The source? “Possible artifacts of data bias in the recent global surface warming hiatus,” published this week in Science, by long-time global warming alarmist Tom Karl et al.
Much study has been devoted to the possible causes of an apparent decrease in the upward trend of global surface temperatures since 1998, a phenomenon that has been dubbed the global warming “hiatus.” Here we present an updated global surface temperature analysis that reveals that global trends are higher than reported by the IPCC, especially in recent decades, and that the central estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a “slowdown” in the increase of global surface temperature.
Proper first impression response (though I confess it didn’t dawn on me first thing): “These results do not support …” does not entail that no other results do. I could study the colors of cats’ eyes in my neighborhood and conclude, “These results to not support the notion of a ‘slowdown’ in the increase of global surface temperature.”
That conclusion would be true. But it would also be irrelevant to the question whether “the pause” is real.
Imagine for a moment that you’re investigating the question, “Is there an elephant in the house?” It’s a nine-room house. Each of eight investigators finds an elephant in a different one of eight rooms. Eight rooms, eight elephants. But one investigator finds no elephant in the bathroom. Would you conclude from his finding, “No elephant in the house”?
So the crucial, first question we should ask is, Do other results support the notion of a ‘slowdown’ in the increase of global surface temperature? And the answer is Yes!
But I’ll go there in a moment. First a quick list of early critiques of Karl et al.’s article. Within a day or two of its appearance, the following critical articles had already appeared.
The most technical was Ross McKitrick’s “A first look at ‘Possible artifacts of data bias in the recent global surface warming hiatus’ by Karl et al. Science 4 June 2015. McKitrick begins (perhaps having thought of the point I just made about “These results do not support …”) by listing eight datasets that do “support the notion of a ‘slowdown’ in the increase of global surface temperature:”:
(HadCRUT [land surface and ocean]; HadSST [ocean surface only]; NCDC [land surface and ocean]; GISS [land surface and ocean]; RSS satellite [lower troposphere]; UAH satellite [lower troposphere]; Ocean heat content 0-2000 meter [Argo floats]; and NOAA SST estimates). He provides nice graphs of all seven and points out all kinds of statistical and data-quality problems in the article to conclude:
Are the new K15 adjustments correct? Obviously it is not for me to say – this is something that needs to be debated by specialists in the field. But I make the following observations:
* All the underlying data (NMAT, ship, buoy, etc) have inherent problems and many teams have struggled with how to work with them over the years
* The HadNMAT2 data are sparse and incomplete. K15 take the position that forcing the ship data to line up with this dataset makes them more reliable. This is not a position other teams have adopted, including the group that developed the HadNMAT2 data itself.
* It is very odd that a cooling adjustment to SST records in 1998-2000 should have such a big effect on the global trend, namely wiping out a hiatus that is seen in so many other data sets, especially since other teams have not found reason to make such an adjustment.
* The outlier results in the K15 data might mean everyone else is missing something, or it might simply mean that the new K15 adjustments are invalid.
It will be interesting to watch the specialists in the field sort this question out in the coming months.
Likely to be the most troubling to the climate alarmist establishment (because she’s the least identified as a “denier”) so far is Judith Curry’s “Has NOAA ‘busted’ the pause in global warming?”
She points out that the datasets on which Karl et al. rely have greater uncertainties than others that they purport to correct. She then writes,
“My bottom line assessment is this. I think that uncertainties in global surface temperature anomalies is substantially understated. The surface temperature data sets that I have confidence in are the UK group and also Berkeley Earth. This short paper in Science is not adequate to explain and explore the very large changes that have been made to the NOAA data set. The global surface temperature datasets are clearly a moving target. So while I’m sure this latest analysis from NOAA will be regarded as politically useful for the Obama administration, I don’t regard it as a particularly useful contribution to our scientific understanding of what is going on.”
Cato’s Big Three
Patrick Michaels, Richard Lindzen, and Paul C. Knappenberger take on Karl et al. in “@NOAA’s desperate new paper: Is there no global warming ‘hiatus’ after all?” They begin with what ought to be an obvious point but in our innumerate society (and it’s amazing how many scientists, even, are innumerate, not in that they don’t know how to do complicated math but in that they forget basic math principles, like statistical significance levels, especially when forgetting serves their purposes):
The main claim by the authors that they have uncovered a significant recent warming trend is dubious. The significance level they report on their findings (.10) is hardly normative, and the use of it should prompt members of the scientific community to question the reasoning behind the use of such a lax standard.
Then they point out various weaknesses in the reliability of the data on which Karl et al. rely. They conclude:
[E]ven presuming all the adjustments applied by the authors ultimately prove to be accurate, the temperature trend reported during the “hiatus” period (1998-2014), remains significantly below (using Karl et al.’s measure of significance) the mean trend projected by the collection of climate models used in the most recent report from the United Nation’s Intergovernmental Panel on Climate Change (IPCC). It is important to recognize that the central issue of human-caused climate change is not a question of whether it is warming or not, but rather a question of how much. And to this relevant question, the answer has been, and remains, that the warming is taking place at a much slower rate than is being projected.
