Cut thru the myths about Irma, Harvey, and climate change

Summary: Climate scientist Judith Curry discusses Hurricanes Harvey and Irma, the state of knowledge about hurricanes, and the announcements of their connection to climate change. These storms teach us lessons we cannot afford to ignore.

Hurricane Irma
Geocolor image of Hurricane Irma by GOES-16 satellite on 8 Sept 2017. NOAA/CIRA.

Interview of Dr. Judith Curry
by David Whitehouse of the Global Warming Policy Foundation.

Discussing Hurricane Harvey, Hurricane Irma, and climate change.
15 September 2017.

Here is the transcript. Video of the interview is at the end.

DW:  First of all – do we understand hurricanes?

JC:  We’re getting a whole lot better at predicting individual storms. This has really been a banner year for long range prediction, and detailed prediction for hurricane impacts. Models like ECMWF {European Centre for Medium-Range Weather Forecasts} and the NOAA models – they’re doing a good job. We understand the basics of how hurricanes form and we have a predicative capability using high resolution global and regional weather forecast models. We don’t understand rapid intensification. Like hurricane Harvey this year – it spun up very quickly, rapidly intensified, in less than 24 hours. We don’t know how to predict that much in advance. But in terms of track and overall intensity, rainfall impacts, we’re getting pretty good at being able to predict that. My company Climate Forecast Applications Network (CFAN) — hurricane forecasting is a big part of what we do, and we’ve have a really good year for our predictions.

The core observatory satellite scans Hurricane Irma on 5 & 7 September 2017.

DW:  What do we know about, looking backward, in the past, what do we know about the rate of change of the intensity of hurricanes, or the frequency of occurrence.

JC:  We only have good satellite data back to maybe 1980. We have some satellite date going back to 1970. But it is of lesser quality. We don’t have long global records. But in the Atlantic, we have pretty good historical records, at least for the landfalling hurricanes. But not necessarily for the total number in the ocean basins. For the satellite record globally, there’s no trend in the numbers or overall accumulated cyclone energy. We have teased out a signal, of increasing percentage of category four and five hurricanes in two of the basins in the Atlantic and the North Indian Ocean. But trying to determine whether this is natural variability or human-caused — we just don’t have a long enough record to tease that out. There are hints of an increasing percentage of category four and five hurricanes, but we don’t have the knowledge or enough data to attribute that to humans versus natural variability.

DW:  But some people have said that as a result of hurricane Harvey and Irma, that we live in a warmer world, the oceans are warmer, the sea level is higher, and this is going to make hurricanes more destructive. What do you think of that?

JC:  Can they then tell me why we’ve had no major hurricanes strikes in the US for the twelve years preceding Hurricane Harvey? Sea surface temperature is only one ingredient for hurricane development and intensification, and it doesn’t seem to be absolute sea surface temperature, either. You can go back and there were really strong hurricanes in the nineteenth century for example, where surface temperatures were significantly cooler. And there were some horrendous hurricanes in the Atlantic in the early part of the twentieth century, when sea surface temperatures were noticeably cooler. It’s more relative sea surface temperatures and the overall dynamics of the atmosphere that are arguably the key ingredients – not just absolute sea surface temperature itself.

We have a pretty good predictive capability of hurricanes right now. Our understanding of the climate dynamics of hurricanes is a different story. This is something that’s still a work in progress. There is a lot of debate in the scientific community about this, and we’re only now starting to see some high resolution global climate model simulations trying to sort out what we might see in the future.

There was a paper just published by a Japanese group: “Response of Tropical Cyclone Activity and Structure to Global Warming in a High-Resolution Global Nonhydrostatic Model” by Yohei Yamada et al. in the Journal of Climate. They ran the very high resolution Japanese climate model for the current conditions of perturbed warmer conditions, and they found a significant decrease in the number of hurricanes, but they found an increase in intensity, an increase in the horizontal size, which relates to storm surge among other things, and an increase in precipitation. I just glanced at it literally yesterday – I flagged it to read more carefully. That may be the best study that I’ve seen of that kind.

For the sake of argument, assume that is correct. What is the trade-off for 20% fewer hurricanes for a slight increase in overall intensity. In terms of overall damage. I don’t know what the trade-off is, so it might not be a net increase in actual damage if there’s fewer hurricanes. That’s the state of our understanding right now.

The first wave of the revolution in weather forecasting.

Photo of Jason-2. NASA/JPL photo on 30 June 2017.
Photo of Jason-2.  NASA/JPL photo on 30 June 2017.

DW:  So, given the models — what the models say — What people might say will happen in the future, how long will it be before we are observationally able to compare what’s happening with the models?

JC:  Kerry Emanuel has said that it will be mid-twenty-first century before we’d expect to see any climatological signal in the observations, because natural variability is so large. And weather roulette — sometimes crazy things happen, and then they don’t have anything to do with climate. By the time you have a long enough time — and this is assuming that we have some substantial warming over the next thirty years — if we do have substantial warming over the next thirty years, probably by 2050 we would start to be able to tease out a signal.

