Explaining NOAA’s “No More Hiatus” Paper

October 30, 2015


In summary, newly corrected and updated global surface temperature data from NOAA’s NCEI do not support the notion of a global warming “hiatus.”

Karl et al Possible artifacts of data biases in the recent global surface warming hiatus

For a better understanding of the paper at the center of the House Science Committee/NOAA kerfuffle – no better person than Dana Nuccitelli at Skeptical Science, followed by John Abraham in the Guardian.

Last week, a paper out of NOAA concluded that contrary to the popular myth, there’s been no pause in global warming. The study made headlines across the world, including widely-read Guardian stories by John Abraham and Karl Mathiesen. In fact, there may have been information overload associated with the paper, but the key points are relatively straightforward and important.

1. Rapid Global Warming Continues

Arguments about short-term temperature changes only deal with the Earth’s surface temperatures, which account for just 1–2% of the overall warming of the planet. More than 90% of that heat goes into the oceans, and as my colleagues and I noted in a paper published 3 years ago, if anything that warming is accelerating, building up heat at a rate faster than 4 atomic bomb detonations per second.

If you carefully cherry pick start and end dates, you can find a period around 1998–2012 during which the warming of surface temperatures slowed a bit due to temporary natural cooling factors (like more La Niñas), just like it sped up a bit during the 1990s due to temporary natural warming factors (like more El Niños). But these are just wiggles on top of the long-term human-caused global warming trend. As Michael Mann put it,

there never was any “pause” or “hiatus” in global warming. There is evidence, however, for a modest, temporary slowdown in surface warming through the early part of this decade.

2. The Surface Warming Slowdown is Probably Over

This is a tough pill to swallow for those who have misused the short-term slowdown in global surface warming to argue against climate policies, but it’s likely over. 2014 was the hottest year on record, and 2015 looks likely to break the record again.

These slowdown-based anti-policy arguments have been made by everyone fromRepublican presidential candidates to political think tanks to science-denying blogs. It’s a simple argument – if we pretend the surface warming slowdown can continue indefinitely, then global warming is less of a concern and we don’t need policies to stop it.

Since we’ve always known the slowdown was temporary, these were never credible arguments, but they nevertheless helped to delay efforts to curb global warming. After the publication of this NOAA paper, and possibly two consecutive record hot years, it seems unlikely that these arguments will be considered credible any longer.

3. The Most Common Denial Response: Conspiracy Theories

Social science research has shown that conspiracy theorists are more likely to reject scientists’ conclusions about climate change. It’s a logical connection – given that 97% of climate scientists and their research agree on human-caused global warming, the easiest way to deny that reality is to accuse all those scientists of being part of a vast conspiracy. Otherwise it’s difficult to justify rejecting the conclusions of 97% of experts.

Thus it’s not surprising that those in denial are accusing the NOAA scientists of conspiring to fudge the data to make the slowdown disappear. For example, Anthony Watts, who runs a climate science denial blog, wrote an email to one of the authors of the NOAA paper, telling him,

In my last telephone conversation with you, I stated (paraphrasing) that “I believe you folks aren’t doing anything fraudulent, but you are doing what you feel is correct science in what you believe is a correct way”.

After seeing the desperate tricks pulled in Karl 2015 to erase “the pause” via data manipulation, I no longer hold that opinion. You needed it to go away, so you prostituted yourselves, perhaps at the direction of higher ups.

In fact, accusing the NOAA scientists of fraudulently ‘manipulating data’ for the benefit of the Obama administration was a common theme in the climate science-denying blogosphere. But there’s a glaring flaw in this particular conspiracy theory.

4. The Adjustments Reduce Global Warming!

This is clear from the bottom frame in this figure in the NOAA paper.

fig 2

NOAA global surface temperature changes with new analysis, old analysis, and with and without time-dependent bias corrections. (A) The new analysis (solid black) compared to the old analysis (red). (B) The new analysis (solid black) versus no corrections for time-dependent biases (cyan). Source: Science; Karl et al. (2015) 

According to the raw, unadjusted data, global surface temperatures warmed about 0.9°C from 1880 to 2014. According to the new NOAA analysis, they warmed about 0.8°C during that time. That’s a bit more than in the previous version of NOAA’s data set (0.75°C), but the net effect of these adjustments is to reduce the overall estimated warming as compared to the raw data!

5. The Adjustments are Important

Contrary to the conspiracy theories, climate scientists process the raw temperature data for an important reason – to remove biases that don’t represent real temperature changes. The big one in the new NOAA analysis deals with changes in the ways ocean temperatures have been measured. They’ve been measured from water samples in insulated buckets, uninsulated buckets, from valves in ships’ hulls, and from instruments on buoys. As Zeke Hausfather explains,

A number of studies have found that buoys tend to measure temperatures that are about 0.12°C colder than is found by ships at the same time and same location. As the number of automated buoy instruments has dramatically expanded in the past two decades, failing to account for the fact that buoys read colder temperatures ended up adding a negative bias in the resulting ocean record. This change is by far the largest single factor responsible for changing global temperatures in the past 17 years compared to temperatures found in the prior NOAA record.

