Tropical cyclone intensity

Several colleagues and I have a new paper in Science about tropical cyclone intensity and climate change. The paper is behind a pay wall, sorry about that. However you can get the basic messages from my op-ed piece about it in the New York Times.

14 thoughts on “Tropical cyclone intensity

  1. The rise in global water vapor is reported everywhere, and I assume this is connected to storm severity. What I don’t understand is why NASA offer a supporting track of historic global humidity along with its global temperatures.

    • There are a number of global humidity data sets, but you are right that they are not publicized in the same way that temperature data are. The role of global water vapor in hurricane intensity is actually subtle, though – it’s not as simple as more water vapor = stronger hurricanes, though there are some scientists who have said it is. Increasing water vapor almost certainly does, however, increase the rainfall that hurricanes produce.

  2. In your op-ed, you said “…the physics says hurricanes should get stronger, because the tropical ocean surface heats up more than the atmosphere above it, increasing the temperature differential on which storms feed.”

    I haven’t read your paper, but that statement, as it stands, only holds true if the air temperature is lower than the water surface temperature. To the lay person, that sounds fanciful. Comments like this, from climate scientists, that directly contradict the daily experiences of regular people, are what fuel the climate-change denier movement.

    • Over tropical oceans where hurricanes form, it is absolutely the case that the air temperature is lower than the water surface temperature. You can look at the data, or measure it yourself (if you go out on a boat in a hurricane-prone part of the tropics). Or perhaps you are saying that, in order to avoid climate denial, scientists should poll “regular people” to find out what the temperature is, rather than measuring it with thermometers.

      • I’m saying don’t give the Sean Hannity’s of the world ammunition to shoot holes in your very important work. The Opinion section of the New York Times is not the same as a peer-reviewed journal. Know your audience, and be careful how you say things.

  3. With all the ice melting at the poles, is the temperature of the water actually warmer than usual?
    In the Bay Area/US, the temperature of the nearby ocean has not been higher.
    from a NON scientist!

  4. Cyclone activity in China is also down (see abstract below, published in J of Geophysical Research), which is not consistent with your comment – “In fact, other regions have not enjoyed the vacation that our most susceptible coastlines have had from serious storms. Ask the people in Taiwan and China, who just got hit by a supertyphoon named Nepartak (“supertyphoon” is, approximately, the western Pacific label for what we would call a major hurricane).”
    The climatology and trends of tropical cyclone (TC) high wind (TCHW; wind speeds ≥10.8 m s−1) in mainland China during 1959–2011 were studied based on a comprehensive series of surface wind observations from 574 stations. Of these stations, 41 were affected by TCHW more than once per year and were mainly located along the southeast coastline or at some inland mountain locations. The contribution of TCHW frequency to high wind (HW; wind speeds ≥10.8 m s−1) frequency was highest along the southeast coastline of China and decreased rapidly at inland locations. Both the TCHW frequency (intensity) and HW frequency (intensity) displayed significant downward (weakened) trends after the 1980s. The proportion of HW events accounted for by TCHW decreased, although the trend was not significant. The changes in TCHW frequency and intensity were associated with variations in the number of influencing TCs (ITC: a TC that causes at least one TCHW event), ITCTs (ITC time: an observation time with ITCs), the range of ITC influence, and ITC intensity and track. The annual number of ITCs and ITCTs declined consistently during the study period. The range of ITC influence as related to the TC size in 1983–2011 was smaller than in 1959–1982. The variation of the percentiles of ITC intensity showed an increasing (decreasing) trend of weaker (stronger) ITCs. Years with the maximum TCHW frequency had more ITCs and ITCTs than those with the minimum TCHW frequency.

  5. I was disappointed that in your NYTimes OpEd you did not mention the eastern Pacific cascade of hurricanes . Meanwhile, Nepartak made landfall at 160 mph; the western Pacific “supertyphoons run mostly at Category 5, though this one dropped to category 4, which is at the high end what we in the US regard as “major” hurricanes.