But looking at that period, the next 30 years, we’re probably looking at a shift in the Atlantic to the cool phase of the Atlantic multidecadal oscillation. In 1995, after a relatively quiet period in the Atlantic, we flipped to the warm phase of the Atlantic multidecadal oscillation, and that like really juiced-up the hurricanes. And so, at some time, probably in the order of ten years, we’ll see a flip to the cool phase again, and presumably much quieter situation in the Atlantic for hurricanes.

DW:  So are those who point to Harvey and Irma as being climate change in action, are they mistaking weather for climate?

JC:  Oh yes, they’re mistaking weather for climate. Harvey and Irma were big storms, but they’re don’t really rank up there with the worst that we’ve seen in the last decade or the last century. There were some horrendous ones earlier in the twentieth century. Including really bad ones that hit Houston and Florida. These aren’t particularly unusual as far as hurricanes go. They’re top-20 kind of storms, but they’re not record-breaking in any way, apart from the overall rainfall from Harvey, which was really more of a fluke from the weather situation that allowed the storm to sit in one place for a very long time. There’s nothing unusual about this hurricane season or about Harvey and Irma. The US had incredibly lucky run of 12 years without a major landfall during this active phase of the hurricane cycle. We were incredibly lucky. Our luck is now broken. But it’s totally expected.

Extreme lightning over the city.
Extreme lightning over the city. Vasin Lee/Shutterstock.

DW:  Can I ask you finally about event attribution? Because there are people saying that hurricane Harvey wouldn’t have happened without climate change., there are people say that the heatwave in Russia was made ten times more likely because of climate change, or the drought in America was made X-times more likely. Can I ask you what you think about scientists who try and attribute individual events to climate change in a direct way?

JC:  The group that I like is really the NOAA group in Boulder, who looks at the historical record and tries to see is there anything unusual. Looking back a hundred years, is this exceptional in any way? If it is not particularly exceptional, given the record we have for the last hundred years, then it’s hard to argue that climate changed. Occasionally we do get genuinely record-breaking events. Then we need to trace back to what was the atmospheric dynamics, and whatever that contributed to that event and you need to tease it out. It needs a lot of detective work.

There is this new movement to use climate models with natural variability, and then human-caused global warming, but these same climate models they’re using can’t resolve these extreme events. They can’t produce hurricanes, they don’t have the right event-weather distribution to provide heatwaves. It is just Voodoo statistics that they’re playing with these models — which do not have the capability to predict these extreme events in the current climate or an unperturbed climate anyways. I’m not very impressed with the model-based attribution arguments. Carefully-constructed diagnostic analysis and comparisons with historical events — to me those are of much more value.

DW:  So we have to wait and see?

JC:  We just have to wait and see. The IPCC Fifth Assessment Report Working Group I introduced this concept of time of emergence – when you would expect to see the statistics of the future climate breakout from the variability statistics of current climate, then they come up with something like 2050. We are not able to see a signal where the statistics would be genuinely different from what we have now. We’re not able to see that.

I don’t quite understand why it is important to attribute these extreme events other than to hysterically advocate reducing fossil fuels. In terms of trying to figure out how to manage extreme events and reduce our vulnerability, what’s causing it is almost a secondary concern. We’re not preparing for the events we have now, or the events we’ve seen in the twentieth Century, let alone for the events that we might see in the latter part of the 21st century. If we have enough money for that extra resilience – wow, that would be great to prepare for even bigger events than we’ve seen. But adapting and preparing for the ones we’re seeing now would be a big step in the right direction to reducing our vulnerability to what we might be facing in the future.

Thinking that reducing fossil fuels is going to help with extreme events on the timescale of the 21st century is a pipe dream. Even if you believe the climate models, and we are able to drastically reduce fossil fuel emissions by 2050, we’re going to see miniscule impacts on the climate and the weather by the end of the 21st century. Any benefits would be realised in the 22nd and 23rd centuries. If we think we have enough wisdom and knowledge to what might happen in the 22nd and 23rd Century — personally I’d rather see us deal with here and now, and maybe focus on what we might be facing out to 2050. That seems a more practical and realistic goal, for what we should be trying to do. That’s my opinion.


Judith Curry

About Judith Curry

Judith Curry recently retired as a Professor of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. She is now President and co-owner of Climate Forecast Applications Network (CFAN). Prior to joining the faculty at Georgia Tech, she served on the faculty of the University of Colorado, Penn State University and Purdue University.

She serves on the NASA Advisory Council Earth Science Subcommittee and the DOE Biological and Environmental Science Advisory Committee. She recently served on the National Academies Climate Research Committee and the Space Studies Board, and the NOAA Climate Working Group.

She is a Fellow of the American Meteorological Society, the American Association for the Advancement of Science, and the American Geophysical Union. Her views on climate change are best summarized by her Congressional testimony: Policy Relevant Climate Issues in Context, April 2013.

Follow Dr. Curry on Twitter at @curryja. Learn about her firm, CFAN, at their website.