That’s an important point. The climate models are the only grounds for fearing dangerous manmade warming. The eight more commonly used datasets show that they grossly exaggerate CO2’s warming effect. Karl et al.’s fiddled–er, reconstructed–dataset only shows that they somewhat less grossly exaggerate. That’s not exactly a ringing vindication. It still leaves us with no rational basis to fear dangerous warming, and so no rational basis for policy to mitigate it.
Bob Tisdale and Anthony Watts take on the new study in the aptly titled “NOAA/NCDC’s new ‘pause-buster’ paper: A laughable attempt to create warming by adjusting past data.” In addition to pointing out all kinds of uncertainties about the datasets on which Karl et al. rely–uncertainties much greater than those that show the “pause”–they point out that Karl et al. choose 1951 to 2012 and 1950 to 1999 as the reference period against which to compare the period of the alleged pause.
But of course, there was significant global cooling going on in the 1950s through early 1970s–enough to cause panic about a coming ice age. As Tisdale and Watts say, “If NOAA would like to revise their estimates of future global warming to reflect the more benign warming rate of 0.1 deg C/decade from 1950 to 1999, it would be a big step toward their coming to terms with reality.” Right. That would be essentially cutting IPCC’s estimates of CO2-induced warming by a third, which would put NOAA and Karl et al. solidly in the camp of–horror of horrors!–AGW deniers!
Global Warming Policy Foundation
The Global Warming Policy Foundation chimes in with “Reports of the death of the global warming pause are greatly exaggerated.” (Hat tip to Mark Twain.) The article summarizes “Key pitfalls” of Karl et al.’s paper thus:
“The authors have produced adjustments that are at odds with all other surface temperature datasets, as well as those compiled via satellite.”
“They do not include any data from the Argo array that is the world’s best coherent data set on ocean temperatures.”
“Adjustments are largely to sea surface temperatures (SST) and appear to align ship measurements of SST with night marine air temperature (NMAT) estimates, which have their own data bias problems.”
“The extend of [sic; They extend?] the largest SST adjustment made over the hiatus period, supposedly to reflect a continuing change in ship observations (from buckets to engine intake thermometers) is not justified by any evidence as to the magnitude of the appropriate adjustment, which appears to be far smaller.”
Then they expand on those in eight numbered points and conclude:
This is a highly speculative and slight paper that produces a statistically marginal result by cherry-picking time intervals, resulting in a global temperature graph that is at odds with those produced by the UK Met Office and NASA. Caution and suitable caveats should be used in using this paper as evidence that the global annual average surface temperature ‘hiatus’ of the past 18 years has been explained.
Not to be left out, the inimitable Lord Christopher Monckton weighs in with “Has NOAA/NCDC’s Tom Karl repealed the laws of thermodynamics?” He begins with a humorous rehearsal of a Congressional committee hearing at which both he and Karl were expert witnesses and he had shown that global average temperature had actually been falling for the past eight years, which Karl contested but the data showed true, and that hurricane frequencies hadn’t risen in 100 years, which Karl challenged, whipping out a chart that to his horror showed that Monckton was indeed wrong–they actually hadn’t risen for the last 150 years.
The history is entertaining, and I can vouch for its general accuracy–I was there, as another expert witness. Then Monckton zeroes in on the topic suggested by his title. Even assuming Karl et al.’s temperature reconstruction is right, the resulting scenario is that the ocean near-surface temperatures rose at a rate that would require considerable movement of heat into that region from above or below, but neither the troposphere nor the deep ocean showed sufficient warming to be the origin of that migrating heat.
Hence, for Karl et al.’s scenario to be accurate, we must assume, as I shall here try to summarize as concisely and simply as I can, that heat radiated, both upward and downward, from cooler to warmer masses, which conflicts with the laws of thermodynamics.
Meanwhile, what seems to me about the most obvious response is this: We should keep comparing apples and apples as much as possible.
The most reliable global temperature data from 1979 to the present come from satellites. They are least subject to local contamination, sample change or inadequacy, and variation in method and instrumentation over time. And they show, as Monckton points out in “El Nino strengthens: the Pause lengthens,” that “For 222 months, since December 1996, there has been no global warming at all (Fig. 1).
“This month’s RSS temperature – still unaffected by a slowly strengthening el Niño, which will eventually cause temporary warming – passes another six-month milestone, and establishes a new record length for the Pause: 18 years 6 months.”
Wall Street Journal Again
By the way, keep in mind the psychological effect of the WSJ headline: “Study finds no pause in global warming.” That sounds so conclusive! But had WSJ reported on the last-cited article, which appeared at essentially the same time as NOAA’s, it could have run the headline “Study finds pause in global warming.”
Indeed, WSJ could have run the two stories exactly parallel to each other on the same day.
No single study settles a matter. And finding no elephant in the bathroom does not mean there’s none in the living room.