Sorry, deniers & delayers, Part 1: Even U.S gov says human emissions are changing the climate

The U.S. Climate Change Science Program (aka the Bush Administration) has issued a must-read report, Weather and Climate Extremes in a Changing Climate. It wouldn’t be must read or even big news if it weren’t for the fact that

  • Many environmentalists stopped talking about the extreme weather/global warming link a decade ago.
  • The deniers, the delayers, and of course the Roger Pielkes of the world have pushed back against any claims that climate change is driving the extreme weather we see today [as Chico Marx (dressed as Groucho) said “Who you gonna believe, me or your own eyes?]
  • The media has been brow-beaten by the deniers into downplaying the connection. The journalist Ross Gelbspan has a long discussion of this in his great 2004 book, Boiling Point — I will blog on this later.
  • The Midwest is experiencing the second “500-year flood” in 13 years. [Don’t worry, big media, it’s all just a big coincidence like the deniers keep saying.]

This report is really an “I told you so” from NOAA’s National Climatic Data Center and Tom Karl in particular, who has been a real leader in this area, helping to create the still rarely-discussed Climate Extremes Index (see “Global warming causes deluges and flooding, just like the Midwest is seeing (again).”

If you don’t read the whole report, at least read the synopsis:

Changes in extreme weather and climate events have significant impacts and are among the most serious challenges to society in coping with a changing climate.

Many extremes and their associated impacts are now changing. For example, in recent decades most of North America has been experiencing more unusually hot days and nights, fewer unusually cold days and nights, and fewer frost days. Heavy downpours have become more frequent and intense. Droughts are becoming more severe in some regions, though there are no clear trends for North America as a whole. The power and frequency of Atlantic hurricanes have increased substantially in recent decades, though North American mainland land-falling hurricanes do not appear to have increased over the past century. Outside the tropics, storm tracks are shifting northward and the strongest storms are becoming even stronger.

It is well established through formal attribution studies that the global warming of the past 50 years is due primarily to human-induced increases in heat-trapping gases. Such studies have only recently been used to determine the causes of some changes in extremes at the scale of a continent. Certain aspects of observed increases in temperature extremes have been linked to human influences. The increase in heavy precipitation events is associated with an increase in water vapor, and the latter has been attributed to human-induced warming. No formal attribution studies for changes in drought severity in North America have been attempted. There is evidence suggesting a human contribution to recent changes in hurricane activity as well as in storms outside the tropics, though a confident assessment will require further study.

In the future, with continued global warming, heat waves and heavy downpours are very likely to further increase in frequency and intensity. Substantial areas of North America are likely to have more frequent droughts of greater severity. Hurricane wind speeds, rainfall intensity, and storm surge levels are likely to increase. The strongest cold season storms are likely to become more frequent, with stronger winds and more extreme wave heights.

Current and future impacts resulting from these changes depend not only on the changes in extremes, but also on responses by human and natural systems.

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17 Responses to Sorry, deniers & delayers, Part 1: Even U.S gov says human emissions are changing the climate

  1. David B. Benson says:

    And then there were, recently, a few hurricanes in the Mediterranean, so-called Medicanes.

  2. civil behavior says:

    Thank you Joe Romm for your consistent educational discourse on the most important issue facing this species.

    Thank you for this blog.

  3. Paul K says:

    There is not one shred of evidence that the less than 1C last century warming has any thing to do with midwest flooding. It is sophomoric to pretend there is a connection, especially when the floods are in an area that is measurably cooling.

  4. John Hollenberg says:


    I guess you didn’t read Joe’s post and the conclusions of the report of the U.S. Climate Change Science Program? Of course no one can ever say that a specific weather event is caused by global warming, only that an increased frequency of these types of events is predicted to occur (which is what the Climate Extremes Index is showing).

  5. Nylo says:

    Saying that the frecuency of weather extremes will increase is the same as saying that we are a bit guilty of each one of them.

    If U.S. gov says that human emissions are changing the climate, I have to agree with them.

  6. Abhijeet says:

    Forgive me if this is repeated information, but here’s a link to James Hansen’s paper 20 years after his historic testimony to Congress warning us.

    The arctic is visibly melting, but try telling that to the obnoxious, opinionated, narcissistic, loud-mouthed right wing talk show radio host and his/her largely ignorant audience.

    Keep up the good work, Joe. The world is indebted to you. The next Nobel Peace Prize should go to the collective body of media dedicated to raising awareness about GW (Global Warming; not the dim-witted 43rd president!, though another Peace Prize should go to all those who expose the terrible consequences of his two idiotic terms too).

  7. Paul K says:

    The arctic is visibly melting and top NASA scientists determined decadel ocean oscillation has greater impact than AGW. I looked at the 1998 testimony. There are three scenarios projected. You can go ahead and tell me that actual temps are not much lower than the two scenarios that are based on business as usual and longterm ppm growth trends. Actual temps are still a bit below but closest to the third scenario. The shocking thing is that in this scenario CO2 emissions were significantly reduced from 1990 to 2000.

  8. Gary Herstein says:

    Let me see if I’m clear on this:

    1. Warm air lofts more moisture.
    2. Warm moist air becomes precipitation when it encounters cooler (and hence, drier) air.
    3. Global warming predicts that there will be shifts in precipitation patterns, including the lofting of significant volumes of moisture.
    4. Nevertheless, “It is sophomoric to pretend there is a connection [between global warming and the midwest flooding], especially when the floods are in an area that is measurably cooling.”

