August 31, 2017

Global Warming and Hurricane Harvey

It is more than a little disturbing.

Before the rains had ended, dozens of media outlets had published stories suggesting that global warming forced by humans (mainly by emissions of CO2 into the atmosphere) played a significant role in producing the heavy rainfall and resulting flooding associated with Hurricane Harvey.

Most of the stories were not based on data or any kind of quantitative analysis, but a hand-waving argument that a warming earth will put more water vapor into the atmosphere and thus precipitation will increase.  A few suggesting that a warming atmosphere will cause hurricanes to move more slowly.

This blog will provide a careful analysis of the possible impacts of global warming on Hurricane Harvey.  And the results are clear:  human-induced global warming played an inconsequential role in this disaster.  

Why did Houston Get So Much Rain?

The proximate cause of the disaster is clear: the extreme rainfall was the result of a hurricane/tropical storm that pulled in huge amounts of water vapor off the Gulf of Mexico (and beyond), and which came into the Texas coast and then stalled for days.   All tropical storms/hurricanes bring large amounts of rain during landfall.  What was different here was the stalling and sitting over the same region for days. 

So if you want to explain why this event was so unusual, you must shed light on the lack of motion after landfall of this strong hurricane/tropical storm.

And how much rain?  Here are the 7-day totals around Houston and the general area.   Over 20 inches in the region surrounding Houston (gray color), with the central areas getting 30-50 inches.  An amazing event.

The Global Warming Analysis

Let's analyze the two key questions:
  • Did global warming juice up Hurricane Harvey, producing unusually heavy precipitation?
  • Did global warming cause the storm to stagnate for days?
First, let us examine what we call the thermodynamic effects:  increasing temperatures and moisture.

 As air warms it can "hold" more water vapor, which can lead to heavier precipitation as the air enters a storm and rises.  In fact, more water vapor can also help rev up a storm as well, since when it condense it releases "latent" heat.  

There is a well known relationship between temperature and the maximum amount of moisture air can hold, the Clausius Clapeyron (CC) relationship, which says that air can hold about 7% more water vapor for every 1°C increase in temperature.

It turns out that there is a lot of theoretical and modeling work that suggests that extreme precipitation in storms might increase at roughly the same rate.  So increase the temperature of the air 1C and extreme precipitation might increase as much as 7%.  Keep this number in your will be important.

For the Texas coast, the temperature of the Gulf of Mexico will be critical, because the air that reaches the Texas coast will have passed over the water.

So how much has surface water or air temperature warmed up during the past decades?  One can go to the NASA GISS website and get the surface temperature change over the past 50 years during August.  The Gulf warmed by .5-1 °C between 1967 and 2016.  Pretty modest. Some of this was natural and some of it was forced by mankind.

But what was the SST anomaly (difference from normal) during the period that really counted here: the week before the hurricane. The NOAA sea surface temperature anomaly for August 20 to 26th showed .5 to 1 C warming above normal in the sea surface temperature for the northern Gulf of Mexico.  Less for the southern coast and right off Texas.

What about the air temperatures over the region in the previous days?  Were temperatures warmer than normal?  No...close to normal (white color)

So Hurricane Harvey developed in an environment in which temperatures were near normal in the atmosphere and slightly above normal in the Gulf.    The clear implication: global warming could not have contributed very much to the storm.

OK, let me go out on a limb. Let us assume that all of the .5C warming of the Gulf was due to human-caused global warming.  That NONE of it was natural.  And that the air was warmed by the same amount. Using the scaling described above implies an increase of 3.5% in the extreme precipitation of this storm.  So for places that received 30 inches, perhaps 1 inch resulted from global warming. Not much.  Immaterial regarding impacts or anything else.

Well, some of you might ask.  Is there any evidence of global warming producing heavier precipitation along the Texas coast?   Surely, if warming was evident and it was significant, precipitation would be increasing over time!

Well, here is the July to October (hurricane season) precipitation for the coast around Houston for the past 50 years.    Lots of ups and down but no trend.  In fact, if there is any trend it might be down.

I could show you a lot more, but bottom line in all this is:

There is no evidence that global warming is influencing Texas coastal precipitation in the long term and little evidence that warmer than normal temperatures had any real impact on the precipitation intensity from this storm.

Now, lets examine the second question.   Is there any evidence that global warming caused the storm to slow down?   Some of the media stories had all kinds of hand-waving speculations.  Such as the jet stream would be weakened and become "lazy" due to global warming.

Quite honestly, none of this is supported by observations or models.

The wind pattern that produced the stagnation is shown in the figure below, which shows the zonal (east-west) wind anomaly (difference from normal) at mid-levels in the troposphere (500 hPa) for August 18-25th.  A reasonable level to evaluate the steering flow for the storm.  Note that the zonal winds are more negative than normal (blue colors) over the Gulf, which implies stronger flow from the east (the convention is that winds going west to east are positive).   In contrast, there are greens and yellows over central Texas and to the west, implying more westerly (from the west winds), which would tend to slow the storm down.  So the large scale flow might accelerate the storm towards the coast and then slow it down.
But do we expect global warming to produce such a pattern of anomalous winds wind over the Gulf?  Are some of the media and "activist" scientists correct in saying that winds over the Gulf will slow down under global warming?   Let's find out.

First, let me show you the change in zonal winds over the Gulf of Mexico for the past 50 years at 500 hPa.  No real trend.   Other levels showed the same thing.