The bottom line

“We don’t even plan for the past.”
— Steven Mosher (of Berkeley Earth), a comment posted at Climate Etc.

The public policy gridlock about climate change has left us unprepared for the inevitable repeat of past weather. This year the people of Puerto Rico paid for that. Next time the cost in blood and money might be even larger.

For More Information

To learn more about Hurricanes Harvey and Irma.

If you liked this post, like us on Facebook and follow us on Twitter. For more information about this vital issue see the keys to understanding climate change. Also, see all posts about hurricanes, about extreme weather, and especially these …

For a better understanding of climate change…

 The Rightful Place of Science: Disasters and Climate Change
Available at Amazon.

To learn more about the state of climate change see The Rightful Place of Science: Disasters and Climate Change by Roger Pielke Jr. (Prof of Environmental Studies at U of CO-Boulder, and Director of their Center for Science and Technology Policy Research). From the publisher…

“In recent years the media, politicians, and activists have popularized the notion that climate change has made disasters worse. But what does the science actually say? Roger Pielke, Jr. takes a close look at the work of the Intergovernmental Panel on Climate Change, the underlying scientific research, and the data to give you the latest science on disasters and climate change. What he finds may surprise you and raise questions about the role of science in political debates.”



11 thoughts on “Cut thru the myths about Irma, Harvey, and climate change

    1. SF,

      Pretty close to verbatim. I edited out the verbal ticks we all use. “So”, “and”, “you know”, and such — and the usual repetitions of phrases we use when circling to form coherent thoughts.

      Additions are in brackets {}. Such as spelling out acronyms and giving full citations.


  1. No landfall in 12 years? This is picking nits.. Hurricane Sandy made landfall as a ‘tropical storm’ only because it traveled so unusually far north. Hurricane force winds were experienced in both NJ and New York at landfall. Surely she must know this.

    In any case, why must a hurricane make landfall in the U.S.? It’s a phantom goalpost, and a common talking point of deniers. A scientist should know better than to propagate such nonsense.

    Next, she says, “They’re (Harvey and Irma) top-20 kind of storms, but they’re not record-breaking in any way… ” Absolutely false. Irma set a record for the strongest Atlantic hurricane ever measured so far east, which is significant– a fact she should know.

    Not to mention, the Atlantic isn’t the only ocean, or even the biggest one. The Indian and Pacific Oceans have seen massive “superstorms” the last several years, such as Haiyan, the warmest eye ever (2015-Patricia), and the strongest ever recorded in the Indian Ocean (2016- Fantala). Either Dr. Curry isn’t paying attention or she is cherrypicking. So let’s see if she has a history of cherrypicking.


    Of course, it’s possible she’s been misrepresented. After all, there’s the matter of very oddball, strawman questions, such as “Can I ask you finally about event attribution? Because there are people saying that hurricane Harvey wouldn’t have happened without climate change”

    Really? Harvey “would not have happened without climate change”? Who said that? Oh, “people” do. This is Fox News type tactics. So who is the “Global Warming Policy Foundation” doing the interview? Let’s see.

    “Its director is Benny Peiser,[7][8] an expert on the social and economic aspects of physical exercise, and it is chaired by former Chancellor of the Exchequer Nigel Lawson”

    So social scientist, not a physical scientist, and Thatcher lackey-cum-Neoliberal. In other words, Global Warming denialists who’ve set up a front organization to give the appearance of credibility and provide cover for their lobbying efforts.


    1. Oji,

      I see you are quite the science denier. I suggest you rely on the IPCC and the major climate agencies for information, instead of activists. Read this to see what they — and a wide range of climate scientists — say about hurricanes (quotes and links).

      (1) “In any case, why must a hurricane make landfall in the U.S.?”

      Because it is a statistically significant record of hurricane activity, going back to the late 19thC. Reliable records of hurricane activity over large ocean basins begin only in the mid-1970s with the satellite data.

      (2) “This is picking nits. …It’s a phantom goalpost, and a common talking point of deniers.”

      No, it’s data — which is why it is carefully studied by climate scientists. It’s weather, showing the high degree of variability in hurricane activity even over decadal time periods.

      (3) “Irma set a record for the strongest Atlantic hurricane ever measured so far east, which is significant.”

      The NYT article does not say that is “significant”. Are you making that up, or can you provide a supporting citation?

      (4) “The Indian and Pacific Oceans have seen massive “superstorms” the last several years”

      Global Accumulated Cyclone Energy has not increased — its trend is flat. That, and other data, are why NOAA and many climate scientists say that there is no visible trend in both Atlantic and global hurricane activity. See quite a few quotes and citations here.

      (5) You cite Skeptical of Science as an authority. No wonder you are so misinformed. Here is a comparison of a SkS biography with reality. Spoiler: its fiction. Read Curry’s bio (in the post) to see her professional accomplishments.

      (6) About GWPF.

      They just asked the questions and made the video. Let’s put your superstitious fears to rest: neither the transcript nor video are cursed.


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