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The Economist's Climate Deep Dive off the Shallow End

Dan Lashof

Posted April 12, 2013 in Solving Global Warming

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The Economist is a well-regarded magazine. Its writers aren’t loony science deniers, like those on the Wall Street Journal’s editorial page, or the broadcasters on Fox News. Generally speaking, their climate coverage wins high marks.

But an article the magazine published recently—“A Sensitive Matter”—has misled or at least grabbed the attention of a lot of people; I have been asked about it by several of my NRDC colleagues, leaders of other environmental organizations, and (through Facebook) a high school classmate, turned investment banker. It raises reasonable-sounding questions about how quickly our world is actually warming and how accurate models are that predict climate changes going forward. Is global warming actually accelerating as forecast? Or, are things slowing down, at least a little? And what does this mean for policy?

It really would be nice if there were solid reasons to think, as the Economist article suggests, that the pace of climate change will be at the low end of the range of mainstream forecasts. That would give us more time to cut carbon pollution, reverse deforestation, plug methane leaks, and reduce the other major drivers of climate change.

No such luck.

As it turns out, the article is a more sophisticated, but no more valid, version of the long-standing climate denier claim that global warming has stopped since [1970, 1977, 1988, 1998]. The Skeptical Science website provides an excellent illustration, reproduced here, of what happens if you cherry pick the starting point of a trend analysis of data that includes significant natural variability, as our climate does. The Economist doesn’t go this far, but it does engage in equally dubious cherry picking of the scientific literature, including some genuine scientific uncertainties, to reach a false conclusion, as Dana Nuccitelli and Michael Mann point out in an excellent response posted yesterday.  

At issue, in the article anyway, is a concept called “climate sensitivity”—how much the climate reacts to changes in greenhouse gas levels. Will a doubling of the carbon dioxide in the earth’s atmosphere, from preindustrial levels to 560 parts per million, result in a temperature increase of “just” 2 degrees Celsius or is a full 4.5 degrees or more in the offing? No one is exactly sure. The best estimate from scientists, combining multiple lines of research, is about 3 degrees, the Economist story notwithstanding.

So how do we explain the apparent lack of increase in the earth’s surface temperatures over the last 15 years? Over this period the amount of heat-trapping pollution in our atmosphere has continued to rise: Carbon dioxide levels have now reached 395 parts per million and their climbing fast.  If carbon dioxide is trapping as much heat as we thought, where has it gone off to?

As it turns out, the answer is pretty deep. Deep in the ocean, that is.

About 90 percent of the excess heat trapped by increases in greenhouse gases ends up in the ocean. Our atmosphere is very thin, after all, and it just doesn’t have that much capacity to store heat. The ocean’s heat capacity, by contrast, is vast. Surface air temperatures should be thought of as responding to the temperature of the ocean, rather than the other way around. The ocean also has distinct layers, which mix slowly. Much of the natural variability of our climate from year to year comes from heat sloshing around among different parts of the ocean.

The starting point for the claimed global warming hiatus should be the tip off.  1998 was a very hot year—one of the three hottest on record, and well above the trend line at that time. That year, an El Niño—a warm Pacific current that can cause extreme climate variations—moved a lot of heat from the ocean to the surface. And since then, that heat has been seeping back. Still it was difficult to account for all the additional heat because it has accumulated deep in the sea, at depths well below 700 meters, where there have been few measurements until recently. This was documented in an important paper (subscription required; good summary here) published last month by Balmaseda, Trenberth, and Källén, and explained in this handy graph.

The results shouldn’t surprise us. In 2011, researchers at the National Center for Atmospheric Research showed in repeated simulations of climate change over the last century that frequently there are pauses in surface warming as heat dives into the deeper parts of the ocean, similar to what Balmaseda et. al. have observed. 

In climate science, there are some legitimate disagreements about which models best predict climate change. But let’s be clear: We can’t afford to assume that we will be lucky. Anything above 2 degrees is the global warming red zone, beyond which we tread at our rapidly escalating peril.

It’s magical thinking to believe that because the rise in surface temperatures may have paused for a few years that we’ve gotten a free pass or a breather on climate change. That we need not push hard for cuts in carbon emissions from fossil-fuel-fired power plants. That we need not scale up renewable energy and energy efficiency at a rapid clip.

Already, the earth’s temperature is more than 1 degree Celsius higher than it was 70 years ago. The Economist article acknowledges that, even as it creates confusion and unjustified hope that we dodged a bullet.