Tom Hamill, a scientist at NOAA ESRL, plotted the average hurricane speed in the region (20-30N, 50-100W), which I show below.  He also shows  (wisely) the number of samples (hurricanes) each year, since the reliability of the average declines when there are few samples.  It is clear that there is little trend, particularly when one only considers the years with decent samples.

Let me stress that it is the trend over the entire period that would suggest an impact of global warming, NOT some transient change over a few years.

What about the future?   Atmospheric scientists run global climate models driven by increasing CO2, with a large collection of runs being available (the CMIP5 effort with around two dozen models).   I did a paper with Matt Brewer analyzing these models (published in the peer-reviewed Journal of Climate) and below is figure from it, which shows the difference in the zonal (east-west) wind  at 500 hPa between the late 20th and 21st centuries for July and August.   Little change over the Gulf and that is AT THE END of the 21st century.  Little would change now.

 The bottom line in this analysis is that both observations of the past decades and models looking forward to the future do not suggest that one can explain the heavy rains of Harvey by global warming, and folks that are suggesting it are poorly informing the public and decision makers.

They are using hand-waving arguments to push an agenda, which observations, theory, and modeling show to be incorrect.  Global warming is a serious issue and mankind must deal with it, but hype and exaggeration of the current effects is counterproductive in the long term.

By the end of the century, increasing atmospheric moisture will increase the intensity of heavy rain in many locations, including the Northwest.   Although there is no evidence of increased hurricane frequency during the past several decades, some studies suggest enhancement of the number of the strongest hurricanes by the end of the century.

One does not need global warming to explain extreme weather--sometimes the factors come together to produce an unusual event... think of it as a meteorological royal flush.

What the media SHOULD be discussing is the lack of resilience of our infrastructure to CURRENT extreme weather.   Houston has had multiple floods the past few years and poor planning is a major issue.  When you put massive amounts of concrete and buildings over an historical swamp, water problems will occur if drainage and water storage is not engineered from the start.

China may be ahead of us in such planning, with a huge investment in their sponge cities program in which they are investing hundreds of billions of dollars.  Blaming global warming makes it easier to neglect the infrastructure investments that are required to protect our cites.

Can you imagine if President Trump announced an infrastructure program to make our nation more resilient to CURRENT extreme weather?   A bipartisan effort to deal with extreme winds, flooding, rain, drought, and other severe weather?


  1. Some media have been talking about infrastructure in relation to Harvey:

  2. "What the media SHOULD be discussing is the lack of resilience of our infrastructure to CURRENT extreme weather."

    I completely agree. Regardless of global warming, we need to move infrastructure ( other buildings) uphill about 10 ft nationwide. Away from the coast and river bottoms.

    All money spent on these low areas is really the equivalent of a financial and environmental crime or fools errand. Much of the worlds food transport infrastructure has chokepoints near sea level. This is very dangerous.-

  3. Great post. I immediately thought of your blog when I saw all the "this is what climate change looks like" stories in response to Harvey.

    Human-caused warming will be a big problem in the future, but alarmist language linking the latest drought, forest fire or flood to human-forced warming only gives air cover to denialists who will flip the narrative and cite anomalous cold-weather events as evidence that climate change is a myth.

  4. As usual great detailed comprehensive analysis!!

  5. Crickets from AGW crowd. Thanks for the science, Cliff!

  6. Thanks for your article. Someone like me who is aware of global warming can look around at all the extreme weather going on and feel as if we're in some sort of global warming end of days: Hurricane Harvey, huge wildfires in the west, our 110 degree weather in Sacramento (where I live). But it's really hard to pin climate change as the main driver of any of those particular events. Especially with forest fires, since forest mismanagement is such a huge cause.

    The point is that, how do we make progress? How do we work for policy that builds resilience in our communities? Is pointing at global warming as the culprit always the best approach? Thanks for being a reasonable voice and getting us to think rather than just react emotionally and instead consider what will actually accomplish something.

  7. From a layman, thanks for your calm and educated approach to explaining these things.

  8. For a *very* different take on Harvey and climate change, citing multiple studies by climate scientists, read:

    1. Thanks, useful to see that point of view. I noted that article considered more potential effects of global warming (such as arctic ice melt) that could be influencing storms like Harvey that don't always occur to some people.

  9. "There is no evidence that global warming is influencing Texas coastal precipitation in the long term and little evidence that warmer than normal temperatures had any real impact on the precipitation intensity from this storm."

    To this lawyer (and non-scientist) the global warming issues, along with this article, appear to be as much a word game as anything else. Is global warming "influencing Texas coastal precipitation in the long term?" Is there "any real impact?"

    For starters, some of the scientific community seem to think that global warming, or more accurately, this modern, man made version, is a much faster and much more unique and complex version of global warming. In fact, it's a version that has never been produced before on this planet. That alone makes it a special challenge for the scientists for they must analyze the data and look at weather and climate behavior, or the combination of behaviors beyond weather in ways they have never had to before. Both the data and interpretations and changing and challenging.

    Other scientists also would argue that one of the the first questions to ask is just what is the appropriate data to analyze for the cause and effect on the "Texas coastal precipitation?" Just Texas?

    And how do we prove "cause and effect?" Just the rain measurement?, wind speeds?, hurricane behavior? ocean heat?, atmospheric moisture? or a thousand other factors? What combinations? What weight to give each?

    Of course, most of the scientific community believes the "jury is still out" on the exact dynamics and relationships because, once again, we are in "uncharted waters." Climate science like its title is a very large, very new and very complex science. It's also, arguably now, one of the most important.

