My op-ed in the Wall Street Journal addresses the latest explanations for the "pause" in global warming and their implications. I have responded to an ill-informed critique of the article below.
On Sept. 23 the United Nations will host a party for world leaders in New York to pledge urgent action against climate change. Yet leaders from China, India and Germany have already announced that they won't attend the summit and others are likely to follow, leaving President Obama looking a bit lonely. Could it be that they no longer regard it as an urgent threat that some time later in this century the air may get a bit warmer?
In effect, this is all that's left of the global-warming emergency the U.N. declared in its first report on the subject in 1990. The U.N. no longer claims that there will be dangerous or rapid climate change in the next two decades. Last September, between the second and final draft of its fifth assessment report, the U.N.'s Intergovernmental Panel on Climate Change quietly downgraded the warming it expected in the 30 years following 1995, to about 0.5 degrees Celsius from 0.7 (or, in Fahrenheit, to about 0.9 degrees, from 1.3).
Even that is likely to be too high. The climate-research establishment has finally admitted openly what skeptic scientists have been saying for nearly a decade: Global warming has stopped since shortly before this century began.
First the climate-research establishment denied that a pause existed, noting that if there was a pause, it would invalidate their theories. Now they say there is a pause (or "hiatus"), but that it doesn't after all invalidate their theories.
Alas, their explanations have made their predicament worse by implying that man-made climate change is so slow and tentative that it can be easily overwhelmed by natural variation in temperature—a possibility that they had previously all but ruled out.
When the climate scientist and geologist Bob Carter of James Cook University in Australia wrote an article in 2006 saying that there had been no global warming since 1998 according to the most widely used measure of average global air temperatures, there was an outcry. A year later, when David Whitehouse of the Global Warming Policy Foundation in London made the same point, the environmentalist and journalist Mark Lynas said in the New Statesman that Mr. Whitehouse was "wrong, completely wrong," and was "deliberately, or otherwise, misleading the public."
We know now that it was Mr. Lynas who was wrong. Two years before Mr. Whitehouse's article, climate scientists were already admitting in emails among themselves that there had been no warming since the late 1990s. "The scientific community would come down on me in no uncertain terms if I said the world had cooled from 1998," wrote Phil Jones of the University of East Anglia in Britain in 2005. He went on: "Okay it has but it is only seven years of data and it isn't statistically significant."
If the pause lasted 15 years, they conceded, then it would be so significant that it would invalidate the climate-change models upon which policy was being built. A report from the National Oceanic and Atmospheric Administration (NOAA) written in 2008 made this clear: "The simulations rule out (at the 95% level) zero trends for intervals of 15 yr or more."
Well, the pause has now lasted for 16, 19 or 26 years—depending on whether you choose the surface temperature record or one of two satellite records of the lower atmosphere. That's according to a new statistical calculation by Ross McKitrick, a professor of economics at the University of Guelph in Canada.
It has been roughly two decades since there was a trend in temperature significantly different from zero. The burst of warming that preceded the millennium lasted about 20 years and was preceded by 30 years of slight cooling after 1940.
This has taken me by surprise. I was among those who thought the pause was a blip. As a "lukewarmer," I've long thought that man-made carbon-dioxide emissions will raise global temperatures, but that this effect will not be amplified much by feedbacks from extra water vapor and clouds, so the world will probably be only a bit more than one degree Celsius warmer in 2100 than today. By contrast, the assumption built into the average climate model is that water-vapor feedback will treble the effect of carbon dioxide.
But now I worry that I am exaggerating, rather than underplaying, the likely warming.
Most science journalists, who are strongly biased in favor of reporting alarming predictions, rather than neutral facts, chose to ignore the pause until very recently, when there were explanations available for it. Nearly 40 different excuses for the pause have been advanced, including Chinese economic growth that supposedly pushed cooling sulfate particles into the air, the removal of ozone-eating chemicals, an excess of volcanic emissions, and a slowdown in magnetic activity in the sun.
The favorite explanation earlier this year was that strong trade winds in the Pacific Ocean had been taking warmth from the air and sequestering it in the ocean. This was based on a few sketchy observations, suggesting a very tiny change in water temperature—a few hundredths of a degree—at depths of up to 200 meters.
Last month two scientists wrote in Science that they had instead found the explanation in natural fluctuations in currents in the Atlantic Ocean. For the last 30 years of the 20th century, Xianyao Chen and Ka-Kit Tung suggested, these currents had been boosting the warming by bringing heat to the surface, then for the past 15 years the currents had been counteracting it by taking heat down deep.
The warming in the last three decades of the 20th century, to quote the news release that accompanied their paper, "was roughly half due to global warming and half to the natural Atlantic Ocean cycle." In other words, even the modest warming in the 1980s and 1990s—which never achieved the 0.3 degrees Celsius per decade necessary to satisfy the feedback-enhanced models that predict about three degrees of warming by the end of the century—had been exaggerated by natural causes. The man-made warming of the past 20 years has been so feeble that a shifting current in one ocean was enough to wipe it out altogether.