While this adjustment happens to have reduced estimates of the 1998–2012 surface warming slowdown, it’s important to account for changes in the way ocean temperatures have been measured. It’s not a conspiracy, it’s science.

John Abraham in the Guardian:

The scientists make a number of improvements upon existing information. First, they focus on ocean surface temperature measurements from floating buoys and from ship-board sensors. We know that temperatures measured by ship sensors are often warmer than temperatures measured by buoys, in part because of the heat generated by the ship engine. A more thorough accounting of this effect has been implemented in the Extended Reconstructed Sea Surface Temperature data set version 4. This accounting is utilized in the paper.

Second, there has been a historical change in how ships measure surface temperatures. Decades ago, temperatures were mainly measured by insulated buckets. Around the time of World War 2, there was a change from insulated buckets to temperature sensors contained within ship hulls. The ship hull sensors recorded warmer water temperatures compared to the bucket method. A more thorough handling of the changes from buckets to ship hull sensors was also included in the new paper.

Finally, the new study used more recent estimates of the land temperatures. The new estimates combine multiple temperature databases into a single integrated whole.

The end result is that the temperature trends over the past 17 or so years has continued to increase with no halt. In fact, it has increased at approximately the same rate as it had for the prior five decades. But the authors went further by trying to cherry-pick the start and end dates. For instance, they stacked the cards against themselves by purposefully picking a very hot year to start the analysis and a cool year to terminate the study (1998 and 2012, respectively). Even this cherry-picked duration showed a warming trend. Furthermore, the warming trend was significant.

I asked lead author Dr. Karl for his comments on the significance of the paper and he told me,

Considering all the short-term factors identified by the scientific community that acted to slow the rate of global warming over the past two decades (volcanoes, ocean heat uptake, solar decreases, predominance of La Niñas, etc.) it is likely the temperature increase would have accelerated in comparison to the late 20th Century increases. Once these factors play out, and they may have already, global temperatures could rise more rapidly than what we have seen so far.

3 Responses to “Explaining NOAA’s “No More Hiatus” Paper”

  1. redskylite Says:

    The hiatus was a myth first propagated by David Rose aided by Judith Curry in the tabloid “Daily Mail”.

    It is sad that it has taken so much time to repudiate it. Gullible people, conned by the media and more valuable years of inaction wasted.

    Meanwhile studies report that temperatures will not be survivable in parts of the middle east. Bedouins and other nomads living in tents do not luxuriate in Air Conditioning.

    Don’t believe in your own academics … ?

    Lets go at swat team pace.. People will perish . . .

    Humble, simple and good people . . . . .

  2. j4zonian Says:

    “…these were never credible arguments, but they nevertheless helped to delay efforts to curb global warming. After the publication of this NOAA paper, and possibly two consecutive record hot years, it seems unlikely that these arguments will be considered credible any longer.”

    There’s nothing there explaining why people would stop believing incredible things they have always believed just because they’ve been shown, for the seven hundred thousandth time, to be incredible.

    Anyone who’s ever talked to denying delayalists knows many of those who are left now will simply become more certain than ever that there’s a conspiracy and data is being manipulated, even falsified, to support the conspiracy’s claim of warming.

    Please, we need to consider not just the physics and chemistry here but the science of psychology. which at this point is much more important in helping us make the changes we need to make in the way we live in order to avoid cataclysm. Many people have made efforts to learn the science of climate catastrophe, and that’s been a boon to civilization in many ways. We all need to learn much, much more about psychology now, not only to help eliminate denial but to learn why we’re in this larger social-political-ecological crisis in the first place, so we can fix the psychological problems that have created the whole mess.

    • dumboldguy Says:

      Here’s Jeffy, once again displaying his ignorance of science by pontificating about the “science of psychology” and how it is the “solution” to dealing with CAGW. Hate to disabuse you, Jeffy, but psychology is NOT a science. Those of us who have studied in both psychology and the “pure” sciences know that, why don’t you?

      He also displays his naivete by suggesting we can “fix” the “psychological problems that have created the whole mess”. Nice sounding BS, Jeffy—-did it come out of one of your mediation circles?—-the same one where you decided some of us needed “healing”?

      As I said on another thread, Jeffy is stuck in Kubler-Ross stage one—-denial—-fueled by his narcissistic belief in his uneducated opinions. And that’s too bad, because until he becomes educated enough on the “science-social-political-economic-ecological-psychological-existential crisis” he will remain there and we will have to listen to his BS.

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