    To draw what appears to be "conclusions" in one direction or another, or to say "there is no evidence" this early in the game is a little ironic.

  10. Cliff, I think you focus too much on the weather in the Gulf while the weather in the Eastern Atlantic is where these storms originate.

    If you look at temperature anomalies at for the Eastern Pacific then you can clearly see that there's a >1.0℃ temperature anomaly off the coast of Africa and across the Atlantic.

    Then there's Irene where the temperature anomalies are >2℃ today at

    Kevin Trenberth points that out in "A look at that history indicated that the
    number of named storms and hurricanes in the
    North Atlantic had risen since 1994 and that,
    notably, the rise coincided with an increase in
    SSTs in a latitudinal region from about 10 to 20
    degrees north. This band of tropical water just
    north of the equator, stretching from Africa to
    Central America, is the critical zone of hurricane formation."

    Lots of NOAA articles conclude this as well. You can find them easily enough.

    I think you're looking for reason to not include more causes of the rise in stronger hurricanes for your blog (maybe it's because that's what you're reader want?). I'm going to place my bets on these analysis so I see no point in coming back here for weather since I can get that from NOAA already anyway. So long.

    1. Rise in number of named storms is irrelevant when they change the rules for which storms get names.

  11. Thanks for bring some rationality and solid data to the drama swirling around on this hurricane.
    I do have one question about your climate prediction paper (this is with all due respect and not trying to be argumentative because 1) I'm not qualified and 2) I am curious about the modeling).
    The ONE article on Harvey that did cite a scientific study that I saw quoted a paper by Michael Mann et al (Scientific Reports March 27, 2017) that used the same model (CMIP5) to predict jet stream behavior and came to a different conclusion (it is possible that I am misreading the correlation).
    How is it that the same model can produce different conclusions by different teams? Is it highly dependent on assumptions like a lot of fluid flow models (something I have experienced)? Like I said before just curious about the models not looking for a debate.

    1. Mann used a new and novel metric called Quasi-Resonant Amplification (QRA). Google Scholar only shows a few papers employing this in a climate context. It looks like Stephan Rhamstorf pioneered its use in climate studies.
      My analysis shows that high level, mid-latitude, summertime wind headings are just as zonal as ever, maybe trending a touch towards increasing zonality.
      My guess is that QRA Analysis gave Mann and Rhamstorf the result they needed to generate the headlines they were seeking. Confirmation bias at its finest.

  12. Climate change deniers will certainly grasp at objective posts that support their confirmation bias, just as others will prematurely accept media headlines that fortify their anxiety and concerns of the real issues associate with climate change. This is an opportunity to exercise our critical reading and thinking skills: comparing Cliff's post with Dr. Michael Mann's for example. C'mon people. Minimize the adjectives and let's post thoughtful analysis instead.

  13. Your negation is contradicted by the climate scientist Michael Mann:

    "... while we cannot say climate change 'caused' Hurricane Harvey (that is an ill-posed question), we can say is that it exacerbated several characteristics of the storm in a way that greatly increased the risk of damage and loss of life. Climate change worsened the impact of Hurricane Harvey."

  14. This is for C M but since you're not coming back here, you probably won't see this. Sad!

    The higher temperature anomaly in the Eastern Atlantic that you cite really only plays into the genesis of a storm like Harvey. Harvey formed in the Central Atlantic, fell apart in the Caribbean, and reformed in the southern Gulf of Mexico from the remnants of the trough that opened up in the Caribbean. The water temperatures off Western Africa had -ZERO- to do with how powerful Harvey became, or its cycloregeneration.

  15. Doc Wellness,
    Michael Mann is wrong for a number of reasons, but in his direct statements and his implications. Facts are facts....cliff mass

  16. Michael Mann, a noted activist AGW proponent made the mistake of blatantly ignoring science re: Harvey here:

    And he's not even qualified to discuss meteorology like Cliff Mass.

    Thanks for the science Cliff. The AGW camp and their media click-bait sycophants just don't seem to be able to hold back from seeing AGW in everything weather. And it is clear that this has completely disengaged the public and as you note, shifted discussion away from reasonable mitigation and prevention efforts.

    My guess is that people like Mann will continue to exploit tragedies like Harvey for their narrative even as the science clearly shows otherwise. They seem to be in to deep to give up now.

  17. I agree that the link between global warming and Harvey is being overstated, and that global warming did not caused Harvey to slow down. However, the SSTs in the western gulf have warmed due to climate change and the interaction between warmer SSTs and extreme rainfall is more complicated that just the Clausius-Claperyon relationship. There are other very important feedbacks on storm dynamics. You are also misleading readers with that SST anomaly plot. That plot uses a 1981-2010 baseline (not 20th century), includes the period when Harvey began to cause upwelling, and is coarse resolution missing a very warm narrow eddy that extended over the western Gulf. SST anomalies were closer to 1-1.5C. Its therefore possible that the additional boost in energy caused Harvey's explosive intensification and subsequent intense rainfall. We do not know the impact yet so you stating that the impact is likely 3.5% is as silly as Dr. Mann's assertions about the storm slowing down. I would be very interested in seeing a modeling study with varying SSTs to determine the impact of the Gulf's SSTs on Harvey. I imagine the differences are more complicated than we think.

    1. I calculated SST trend for northern gulf. Per HADISST trend there has been no warming since 1950. Per ERSSTv5, the warming has been 0.2C. Pretty small potatoes.