Putting the icing on the cake of good news, Xianyao Chen and Ka-Kit Tung think the Atlantic Ocean may continue to prevent any warming for the next two decades. So in their quest to explain the pause, scientists have made the future sound even less alarming than before. Let's hope that the United Nations admits as much on day one of its coming jamboree and asks the delegates to pack up, go home and concentrate on more pressing global problems like war, terror, disease, poverty, habitat loss and the 1.3 billion people with no electricity.
Post-script. After the article was published, an astonishing tweet was sent by the prominent economist Jeffrey Sachs saying
"Ridley climate ignorance in WSJ today is part of compulsive lying of Murdoch media gang. Ridley totally misrepresents the science."
Curious to know how I had lied or "totally misrepresented" the science, I asked Sachs to explain. There was a deafening silence.
There then appeared at the Huffington Post (a media outlet owned by a person with strong views, by the way) an article under Sachs's name. Its style was quite unlike that of Sachs, and strongly resembled the style and debating technique of a spin doctor employed by Lord Stern at the London School of Economics, who writes to newspapers furiously denouncing the author of any article on climate change that he does not like. Indeed that same spin doctor, Bob Ward, alerted me to the Huff Post article in a tweet. The piece purported to -- in the spin doctor's words -- expose
"The Wall Street Journal Parade of Climate Lies - @JeffDSachs destroys daft @mattwridleyarticle in@WSJ".
However, it does nothing of the sort. It's all bluster and careful misdirection, and contradicts nothing in my article, let alone producing evidence against of lies. Paragraph by paragraph, I will expose its daftness, which truly shocked me given that I had respect for Jeffrey Sachs as a scholar before reading this. Here are the key paragraphs:
Ridley's "smoking gun" is a paper last week in Science Magazine by two scientists Xianyao Chen and Ka-Kit Tung, which Ridley somehow believes refutes all previous climate science. Ridley quotes a sentence fragment from the press release suggesting that roughly half of the global warming in the last three decades of the past century (1970-2000) was due to global warming and half to a natural Atlantic Ocean cycle. He then states that "the man-made warming of the past 20 years has been so feeble that a shifting current in one ocean was enough to wipe it out altogether," and "That to put the icing on the case of good news, Xianyao Chen and Ka-Kit Tung think the Atlantic Ocean may continue to prevent any warming for the next two decades."
Notice the quote marks around "smoking gun", implying that I used the phrase. I did not. In any case, the Chen and Tung paper was only one of the pieces of evidence I cited.
The Wall Street Journal editors don't give a hoot about the nonsense they publish if it serves their cause of fighting measures to limit human-induced climate change. If they had simply gone online to read the actual paper, they would have found that the paper's conclusions are the very opposite of Ridley's.
In his writing the real Mr Sachs does not often use phrases like "don't give a hoot".
In any case, he's plain wrong about the contradiction. The quote I gave from the press release is accurate. And I have read the paper and can assure Mr "Sachs" that its conclusions are not the opposute of what I have said. As further confirmation, how about asking the paper's lead author himself? This is what he wrote to Professor Judith Curry in response to her questions:
The argument on the roughly 50-50 attribution of the forced vs unforced warming for the last two and half decades of the 20th century is actually quite simple. If one is blaming internal variability for canceling out the anthropogenically forced warming during the current hiatus, one must admit that the former is not negligible compared to the latter, and the two are probably roughly of the same magnitude. Then when the internal cycle is of the different sign in the latter part of the 20th century, it must have added to the forced response. Assuming the rate of forced warming has not changed during the period concerned, then the two combined must be roughly twice the forced warming during the last two and half decades of the 20th century.
In other words, as I said, the warming of 1975-2000 was only half caused by man-made emissions and half by natural causes, and natural causes were enough to cancel man-made forcing in the years after 2000.
To continue with the "Sachs" article:
First, the paper makes perfectly clear that the Earth is warming in line with standard climate science, and that the Earth's warming is unabated in recent years. In the scientific lingo of the paper (it's very first line, so Ridley didn't have far to read!), "Increasing anthropogenic greenhouse-gas-emissions perturb Earth's radiative equilibrium, leading to a persistent imbalance at the top of the atmosphere (TOA) despite some long-wave radiative adjustment." In short, we humans are filling the atmosphere with carbon dioxide from fossil-fuel use, and we are warming the planet.
Mr "Sachs" did not have far to read in my own article to find this is in complete agreement with what I wrote also:
I've long thought that man-made carbon-dioxide emissions will raise global temperatures, but that this effect will not be amplified much by feedbacks from extra water vapor and clouds, so the world will probably be only a bit more than one degree Celsius warmer in 2100 than today.
Instead of using words like "unabated" why not give numbers? I did.
The warming during 1975-2000, even if you cherry-pick the end points, was about 0.4 degrees C if you average the five main global data sets, and if half of that was natural, then man-made forcing was going at the rate of less than 1 degree per century, rather less than what i said.