    1 through 3 would seem to argue — almost demonstrate — that flooding is exactly what you would expect in an area that is measurably cooling, since that is one of the areas that will receive unprecedented precipitation from the excess moisture in the air.

  9. Paul K says:

    Gary Herstein,
    I get it now. Warming causes more flooding except when it is cooling. Then it’s the cooling that causes more flooding. Are you claiming there has been unprecedented precipitation this year?

  10. David B. Benson says:

    Gary Herstein — Warm moist air produces condensation, i.e., clouds, when it is lofted high enough to cool and so saturate. Clouds become precipitation when there are aerosols present to act as condensation nucleii.

    Which wasn’t quite what you wrote.

    Paul K — All other things being equal, warmer air holds more water vapor. Hence with global warming more extreme precipitation events are to be expected.

  11. Gary Herstein says:

    No Paul; the “500 year flooding” in the midwest has been caused by the extreme drought in all the feeder rivers and tributaries. Or maybe that water is actually coming from somewhere? Like, you know, from rain? And gosh, you don’t suppose that the “global” in the phrase “global warming” might have some operational relevance, maybe even more than just the midwest? I’m just asking …

    Thanks to David for the additional info about the aerosols. Please (seriously, as opposed to my earlier “jumping the snark”) correct my understanding here if necessary: if the moisture is not there nor the temperature differential, no natural amount of aerosol will trigger significant precipitation? On the other hand, in the presence of ordinary (“natural”) levels of aerosols, air that is unusually saturated with moisture that encounters relatively cooler air will be far more likely to produce extreme precipitation (the moisture has to be there). I.e., ceteris paribus:

    Warm(er) moist(er) air encountering cool(er) air is far more likely to produce extreme precipitation than one would otherwise expect were less warm, less moist air to encounter equally cooler air? And one would expect that moisture to be more likely to come out (again, ceteris paribus) upon encountering relatively cooler air, as opposed to air of the same approximate temperature? Is there an algorithmically stable trade-off between temperature levels and aerosol content? I.e., can “we” track in a fairly direct manner the likelihood of precipitation against varying levels of temperature and aerosol differentials between moisture laden air and that which it is encountering? (I think I might be asking for a citation to a good meterology textbook.)

    (By the bye: I did not mention aerosols in my earlier post but, given the ceteris paribus, any reason to believe natural levels of aerosols over the midwest and its relevant feeder rivers and tributaries, have shifted significantly of late? Particularly since the near term results of the air quality legislation of the ’70’s led to a significant reduction of non-natural contributions?)

  12. David B. Benson says:

    Gary Herstein — Essentially everything I know about the process comes from Ray Pierrehumbert’s

    and his paper (with co-authors) with the pdf filename of CaltechWater.pdf.

    If aerosols, dust, bactria, whathaveyou, is not present, the clouds, which have already condensed out of the air, cannot form percipitation. There may be aspects of temperature and pressure involved as well, but I don’t know.

    So first clouds are required. A mass of air, containing water vapor, is lifted aloft by one or another process, usually convection. As it rises it becomes less dense and cooler. Eventually it becomes so undense and cool that some of the water vapor condenses into clouds.

    The clouds may persist or become precipitation. Locally, either may happen, with more clouds and more precipitation at the higher elevations to the east.

    Globally, it seems that precipitation has not changed in 28 years, but there is somewhat more than 52 years ago. I’m under the impression (perhaps mistaken) that the cloudiness hasn’t changed much.

    For any more details, you’ll need a better source.

  13. Paul K says:

    Gary Herstein,
    I’m going to assume you haven’t spent a lot of time in the Midwest. It floods here every spring. Listen to what David is saying. Global precipitation has not changed during the period of most intense warming. This year’s Midwest rains are not out of the ordinary. There is no link to global warming.

  14. Joe says:

    Paul — I’m afraid you are wedded to an increasingly absurdist position.

    This was a 500-year flood, much as 1993 was. How is that possible? it’s called climate change.

    In fact, as this very report shows, there has been any clearer increase in intense rain fall during the. Most intense warming.

  15. David B. Benson says:

    Paul K — What is predicted (and is increasingly observed) is that with global warming it will be wetter where it is wet and dryer where it is dry.

    Alsao, the longer range prediction is for more, on average, precipitation. Much of that increase will simply fall back into the oceans.

  16. Paul K says:

    In the report – and no, I have not closely read all 180 pages – it looks like most of the precipitation data data is post 1895 and some is post 1950. Seems a short time scale to come to a definitive conclusion. On the other hand, there’s an interesting tree ring based chart (chapter 2 fig. 2.7) showing Western U.S. drought over the last 1,200 years. It does not appear the dry is getting dryer just yet.

  17. Gary Herstein says:

    My thanks to David for the citation (and apologies for taking so long to get say as much — I should have known better than to post just as I was moving.)

    To Paul K, along with Joe’s comment, the bit about two “500 year floods” in just 15 years seems a bit telling.

    On the other hand I just moved back to the midwest from Ohio. Besides the decades that I have lived here, I know more than a few people who’ve been here there entire (50+ yr) lives. All of which is perfectly irrelevant, which is perfectly obvious to anyone with even a little background in logic, because it is an appeal to annecdotal evidence. Since you would seem to hold yourself up as an exemplar of logical reasoning, it rather beggars the imagination why you would presume to stoop to such a cheap rhetorical stunt.