  18. Cliff - given the reality of AGW, when for you, does climate become weather? What would AGW caused or enhanced weather events look like?

  19. "Although there is no evidence of increased hurricane frequency during the past several decades, some studies suggest enhancement of the number of the strongest hurricanes by the end of the century."

    Another good example of the word game. Consistent this unprecedented man made version of a warming planet, some scientists believe many aspects of hurricane behavior are changing as well, not just frequency. Some scientists think the hurricane frequency could indeed drop but would also increase in their severity, strength, length, and many other and probably still to be discovered, UNIQUE characteristics. No scientist, including the one on this page can tell us conclusively whether this "unprecedented" water was or was not due to global warming

  20. Cliff,

    I remember some papers comparing Greenland ice cores to Santa Barbara basin cores from the late 90s, which indicated that past Holocene climate changes occurred much more rapidly than previously thought; increases up to 5 C in a few decades.

    Is this something that's been disproven since then, or is it something the current models can't account for?

    Thanks for your wonderful blog.

  21. Many of the Media put as much thought into this issue as Inhofe and his Senatorial snow ball. The same media predicts the "Storm of the Century" whenever Seattle is about to get a little blow. They did many a disservice recently predicting "Trafficmageddon" and several in the region stayed home during the eclipse - even in Portland - missing perhaps what could have been one of the most rare and beautiful moments in their lives. The two minutes of Totality that I witnessed doubled what I have seen in my 62 years. The media took a minor toll on me as I was responsible for some Japanese scientists visiting and wanted to give them a memorable experience and this hype caused all sorts of undue worry. We had a fantastic time!

    Our society needs a better understanding of Science and its Dynamics. Instead, both sides on an issue such as Global Warming passionately elevate their meager understanding into belief systems and the one side that badly needs to be convinced about this rightly accuses Science of being another Religion, in terms of most peoples' understanding of it. They just incorrectly assume that the Scientists working on these issues also are believers.

    But a scientist such as Cliff Mass doesn't believe in Global Warming. Instead, he observes and measures it and its effects - and understands what types of things are caused by it and what types of things aren't. In this case, Harvey, not to mention the dry winter we had last year and this summer's exceptionally dry weather. The understanding of Global Warming is dynamic and changing - it sometimes takes years for the science and knowledge and techniques to catch up before we have a grasp of what is really going on.

    For instance, soot and its effect on ice in Greenland is just being studied. This rather than warming might play a bigger role in the melting of the ice cap. It could be argued that increased fires are contributing to the increased soot. But so could China's rapid industrialization which is most definitely not caused by Global Warming - although it is a major contributor to it. The increase in the number of cargo ships crossing the oceans could be creating this increased soot load.

    We need more scientists running our government than buffoons who only wish to enrich themselves and inflate their own egos!

  22. How much did sea-level rise over the last 100 years decrease Houston's ability to shed Harvey's water?

  23. "By the end of the century, increasing atmospheric moisture will increase the intensity of heavy rain in many locations, including the Northwest. Although there is no evidence of increased hurricane frequency during the past several decades, some studies suggest enhancement of the number of the strongest hurricanes by the end of the century."

    Which makes it fair to say that Harvey is in some sense a preview of what global warming will bring. It's easy to slip from that into claiming that Harvey was caused by global warming, which I agree is an unsupportable claim.

  24. "4. Conclusions

    [13] Heavy precipitation events associated with TCs represent about 6% of the coterminous U.S. total. There has been a recent dramatic increase in this number. During 1994–2008, this number was more than double the long-term average. The total annual national number of events was about 25% above the long-term (1895–2008) average during this same time period. Despite the limited spatial area and portion of the annual cycle affected by TCs, the anomalous number of events associated with TCs accounted for over one-third of the overall national annual anomaly. While there has been a recent increase in the number of landfalling U.S. hurricanes, the increase in TC-associated heavy events is much higher than would be expected from the pre-1994 association between the two. Much of the Gulf and Atlantic coastal areas have experienced an increase in the frequency of such events associated with TCs."

    "As Harvey approached the Texas coast last week, the Gulf ocean temperature rose 2.7 to 7.2 degrees Fahrenheit above average. “That provided a deep, warm pool of water used as fuel,” says Dalia Kirschbaum, a research scientist at NASA’s Goddard Space Flight Center who studies hurricane hydrology. Harvey used this hot spot to shift from a tropical depression to a category 4 hurricane in roughly 48 hours."

    Reiterates connection but how difficult it is to be definitive(one way or another) - because of the complexity:

  25. Mmm, Cliff, I've been following the press articles mentioning you this week and after reading this blog post I'm going to respectfully be a thorn-in-your-side ex-graduate student here and call you out on this article.

    I agree that the media is too quick to jump on the AGW bandwagon with any large weather disaster; saying Harvey was caused by AGW is unsupportable, and at this point even saying Harvey was worsened by climate change is largely conjecture. It will take months, if not years, to conduct the research to properly pull apart the drivers behind this storm and begin to determine the level to which climate change might have played a role. However, with all due respect, while you have called out hand-waving arguments on the part of those claiming that Harvey may be a sign of the type of storm we will see more of in the future, your arguments to the contrary are fairly hand-waving too. A cursory linkage of SST anomalies and the CC equation is enough to establish a hypothesis to later prove or disprove via the scientific method, but NOT enough to issue the definitive statements like “There is no evidence that global warming is influencing Texas coastal precipitation in the long term and little evidence that warmer than normal temperatures had any real impact on the precipitation intensity from this storm”, and “The clear implication: global warming could not have contributed very much to the storm.” I’d say that contrary statements made by folks like Kerry Emanuel and Kevin Trenberth are backed up by more research.

