SAGE

Convincing the Climate-Change Skeptic: Nitty-gritty

By Daniel Sinnett

Q: What are the five most difficult questions asked by smart climate-change skeptics at cocktail parties? And what are the best responses?

Asked by Gil Masters, PhD '66, Palo Alto, Calif.

You're well into your cocktail hour and have debunked two of the skeptic's questions. He remains unconvinced, though, so order yourself a virgin drink and keep your wits about you. These questions are a little more difficult and require more explanation than those found in the Essential Answer.

If CO₂ really causes global warming, why does CO₂ rise 800 years after temperature rises in the ice core record?

CO₂ does indeed lag behind temperature in the ice core record. It is also true that factors other than CO₂ contribute to climate change. The temperature variations in the ice core correlate with changes in Earth's orbit and orientation, termed Milankovitch cycles. These orbital cycles change how much solar energy reaches the Earth, causing the observed warming and cooling trends. At the start of a warming cycle, Earth's atmosphere begins to warm. This is recorded first in ice cores. Water takes longer to heat up than air, but when it does CO₂ begins to escape into the atmosphere, much like warm Coca-Cola loses its fizz faster than cold. The rise in CO₂ is now recorded in the ice cores following the lag. Since most warming periods in the ice record last 5,000 years, the CO₂ contributes to the remaining 4,200-year rise in temperature.

It is also telling that the total temperature rise cannot be accounted for by changes in Earth's orbit alone. The total temperature rise observed in the ice cores requires extra CO₂. Further, the CO₂ lag is seen in the ice core record, but the historical record tells a different story. The rise in anthropogenic CO₂ emission clearly precedes the temperature rise. In fact, climate models actually indicate that the Earth would be cooling were it not for the CO₂ we're pumping into the atmosphere.

Didn't that MIT climatologist publish a paper showing low climate sensitivity, so we don't have to worry about CO₂?

Papers published in peer-reviewed scientific literature deserve due consideration, and papers appearing to dispute the consensus are bound to be published from time to time, despite accusations of suppression of dissent. (Another favorite—and un-substantiated—trope of deniers.) If your cocktail hour adversary cites a newly published paper whose details are over your head, do not fret: instead, pull out your smart phone and check RealClimate. If it's a major paper, they'll have covered it. The paper related to this question was published by two MIT researchers, Richard Lindzen and Yong-Sang Choi, in 2009. The authors (henceforth LC09) investigated how sea surface temperature (SST) affects the amount of energy radiated back into space over the tropics. LC09 claim that the observed radiation shows a low sensitivity of climate to atmospheric CO₂, or, more simply, that even a large increase in CO₂ would cause only a minor change in temperature. The paper led to some self-analysis by climate scientists: If true, LC09 would overturn one of the major tenets of climate change science. A paper's true worth, however, is determined by how the science holds up under the microscope. About a year later, scientists at the National Center for Atmospheric Research, University of Colorado and NASA published a paper (Trenberth et al, 2010, henceforth TFOW) that rebutted LC09.

Among the most grievous of errors found by TFOW is what appears to be data picking to conform to expectations. When LC09 ran their analyses, they looked at time periods over which SST changed (closed circles in the figure). LC09 did not choose periods that seem intuitive, namely times between extremes in SST. When TFOW made the more intuitive choice (open circles in figure) they found LC09's conclusions of low climate sensitivity to be false. This begs the question: did they choose data and analysis methods to support an already formed conclusion? Further, LC09 focused on the tropics only and ignored complications that arise from the connected nature of global climate systems. Hurricane Earl, born of the tropics, was very nearly an uninvited guest at my New Hampshire wedding last summer, and he would have ruined the pre-reception cocktail hour. Lastly, LC09 makes a variety of errors in their modeling and calculations of the climate system, leading TFOW to state that "the approach taken by LC09 is flawed, and its results are seriously in error." These are strong words for an objective research article (for a more in-depth analysis of the paper, see Realclimate's post on the matter). LC09's publication illustrates that peer-review is not a perfect filter. TFOW's analysis is also yet another example (e.g. the South Korean stem cell scandal) that bad science will be found out. If anything, papers like LC09 and TFOW should give you more confidence in the robustness of climate science.

Courtesy Kevin Trenberth

Okay, okay, so climate change is real. But aren't there benefits, and wouldn't mitigation cause a second Great Depression?

