The latest myth making the rounds among climate-change deniers is that reports of a "global warming hiatus" are proof that climate prediction models are flawed. The global temperature, they say, hasn't increased in nearly 20 years. As usual, they're getting it wrong.
Although the rate of increase in the globally and annually averaged temperature of the atmosphere near the surface has slowed since around 2000 compared to the rate of increase over the preceding three decades, near-surface warming of the atmosphere has continued. The 2000s were warmer than the 1990s, and the 2010s so far have been warmer than the 2000s.
But, climate-change deniers interpret this to mean that the temperature hasn't changed since 1998. Yesterday, at a House Science, Space, and Technology Committee hearing on the Obama administration's plan to fight climate change, Rep. Larry Bucshon (R-IN) lectured White House Science Adviser John Holdren:
"Over the last few years, we've gone from global warming to climate change since the temperature hasn't changed in many, many years. The temperature or the earth has been changing for centuries. I fully believe that the temperature is changing. But of course now supporters of this new regulation are saying 'Well, it's changing now at an unusual pace compared to the past,' because now the American public is getting it that the temperature of the earth has been changing for centuries."
Of course, nobody in the scientific community denies that the temperature of the Earth has always been changing (and for a hell of a lot longer than "centuries"). Nor do they deny that there will be variations in that change.
As Holdren himself noted in his prepared testimony:
The long-term warming trend resulting from the build-up of heat-trapping gases and particles in the atmosphere is superimposed on a considerable amount of variability—year-to-year and decade-to-decade ups and downs in the global-average atmospheric temperature resulting from variations in solar output, in volcanic activity that injects reflecting particles into the stratosphere, and in ocean circulation patterns that govern how much of the trapped heat goes into the oceans as opposed to staying in the atmosphere.
Scientists do not expect the rate of atmospheric warming, which results from the combination of human and natural influences, to be uniform from year to year and decade to decade. Climate models show short periods of slow warming and even cooling within long-term warming epochs, much as we see recently in observations.
Buschon also believes this is further evidence that this is a moneymaking scam among scientists. Again, at yesterday's hearing, Bucshon asked Holdren whether it was true that the EPA's regulations for coal plants would have no impact on reducing global temperature:
Bucshon: Is it true that this rule has no effect on the global temperature change?
Holdren: Can I take that? I'd like to respond to that.
Bucshon: There's public comment out there that that question has been asked and answered saying no.
Holdren: You should look at the scientific literature [interrupted] rather than the public comments …
Bucshon: Of all the climatologists whose careers depends on the climate changing to keep themselves publishing articles? Yes, I could read that, but I don't believe it.
Tides of Change
Another recent development in this debacle is that climate-change deniers have seized upon a study published by researchers on the role of the oceans as additional proof that our planet is regulating itself.
The paper, which was published in Science, was written by Xianyao Chen of the Ocean University of China and Ka-Kit Tung of the University of Washington. The scientists got a lot of publicity courtesy of Wall Street Journal columnist Matt Ridley, whose scientific errors are the stuff of legends.
In a column titled, "Whatever Happened to Global Warming?," he writes:
Last month two scientists wrote in Science that they had instead found the explanation [for the hiatus] 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.
Did Ridley read this paper? I only ask because the scientists wrote in their study that that the effects of the oceans siphoning off heat is expected to last a decade, adding that, "When the internal variability that is responsible for the current hiatus switches, as it inevitably will, another episode of accelerated global warming should ensue."
Jeffrey Sachs, the Director of the Earth Institute at Columbia University, published this lengthy critique of Ridley's column:
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.
[And] 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.
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. 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. 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.
If Ridley can't grasp when a research paper is arguing that human-caused climate change is happening, that could explain why he and other deniers continue to insist there is no scientific consensus on the issue.