    I know that this is a mission against media hyperbole and shoot from the hip statements made by climate scientists who are so passionate about the risks of climate change that they sometimes are too quick with attribution. I get it, and I think you have a point. However, I also know that you believe that AGW is an existential threat. Which message is more important to you? Because of your amazing work educating the public you are now in a position of extraordinary influence, and thus responsibility. Looking through the comments to this blog article, I’d say it’s played a role in pushing back the day when the public stands up in large enough numbers to demand “ENOUGH - OUR KIDS MATTER AND WE MUST ACT AGGRESSIVELY TODAY TO STOP DESTROYING THEIR FUTURE STARTING TODAY”.

    You taught me how to communicate science to the public, and extended a long line of science communicators influenced by Carl Sagan, and you taught me well. We should always be honest with the public. But I wonder if your desire to call out climate change hyperbole has you not seeing the forest for the trees?

  26. I know that this is a mission against media hyperbole and shoot from the hip statements made by climate scientists who are so passionate about the risks of climate change that they sometimes are too quick with attribution. I get it, and I think you have a point. However, I also know that you believe that AGW is an existential threat. Which message is more important to you? Because of your amazing work educating the public you are now in a position of extraordinary influence, and thus responsibility. Looking through the comments to this blog article, I’d say it’s played a role in pushing back the day when the public stands up in large enough numbers to demand “ENOUGH - OUR KIDS MATTER AND WE MUST ACT AGGRESSIVELY TODAY TO STOP DESTROYING THEIR FUTURE STARTING TODAY”

    Wow! So you know he's telling the truth, but you want him to lie for the cause. You are in a cult, and badly need deprogramming.

  27. Cliff..

    I think you might choose to address Jeff's concern above that the SST anomaly map that you use references a baseline of 1980-2010. If the SSTs are compared to the 1960-1991 average the gulf was anywhere from 1.5-4 degrees Celsius warmer than normal. This seems significant. Even if increasing precipitation 20-30% above normal, these warmer waters could have made an already catastrophic storm that much worse.

    I think these dates are the fair ones to use in this instance as NASA/goddard uses these dates in setting the base "average" temperature on their graphs. Correct?

    (link to map of the SST anomaly for the gulf on August 23, 2017; 1960-1991 baseline)

  28. Sharply focused:

    The problem is not what Cliff says, because literally no one can find substantial fault in it, as you point out.

    Also as you point out, there is fault in what he doesn't say. There is an error of omission.

    Not directly relevant, but entirely analogous, is the "error of omission" in any insinuation, allusion, inference, heuristic short cut or Dog Whistle that is levered to such great effect by certain well known and extremely powerful politicians. Depending on which "team" you are on, we will react with either revulsion or smug satisfaction at the cleverness in communicating by what is not said but effectively messaged anyway. I repeat that I don't imply that this is Cliff Mass's intent or even effect so much as how we interpret what is not being stated - similar to choosing to see or not see an elephant in a room.

    I entirely agree with and often applaud his efforts to point out gross hyperbole that serves only to distort and deceive.
    But no one can ignore - and to his credit Cliff states unambiguously - that he choses to focus only on gross hyperbole in one political camp only. That honesty and transparency is rare and should be appreciated even if only for that reason. But no one can deny that many of us could give a rat ass for ethics of empiricism - we really only care about winning by any means necessary and all and any error of omission becomes ammunition for those who consider science a political team sport.

    That is just a grim reality best not naively ignored. We can assume that Cliff and his professional peers will continue to minimize this subversive politicking of science - after all, that is their historical record. We can also assume with great confidence that the rest of us won't. That also is well documented in the historical record.

  29. Sharply Focused,
    As always, I respect your opinions. But you this time I must push back. My arguments are not hand-waving. They are explicit and based on observations and science. You know about the Clausius Clapeyron relationship as well as I do. A small increase in temperature only produces a small increase in water vapor in the atmosphere. They is a large literature on increases of extreme precipitation as the earth warms. The small warming of the past decades could only have increased the precip by a few percent. Not handwaving. The lack of evidence for changes in winds over the Gulf or hurricane motion, is observed. Not handwaving.
    Your basic argument is that I should not talk about the truth because people have to do something about global warming.

    Here we disagree. I believe the ONLY was to get bipartisan support for taking on climate change is to carefully stick to the truth. Easily disproven hype and exaggeration undermines our ability to work towards real solutions. The leaders of Houston have been very irresponsible by promoting mindless development without considering flooding. Do you want to give them a pass, saying it was GW's fault? I hope not....cliff

  30. I wanted to say thank you for posting an open analysis here.

    There are far too many ridiculous claims floating around the internet that are preventing a proper focus on the lessons we can learn to protect the gulf coast in the future. A prime example is Michael Mann's implication that a 4 foot storm surge in Galveston Bay substantially worsened flooding in Houston because of rising ocean levels? Really?? With no data to back it up. I doubt the homes along Galveston Bay itself had any problem at all from the storm surge, much less Houston at 50 feet above sea level.

    As correctly stated, the focus now should be on remedying the infrastructure deficits that contributed to this disaster. I hope Houston realizes that this is not the 1940s anymore, and the previous plan designed to protect 1930s downtown is worthless.