The earth’s missing heat can be found deep in the ocean. Let’s not bet the planet that it won’t come back to haunt us.

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Andy RevkinApr 12 2013 09:38 AM

Dan, I'm afraid you (and perhaps The Economist) are conflating two separate and important questions in climate science.

Clarifying how much heat is moving into the deep ocean can help refine understanding of how much a big rise in concentrations of greenhouse gases can warm the climate, but is is not a forcing factor in itself (like greenhouse gases, different clouds and particles, etc.).

The significance of the length of the current "pause" (Susan Solomon and Jim Hansen acknowledge its reality) is that it gets harder to explain if the climate-system sensitivity is at the high end of the longstanding range. Another couple of years would -- even with what's known about ocean heat -- essentially trim off the high end. As you note, the mid-range warming comes with lots of risks, as well, so none of this produces a "false alarm" conclusion.

The link here leads to some of my Dot Earth coverage on these questions.

Environmental EngineerApr 12 2013 10:11 AM

I was going to read your blog, but had to stop at "loony science deniers" in the second sentence. Yes, there are some irrational views expressed on the climate change topic. But those irrational views are on both sides. Neither represent the vast center ground where actual facts, figures, theories, data, and solution methods are to be found. You are simply adding fuel to the fire with this type of inflammatory rhetoric. Polarization and name-calling does not lead to intelligent, meaningful discussion.

LHApr 12 2013 10:49 AM

Climate sensitivity also becomes far less relevant as we continue a business-as-usual approach that threatens to triple or even quadruple CO2 levels by the end of the century.

Even if sensitivity is lower than the current consesus, we're still gonna blow past that temperature rise through the absolute level of CO2 we emit.

Kevin KerrApr 12 2013 04:21 PM

The transfer of heat to deep oceanic water is much more of a risk than people realise. Large quantities of methane clathrates exist at depth and oceanic warming could release this greenhouse gas producing a tipping point.
Instead of arguing about the rate of Global warming politicians should be thinking of how to cope with the changes it will produce.

James Singmaster, III, Ph.D.Apr 16 2013 01:23 AM

'Everything's haywire with CC/GW calculations missing the basic point of what we know is causing it and then saying what can we do to stop it. Undoubtedly the world is warming due both to CO2 levels rising and heat being released from trapped energy in fossil fuels (CO2 & Heat) and nuclear materials(Heat only). Heat energy is the amount of motion that molecules have, and they are trapped on Earth by gravity. So heat energy once released can not escape Earth and will accumulate.
Can we reverse CC/GW?????? Yes if we MAKE THE SUN OUR SOLE ENERGY SOURCE. Then we would not need to be get oil and coal out of the ground and not need to be trying to get energy from the atom. Briefly THE HYDROGEN AGE is here with H2 being gotten by splitting water using sunlight and a catalyst. We also can be using solar collecting mirrors to distill ocean, brackish, even sewage water to get fresh that is needed in many parts of the world with drought problems getting worse.
We also need to reestablish the CCC program of Roosevelt to plant new trees while getting dead and dying trees harvested to be sent to pyrolysis plants to reform charcoal reversing what happens in burning and to get an expelled mix much likr light oil from oilwells. Making charcoal in this manner provides, if buried, a way to reverse. CC/GW. We also can pyrolyze all our biowaste messes including separated sewage solids to get the fuel mix and charcoal, but charcoal in this case will have some plant nutrients and so can serve as soil amendment.
Our present mishandling of biowastes to be dumped and get biodegraded reemitting CO2 and trapped energy is a multitrillion dollar/year loss for the economy of the world. AND escapes of germs, toxics and drugs from mishandled biowastes may be what wastes the futures of our children.
To illustrate how biowastes are getting out of hand, I point to EPA's putting over 2 years ago limits on several synthetic female hormones showing up in drinking water. WHAT DOES EPA DO IF THOSE LIMITS GET EXCEEDED????????????
They are getting there because sewage water is not being treated correctly. I am surprised that NRDC has not raised a stink about this because it has worried about every other thing in drinking water. Sewage water is presently mishandled to have much biodegrading happening with aeration so that unneeded CO2 and heat loss occurs.
If we take steps to get control CC/GW, we can recover billions of $$$$$$$$ presently being wasted on mishandling of biowastes where present operations costing plenty end up worsening CC/GW. Dr. J. Singmaster, Fremont, CA

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