts or whatever we call those and peaks again in the late teens.

But there is no long-term trend. It goes up and down and up and down and up and down, but never trends in either direction.

The final one that I postulated was maybe we’re seeing more landfalling hurricanes. And the interesting thing is this is the first signal we actually see it’s data from Roger Pike Jr.

Looking at total North Atlantic and Western Pacific Hurricane Landfalls from 1945 to 1921. And when you look at total hurricane landfalls, they’re actually decreasing, which says in a sense that hurricanes are staying away from the coast more.

There was a lot of activity of landfall in hurricanes in the 1950s and early 1960s, which was an active period. But there’s your trend, and so if you have anything you want to write home about, it’s that landfall hurricanes are decreasing in intensity or increasing in number over the last 50 years, which is quite opposite to what you saw on CNN and New York Times and Washington Post, all those.

Allen: So we’re seeing a decrease in the number that are making landfall?

Legates: Yes, it is less that are making landfall, which should be a good thing to write home about. I know news likes to say, let’s pick on the bad stuff. If it bleeds, it leads, but this is good news to write home about: that if there’s something in that signal, it’s a good signal.

Allen: That is a good signal. Now, we have spoken before on this podcast about how there [are] natural cycles on the planet of warming and cooling. Do those cycles affect hurricanes?

Legates: Actually, they do. There have been a number of studies done.

I think there was a study in 2001 by Boost that looked at, looked at, yeah, landfalling hurricanes going back to 1600. And in particular, what that group found was from 1600 to 2000 in New England. This is Peterson, Massachusetts, Providence, Rhode Island, an area that from that 400-year period, the most active period was the 19th century.

And I’ll ask the question rhetorically, what was the coldest period between 1600 and 2000? And the answer of course is the 19th century. Same research was done by Kerry Mock at the University of South Carolina. He did tropical cyclones impacting Charleston from 1778 to 1998.

The most active period in Charleston was the 19th century, which happened to be the coldest. And then a colleague of mine at LSU Kalu did some research in southern China, and he wrote remarkably, the two periods of typhoon strikes in Guangdong coincide with two of the coldest and driest periods in northern and central China. So the take-home message here is that essentially if we have colder periods, we will get more hurricane activity.

If we have warmer periods, the hurricane activity tends to drop off. The next question you’re going to ask me is why does that happen?

Allen: Why does it happen? And the message that we hear from the media is the opposite. They say that because the planet is getting warmer, we’re seeing more hurricanes. But you say the opposite is true.

Legates: It’s exactly the opposite. Very good question.

So what happens is why do we get a hurricane? Essentially we have what we call an equator-to-pole temperature gradient. The equator is warm, the poles are cold, and so therefore we need to move energy from the equator to the pole. We do that in three ways. We do that through the motion of the atmosphere. So we get westerlies for example, which is why our storms tend to move across the United States from west to east. We get easterlies in the tropics and easterlies in the polar region.

Second, we get oceanic circulation, so we get what are called gyres or circular types of circulation that exist in the oceans. And the third is by moving what we call latent heat, which is just a fancy way of saying evaporate water store energy, move it somewhere else, condense that moisture, and get the energy back.

And hurricanes are very useful at doing that. They pick up a lot of water and a lot of energy from the tropics. They move forward and they drop it off. So the stronger the pole trade or temperature gradating you have, the more conflict you’re going to get and the more need there is to move energy forward. I often ask what drives the tornadoes.

For example, in the spring, the answer is you’ve got really cold dry air coming out of Canada and it’s colliding with really warm, moist air in the Gulf of Mexico. And so when you get these two contrasts come together, you get a lot of storminess. Imagine a world where the pole and the equator are exactly the same temperature. If they’re at exactly the same temperature, you’re not going to get that contrast. You’re not going to get the storminess, you’re not going to get hurricanes at all because there’s no reason to produce them there.

Storminess is going to be much reduced. So the argument is a warmer world would be a less stormy world because in a warmer world, you warm the tropics but not much. It’s already very warm and you’ve got a lot of water. Water takes a lot of energy to warm, so you get very little warming in the tropics, but you get lots of warming in the polar regions, the polar regions are drier, so you don’t have lots of water.

The polar regions are colder, so it’s easier to warm the temperature. Polar regions are covered with ice. You melt that ice, you release land underneath that’s darker. You absorb more energy causing more rising temperatures. Y

ou have sea ice up there that covers the surface keeping literally the warmer water from the colder air, sea ice melts. You get more energy coming up from the ocean. There [are] a variety of other reasons, but when the world warms the pole warms more than the equator, so the equator-to-pole temperature gradient decreases, and you get less need for severe storms and that includes hurricanes.

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