Dear Science,

It seems like more hurricanes over the past few years have been monsters. If I understand things correctly, water and heat spell hurricane. Does that mean global warming will give us more monster storms? If I'm not mistaken, even a couple degrees warmer means more massive hurricanes, because that's more heat that has to dissipate.

Weathered

The question you're asking is fundamentally difficult to answer—to the delight of oil plutocrats worldwide. We can't exactly raise or cool global ocean temperatures, undo or redo global warming at whim, in an effort to test if climate change causes hurricanes to become more powerful. As rational people, we're stuck with looking for inferences, clues, and mechanisms to answer your question.

Let's start where you started, by considering what happens when the oceans warm up. We can measure how average ocean temperatures—particularly in the Gulf of Mexico and the Caribbean, where hurricanes gain their strength—have gone up in tight correlation with the total amount of carbon released by humans into the atmosphere. This added heat represents an enormous amount of energy. We can also directly correlate the amount of heat in the water below a hurricane with the probability a given hurricane will get stronger. By rolling all of this mechanistic thinking into mathematical models, we can predict that as carbon dioxide goes up, surface water temperatures go up, and the average strength of a hurricane will go up as well.

Next we can look at historic data. Over time, hurricanes have become somewhat stronger on average. These aren't subtle shifts; the differences in strength here are difficult to comprehend. The energy required to make the rain in a (single) typical hurricane is roughly equivalent to 200 times all the energy consumed by all human beings in a given year. Generating the wind (perhaps surprisingly to many) is much less energy—about half the energy produced by all electrical plants everywhere on the planet. The amount of extra energy contained in the oceans, as average water temperatures have crept up over the past few decades, dwarfs these numbers. Since 1970, there haven't been more hurricanes (on average) per year. But the average strength per storm—how much energy in rain and wind it consumes and releases—has steadily gone up, right as water temperatures have gone up with carbon dioxide levels.

We can measure how water temperatures in the ocean have gone up as carbon release by humans has gone up. We can show that hurricanes get stronger over warm water. Hurricanes are stronger than before. Can science prove to you that human consumption of fossil fuels is causing stronger hurricanes? It depends if this chain of logic convinces you. If not, go around trying to convince people to stop using all fossil fuels for a decade or so. Then we'll know for certain.

Logically yours,

Science

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