    However, we always seem to prepare for the last disaster instead of anticipating the next. The New Orleans levees were built to handle Betsy. But we failed to pay attention to what would have happened if Camille took Betsy's path. So then Katrina came along, and even that could have been far worse.

    Could New Orleans handle the 60+ inches of rain that Wilma put down over Mexico in under 24 hours? I think not.

    With regard to climate change, how can we possibly expect the public to unify behind a policy of long term change for the planet when the voices in the media are so foolish? Any progress made is lost when attempts to instantly attribute every single hurricane, drought, fire, flood, etc to climate change without any thought or rationale are such clear nonsense. That is not science anyway, and it undermines the credibility of the scientific community as a whole.

  31. Bill Reiswig,
    The first surface temp/SST map has no is a trend. So there is no problem...similar SST change. Not sure where you got your number...too large...cliff

  32. Several commenters say that its all irrelevant because we "need to do something to prevent catastrophe." Well, there are an large number of potential catastrophes to deal with. We have only limited resources. I personally believe that in general there is a strong tendency for the media to exaggerate to get people to tune in. Scientists also can fall into this trap because if their problem is "huge" then huge funding should be allocated to it.

    Cliff's point about resilience is very important. We don't even plan for yesterday's weather. Infrastructure that is resistant to extreme events is a big win and everyone can agree on it. Let's get busy and pay for it. First thing is to cancel Federal flood insurance that subsidies people who build near the coast and low lying areas. subsidize people who move to higher ground.

  33. Dear Cliff, I read your words, as do many I know, and respect you. You write "Global warming is a serious issue and mankind must deal with it" YES! This is more important than all the rest of the effort you put into disproving that global warming did or didn't contribute to Hurricane Harvey. This is also more important than those who mistakenly point to global warming as the cause of every little thing. But, absence of evidence is not evidence of absence. The world is warming and it may be curtains for civilization as we know it. I do not care if it's God's will or the aliens fault or the cow's farts. What are we willing to do about it? You say they are pushing an agenda. Perhaps the agenda is, again, as you put it..." mankind must deal with it" And I do not see us as a nation dealing with it. Please help us. You have a well respected voice. Help affect the change needed. I am so worried I want to try all the changes put forth and if we can modify this trend, then we can select the most effective climate saving practices and discard the others. But until we actually do something, it's all just fiddling while Rome burns.

  34. Hi Cliff,
    One thing that you haven't addressed is the rapid intensification of recent hurricanes. We've seen in recent years several hurricanes jump from a TD to a major hurricane within a very short period of time. Is there a trend towards rapid intensification or just a lack of historical perspective on my part?

    Thanks, as always, for your insightful posts.

    Bill Clugston

  35. One thing that you haven't addressed is the rapid intensification of recent hurricanes. We've seen in recent years several hurricanes jump from a TD to a major hurricane within a very short period of time. Is there a trend towards rapid intensification or just a lack of historical perspective on my part?

    That would be a lack of historical perspective on your part. Harvey wasn't a particularly intense hurricane. It was an unusually stationary one.

    Contrary to the failed predictions of the Worldwide Cult of Global Warming, there have been fewer hurricanes than average for the past few decades. And there's been no change in their severity. You would never know this from listening to the True Believers who cling bitterly to their disasters and their religion.

  36. But I thought hurricanes are generated way out in the Atlantic Ocean and not just in the Gulf. Study doesn't seem complete.

  37. The difference between religion & science is that religion barrels on in its orthodoxy, hate on us atheists, inanity & insanity, despite evidence.
    Science can alter its position radically, if it remains science.
    Politicians are not invited.
    Alarmists & deniers continue their fear-mongering ...
    and continue to claim politicians can change anything & everything—including long range patterns in the weather, aka climate—thru taxes, bureaucrats, larceny, and war...

  38. I looked up this blog after hearing you state your opinion about Harvey and global warming on your “Weather With Cliff Mass” podcast. You sum up your argument there by saying you take issue with “some” of the media, who, you say, “have really hyped this up”.

    I went looking for the hype.

    I read the articles and editorial you specifically refer to in this blog post, i.e. those published by the Los Angeles Times, the BBC, and Politico. I looked at any article referenced by these as well.

    Since your podcast is posted for the members of the general public who are interested in a discussion of regional weather, anyone would assume that what you are saying is intended for the general public, and that what you are saying is that the media is hyping up a Harvey and climate story into something that most climate scientists would not support.

    You should make your argument with the climate scientists you disagree with instead of adding your voice to those who would attempt to discredit the most reputable media outlets that exist.

    For example, your blog post has a screenshot of a BBC article, as your second example of the “dozens” of media piling on the hype.

    Dr. Rahmstorf is quoted in this article saying: "This is a consequence of the disproportionally strong warming in the Arctic; it can make weather systems move less and stay longer in a given location - which can significantly enhance the impacts of rainfall extremes, just like we're sadly witnessing in Houston”. The next paragraph cites Dr Friederike Otto saying the opposite: “I don’t think we should speculate on these more difficult and complex links like melting in the Arctic, without looking into these effects in a dedicated study”

    It appears your problem is with Rahmstorf, not the BBC. Take him on directly.

    Although the LA Times editorial you feature a headline from at the top of your blog post does go too far, with its use of the word “certainly”, i.e. global warming “certainly makes such storms stronger, more unpredictable, and quicker to intensify”, the editorial points readers interested in further information to Chris Mooney’s Washington Post article “What you can and can’t say about climate change and Hurricane Harvey”.