Second, the total warming is distributed between the land and ocean surface on the one hand and the ocean deep water on the other. The total rise of ocean heat content has continued unabated, while the proportion of heat absorbed at the surface and in the deeper ocean varies over time. Again, in the scientific lingo of the paper, "[T]his forced total OHC [ocean heat content] should be increasing monotonically over longer periods even through the current period of slowed warming. In fact, that expectation is verified by observation ...". In other words, the ocean has continued to warm in line with predictions of just such a phenomenon seen in climate models.
This is highly misleading. Yes, as I clearly stated in my article, the ocean could start to transfer heat to the air again. So the quote from the paper does not contradict me at all. In any case, remember, the data on ocean heat content is highly ambiguous. As Judith Curry summarised it recently:
The main issue of interest is to what extent can ocean heat sequestration explain the hiatus since 1998. The only data set that appears to provide support for ocean sequestration is the ocean reanalysis, with the Palmer and Domingues 0-700 m OHC climatology providing support for continued warming in the upper ocean.
All in all, I don’t see a very convincing case for deep ocean sequestration of heat. And even if the heat from surface heating of the ocean did make it into the deep ocean, presumably the only way for this to happen involves mixing (rather than adiabatic processes), so it is very difficult to imagine how this heat could reappear at the surface in light of the 2nd law of thermodynamics.
Back to the Sachs article:
Third, it is the "vertical distribution" of the warming, between the surface and deep water, which affects the warming observed on land and at the sea surface. The point of the paper is that the allocation of the warming vertically varies over time, sometimes warming the surface rapidly, other times warming the deeper ocean to a great extent and the surface water less rapidly. According to the paper, the period of the late 20th century was a period in which the surface was warmed relative to the deeper ocean. The period since 2000 is the opposite, with more warming of the deeper ocean. How do the scientists know? They measure the ocean temperature at varying depths with a sophisticated system of "Argo profiling floats," which periodically dive into the ocean depths to take temperature readings and resurface to transmit them to the data centers.
I have no problem with this paragraph, which merely reiterates what i said about the Chen and Tung paper, with a bit more detail about the Argo floats etc.
So, what is Ridley's "smoking gun" when you strip away his absurd version of the paper? It goes like this. The Earth is continuing to warm just as greenhouse gas theory holds.
Check, I agree. But the atmosphere is not continuing to warm right now.
The warming heats the land and the ocean. The ocean distributes some of the warming to the surface waters and some to the deeper waters, depending on the complex circulation of ocean waters.
Check. Could not have said it better myself.
The shares of warming of the surface and deeper ocean vary over time, in fluctuations that can last a few years or a few decades.
Where's the contradiction with what i wrote? There is none. If Mr "Sachs" had bothered to read my article properly, he would find that his description of what is happening is pretty well exactly the same as mine. Except that he gives no numbers. What I did was to show that if Chen and Tung is right, and half the warming in the last part of the last century was natural, then the "rapid" warming of those three decades, was still too slow for the predictions made by the models, will if it resumes give us a not very alarming future. And if it does not resume for some time, as Chen and Tung speculate that it might not, then the future is even less alarming.
And no, again, I did not use the phrase "smoking gun". I used several other arguments, all of which Mr "Sachs" fails to address at all, so presumably he agrees that there has been a "pause", that it was denied for many years by the climate establishment, that there was general agreement among them that a pause of more than 15 years would invalidate their models, and so on.
He goes on:
If the surface warming is somewhat less in recent years than in the last part of the 20th century, is that reason for complacency? Hardly. The warming is continuing, and the consequences of our current trajectory will be devastating unless greenhouse gas emissions (mainly carbon dioxide) are stopped during this century. As Chen and Tung conclude in their Science paper, "When the internal variability [of the ocean] that is responsible for the current hiatus [in warming] switches sign, as it inevitably will, another episode of accelerated global warming should ensue."
I hardly think it was complacent of me to ask world leaders to address the much more urgent issues of war, terror, disease, poverty, habitat loss and the 1.3 billion people with no electricity.
Again, i said, that warming may well resume. The only disagreement is whether it will be devastating, and that is a prediction not an empirical fact. I cannot yet be "wrong" about it.
When, Oh when, will Mr "Sachs" get around to including a number, any number. He surely cannot be under the impression that lukewarmers like me think there is no greenhouse effect? He surely knows that the argument is not about whether there is warming, but how fast.
And where did I lie, or misrepresent? Where, Mr Ward, did he "destroy" me, pray? He did not.
Mr "Sachs", who is usually a careful academic, has published a lot of wild accusations against me and "totally" (his word) failed to stand them up. How did this come about? Perhaps, being a busy man, he asked somebody else to ghost-write much of the piece for him and did not check it very thoroughly. If so, no problem, a quick tweet apologising to me and admitting that nothing in his article contradicts anything in mine, that we merely disagree on the predictions of dangerous warming, and I will consider the matter closed.
Matt Ridley, a member of the British House of Lords, is an acclaimed author who blogs at www.rationaloptimist.com.
Matt Ridley, a member of the British House of Lords, is an acclaimed author who blogs at www.rationaloptimist.com.