    People in the United States are so uninterested in international climate news, it would be a great service if experts like yourself pointed out that on our globe, we, the US, particularly the eastern seaboard, are not the whole picture.

    • I did make this broader point in the piece. Didn’t mention the east Pacific, but did point out that the Atlantic only accounts for around 10% (the actual figure is around 12%) of the average global number of tropical cyclones. I could also have mentioned that the northern hemisphere broke the record for category 4/5s last year by a lot – probably should have, in hindsight.

  6. Adam, a very compelling piece. Thank you for sharing and your very good work. All best, Coleen

    Coleen O’Shea Allen O’Shea Literary Agency 203.222.9004 (office) 203.984.2038 (cell)

    From: Adam Sobel <> Reply-To: Adam Sobel <> Date: Friday, July 15, 2016 at 11:13 AM To: Coleen O’Shea <> Subject: [New post] Tropical cyclone intensity

    Adam Sobel posted: “Several colleagues and I have a new paper in Science about tropical cyclone intensity and climate change. The paper is behind a pay wall, sorry about that. However you can get the basic messages from my op-ed piece about it in the New York Times.”

  7. Thank you for a fine article. I must, however, take issue with one paragraph. You say “…the physics says hurricanes should get stronger… The best computer models also predict stronger storms, so we have separate but consistent lines of evidence”. The problem here is that the computer models are of course based on the same physics, and so these are effectively one and the same line of evidence.

    On the slightly different topic of fewer storms but stronger ones, I wonder if anyone has tried to measure the total energy dissipated by the storms on average. And does this total energy increase in a way that tries to match the excess energy from global warming? Our planet is amazingly self-regulating, thanks mostly to vast oceans of water. Hurricanes are a great way to shed excess energy.

    • About your first point, not so, though an understandable interpretation of what I wrote, which had to leave out a lot due to space. What I mean by “physics” is calculations of potential intensity, which is what our Science article is about. Basically this is a physical theory (which has been tested in a number of different ways) that tells us how strong a hurricane can get for a given environment, even without a storm being present. By “models’ I mean models which actually simulate storms, and don’t use the theory of potential intensity. True, both are based on the laws of physics, but in different ways and with different approximations.

      On the second topic, the kinetic energy dissipated in hurricanes is very, very small compared to the total thermal energy in the atmosphere, and research which has tried to look for a critical role for hurricanes in regulating the climate have not been successful in my view. This question has not been studied that much, but I think the evidence so far suggests that the climate would be fine either without hurricanes, or with a lot more hurricanes – in other words they do what they do for their own reasons and not because the climate as a whole needs them to.

  8. Adam
    Every point of credible reference such as NOAA clearly states that the reason for hurricane formation is unknown. Ocean suface temperatures play a part but the real reason is still ellusive. How can you predict that hurricanes will become stronger, but dont know when, but state that because of so called CO2 etc global warming it will happen.
    Thank you

    • I don’t know where you are getting the information to justify your first sentence, but it’s an extreme overstatement of the uncertainties. We know quite a lot about hurricane formation. It’s true that we don’t know everything, as I alluded to the op-ed. But there is a large scientific literature on it and we understand many of the factors involved. The National Hurricane Center now issues forecasts of hurricane formation up to 5 days in advance and they are pretty good – and the models they use are essentially the same as the ones I wrote about in the Times.

      We understand hurricane intensity still better. That is, once a hurricane forms, we have a pretty deep understanding of the maximum strength it can achieve.

      Here’s an analogy. Imagine putting a teacup at the edge of a table in a house with kids running around. You may not be able to predict when it will fall or which kid will knock it over, and if you line up a bunch of cups on the table you probably can’t predict how many will have fallen by the end of the day. But you have a pretty good idea of what the process is by which any given cup is fairly likely to fall sooner or later, and you know very well how far it can fall once it does (the floor).

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