    Mooney’s article has nothing to do with hype. Eg, Mooney writes: “Singling out Harvey as some kind of climate driven anomaly would be a big mistake”. He discusses the issue. He cites Dr. Emmanuel’s recent study which found “the incidence of storms that intensify rapidly just before landfall increases substantially as a result of global warming”. Argue with that. It isn’t the Washington Post’s fault that a prominent hurricane researcher like Kerry Emmanuel published a study that found that.

    When discussing Harvey’s slow movement over land, the LA editors point readers to a Dr. Mann Nature article.

    When did it become “hype” to cite the most reputable journals, or to quote the most respected scientists?

    Don’t pretend almost all climate scientists are on the same page with you as you assert that some of the media are hyping this up.

  39. David Lewis raises a good point. When you have conflicting opinion with your peers, a forum designed for the public is hardly the right place to do battle.

    Most of us are familiar with Cliff Mass as a personality but few of us are familiar to any competent degree with the actual science. This is a classic scenario where the logical fallacy "appeal to authority" has no merit. You can certainly tell us that there might be some controversy among you and your peers but you telling us who is right serves nothing, because we can't judge.

    Other than what we know, which is whatever appeal personality might have.

  40. Statistics is not "appeal to authority". Neither is the insignificance of the data vis-a-vis climate change as a phenomena that occurs over time periods of centuries/millennia. The ones who beg for a political, authoritarian reaction have a political agenda; their alleged science is but a screen.
    And fortunately politicians, taxes, bureaucrats, and hate remain curiously aloof from the Earth, its climate, and true science.

  41. Last weekend I came across this NASA site (Earth Observatory) which shows the SST in the vicinity of Southern Texas on August 23 and 30 as high as 1.5 to 4 degrees C above normal:

    This is significantly higher than the 0.5-1.0C used in Cliff's blog. Would that high level of temps be enough to counter his argument?

  42. japaero
    I checked again at the NOAA site and your numbers of not correct. Most of the Gulf had a .5 to 1 C anomaly. To confirm, please go to this NOAA website:

  43. Ask me in a 1000 years, when such trends have been continued and now they have statistical significance
    You all are like divining prophesy from fish entrails ...

  44. @placehold:
    "Wow! So you know he's telling the truth, but you want him to lie for the cause. You are in a cult, and badly need deprogramming."

    No, that is not what I'm saying at all. Cliff wrote this article because he's worried about hyperbole in the climate science world. That hyperbole DOES exist. See, I'm not asking him to lie - I'll happily say it myself. However, it is NOT the mode within the science community. It sure is within the "do nothing" camp though, with a double dose of flat out lies to boot. We are in dire trouble...that is not hyperbole. The quantity of heat being added to the earth system, especially the oceans is STAGGERING; I won’t go into the math but the rate of heat energy increase in the oceans (most of which is due to increasing GHG concentrations) is orders of magnitude higher than the rate of use of energy by burning fossil fuels. And its cumulative. Those GHG’s have a very long residence time; even if we stop today the warming will continue. The accompanying acidification of the oceans is equally disturbing and probably irreversible even through geo-engineering using as yet not invented technology. So sure, I could grouse about the minority in our community who feed the media what they want to hear, or I could criticize the rest of us for not jumping all over them. But I choose not to. Why? Pragmatism. Not because, I don’t want everyone to understand every nuance, but because I have limited resources for outreach and I'd rather be part of the solution than in inadvertent and well-meaning part of the problem. I've been at the point of pleading with Cliff to stop for some time now. I spent three hours last night trying to compose something to him that might allow him to see the bigger picture. Trust me, that's not because I need deprogramming. I don't know if this mission he's on is just mis-guided or if he relishes stirring the pot, and the attention it brings, but the responses it is bringing out, as evidenced here by your comments and those of others, make it abundantly clear to most of us in the community that he is doing terrible damage. I'm shocked that he cannot see that. Paraphrasing other commentators, "Please Cliff, use your influence to help us with what really matters."

  45. @SharplyFocused, you don't know what you are talking about. In itself, that's actually okay, because it's impossible for everyone to know what they ought to know about everything. But you pretend to know anything, and that is the problem.

    I call it the "progressive disease." Your crowd has utterly no appetite for facts, but you have an inexhaustible appetite for pretense. And you go so far as to attack anyone who tells the truth, including Cliff Mass, because he fails to run around with his hair on fire and tell lies like you clearly want him to do.

    Anthropogenic global warming is a hypothesis and one that has failed its own predictive tests. The statistical foundation is built on quicksand, and the method of inquiry was faulty from the start. Now we have an entire AGW establishment built on a failed hypothesis, to the degree that we have politicians masquerading as scientists who are actually falsifying the historical temperature records to "prove" a hypothesis that failed a long time ago.

    You bet we're in trouble, but not the kind you seem to think.

    1. Placeholder, There's a huge amount of don't know but one thing I do know is that Cliff and I agree that AGW is real, and agree that data and research indicate it's consequences will have a profound impact on humanity. We also agree that we should act now, and we both support a carbon tax. Sorry to burst your bubble.

  46. Bruce, I appreciate your well thought out commentary here. I'm torn myself. I get the tack he's taking and applaud him trying. Comments here suggest to me that it's backfiring but he's told me offline that he thinks he's gaining some influence with powerful deniers who think twice when he subsequently tells them that AGW is real and extremely serious. I sure hope that this precarious balancing act falls on the right side of history. Things look pretty bleak right now.

  47. As usual, humanity is blundering along, not knowing the consequences of our actions. Science is showing us in bits and pieces of how that is as true today as it ever was. We think we are so smart, but....
    If it's made by humans, it's not failsafe!

    •Nuclear power, not failsafe and nowhere to put the leftovers.
    •Building our homes and industries on the flood plains and being surprised at flooding.
    •Burning fossil fuels and finding scary results.
    •Fishing all the fish out of the seas, unsustainable farming, and cutting and burning forests all over the globe.
    •Sucking all the clean freshwater up and throwing it away polluted.
    •Inventing scary technology like GMOs.

    But most if all, breeding like flies in the garbage dump.


  48. Hi Cliff,

    In the SST anomaly data you used, the baseline is from temperature averages from 1981-2010, well after the effects of global warming have already been felt. If you shift those baseline to an earlier, and more appropriate, year range, the SST anomalies are much more skewed in the positive direction.

    Of course if you're using a baseline of recent years, the SST anomaly will appear "near normal." The baseline absorbed a huge chunk of the temperature anomaly.

  49. Tyler
    That is why I showed TWO SST figures, the first has no baselines and is the trend. It shows that the increase in SST has not been large...cliff

  50. Cliff,
    But what was the SST anomaly (difference from normal) during the period that really counted here: the week before the hurricane. The NOAA sea surface temperature anomaly for August 20 to 26th showed .5 to 1 C warming above normal in the sea surface temperature for the northern Gulf of Mexico. Less for the southern coast and right off Texas.

    Maybe someone else has already pointed this out, but according to the figure that I think you're referring to the baseline is 1981-2010. Therefore, you seem to have defined normal as the average of the last 30 years, rather than - for example - what would have been in pre-industrial times. Hence, it would seem that anthropogenically-driven warming could larger than you suggest.

  51. It was very disturbing to read this about climate change denial in this day in age and try to pass it off as "we can do resilience instead" and look away from actually fixing global warming. We have lots of equipment and data that shows lots of connections that this is human caused warming.

    First off from the EPA:(in regards to lots of rain and drainage problems caused by climate change sea level rise)
    "Sea level rise is already worsening water levels during high tide; posing challenges to near term management of water infrastructure. Higher water levels during tides can reverse or reduce efficiency of stormwater drainage and wastewater outfall operations. Some coastal communities are already investing in one way stormwater valves to address more frequent and intense flooding during high tides."

    Then go to to see sea level rise across the global continuing to increase and not go down, not leveling out.

    Then you can click on carbon dioxide levels due to human activities. Its showing only increasing.

    Then you can also watch NOAA weather school video and experiment that is easy to reproduce (I need to do a video on it also)

    With the above peer reviewed data from NASA and EPA I conclude that you completely missed out on human caused sea level rise in your data. Its not too soon, it may have been too soon 20 years ago, but I personally just hope its not too late.


    Numerous articles online talk about Houston not funding any infrastructure programs for flooding and sea level rise. Their infrastructure is so old as its taking on almost all of the sea level rise we have been measuring. Florida on the other hand has passed sea level rise programs. While we need infrastructure protection, we also need programs to stop making it happen ASAP.

  52. Here's a well written, generally level headed article that people should consider reading. It comes with references to research, and while it is clear that the author is concerned about the impacts of climate change, it articulates an appropriate level of uncertainty. It doesn't say anything like "Irma was made worse by climate change", or "There is no evidence that global warming is influencing Texas coastal precipitation in the long term..." but tries to decipher peer reviewed research, and where the author is being anecdotal, I think he's made an honest effort to indicate such:

  53. Surprised at Cliff’s focus at our synagogue

    Back in 2013, I was involved in formulating a Statement on Climate Change, as part of a larger Social/Environmental Statement, at my Jewish congregation in Seattle. We referenced extreme heat, wildfire, storm, events as stated by the IPCC to be become more and more likely with Climate Change.

    Cliff, you wrote a note to me, and cc’d the rabbis, that was a scathing rebuke of our references to any extreme events, saying:

    “I believe the work to help mankind find a sustainable way to live with our planet--work of great importance-- is greatly undermined by claims such as noted above, claims that are easy to disprove and which aid, rather than work again,  the "deniers, the fossil fuel industry, and others to maintain the status quo".

    It is not that I don’t respect your expertise, or the sincerity of your views on attributing extreme events to Climate Change. And I attended a thoughtful, informative presentation you once delivered on climate change to the congregation. But I found it deeply disturbing, that by the tone of your rebuke, however unintentional, you were “undermining” our fledgling effort at the synagogue. There was not one iota of support in your note for the overall effort in the congregation.

    I thought it very odd at the time, and now see it in perspective. I appreciate the thoughtful analysis and urging of Sharply Focused. Yes, mode of expression is of critical importance, and I fear your expertise, together with you crusade against supposed media hyperbole, will be sadly misused by climate deniers.

    Cliff, I hope you consider the tone of your admonishments, and consider coupling them with news on our appalling and perilous march towards doom. I urge you, as a public figure, to of course say what you believe to be true, and, to not make the needless and harmful error of omission. This, I believe, would be speaking the “greater” truth, and would be a real service to humanity.


    Barak Gale

  54. Barak.... it is critical that scientists provide the truth and not exaggerate the impacts of climate change. Should one not tell the truth about extreme events to somehow be motivated by the "greater truth." Very dangerous. Sharply Focused is one of my past students and we have debated this issue. And when someone starts focusing on the "deniers", I really start worrying....cliff


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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