Hopefully you've argued persuasively, and your opponent's concession isn't just the cocktails speaking. Answering this question might be a little tricky, so for some help I sought out, and found, a worthy adversary who does not think climate change will cause major problems. As it turned out, my adversary, an economist named Dr. Thomas Moore, at Stanford's Hoover Institution, was less "adversary" than "amiable person with opposing views." He would be an excellent cocktail companion. Since Dr. Moore does not dispute the science of climate change, the interview was much friendlier than some of my other debates with plain old deniers. Since I have no background in economics, Dr. Moore's arguments were initially very persuasive. During our interview, Dr. Moore made three main points: 1) global warming has some benefits, 2) rich countries can deal with any ill effects, and 3) mitigation will cause great economic harm. We discussed a variety of subjects, a few of which are outlined below.

In his book, Climate of Fear, Dr. Moore notes that warm periods correlate well with population and cultural growth throughout Europe and parts of Asia. Cold periods in contrast are highlighted by famine, disease, wars, and large population declines. While these points may be true, I feel they miss a key fact: climate change and resource exhaustion can cause significant societal stress, a subject highlighted by Jared Diamond. Other benefits of a warmer world include a longer growing season, especially in the northern latitudes, due to warmth and a richer CO₂ environment. Since I want to focus more on other elements of the interview, I suggest looking at the Skeptical Science blog, which I mentioned in the Essential Answer, for more pros and cons of climate change.

The biggest negative that Dr. Moore foresees is sea level rise, something he says developed countries can manage fairly cheaply. The Netherlands have been dealing with unruly seas for centuries, and rich countries can draw on their expertise to deal with rising seas relatively easily. Further he claims, dealing with sea level rise will be cheaper than mitigation methods. The Maldive islands will have a real problem if sea level rise gets to three feet, "on the other hand," said Dr. Moore, "there [are] only 750,000 [of them], and we could move them all. . . that'd be the cheapest thing to do." This may be true for the Maldives, but I see significant problems to applying this solution to the 100 million people estimated to live within three feet of sea level. Even if portions of this 100 million living in developed countries can be protected, such a large migration of people would pose significant problems to countries accepting these climate change refugees.

Rich countries will also be able to deal with changes in precipitation around the world. Many water management problems—particularly in the U.S.—could be effectively dealt with if water was sold at a market price. For example, farmers currently grow cotton and rice in California even though "it doesn't make any sense to do it in a desert climate, but because the water is dirt cheap. . . they can grow cotton and grow rice." For drinking water, Dr. Moore points to desalinization. Israel, the UAE and some island nations use desalinization on a large scale. However, desalinization will not work for landlocked countries or those at high altitude, and these areas will be most affected by water shortages due to climate change.

The reason why Dr. Moore believes changing precipitation patterns won't be a large issue is that "one of the things economists understand, is people adjust. . . scientists don't take that into account; that people adjust." I agree people adjust to change, but the cost of adjusting to the climate change may be astronomical. The adjustment phase will be fraught with wars for resources, droughts, famines and large numbers of displaced peoples. If events in the Sudan are any indication, dealing with these issues will not come easily or without political cost.

Dr. Moore's nuanced views on climate change mitigation made my interview refreshing. While it was clear he felt that cutting greenhouse gasses by 80 percent "would make the great depression look like a period of great prosperity," he has thought about mitigation strategies. Dr. Moore feels very strongly that "if you want to do something about it. . . cap and trade isn't the way to go," as it's "a recipe for corruption." Instead, Dr. Moore prefers a global carbon tax, calling it "clean; efficient." His plan "would be to have [the taxes] collected by a new world body, set up to take the money and spend it on helping the poor nations of the world. . . get good medical care, get good sanitary systems, and get rid of diseases like malaria." In regards to biofuels and "that ethanol crap," Dr. Moore states that it uses too much land, raises the cost of food, and puts a larger burden on the world's poor.

I connected with Dr. Moore's feelings here. Some of the largest challenges developing countries will face from climate change are due to poverty. Diseases such as cholera or malaria are easily dealt with in the developed world. Instead of spending money on mitigation to stave off future deaths, Dr. Moore would "spend it on providing clean water," and that "we could save lives today, rather than hypothetical lives a hundred years from now - I'd rather spend the money now and save these lives today." I agree with Dr. Moore's sentiments, but I feel like they're more of a pipe dream. The majority of Americans already believe we spend too much on foreign aid, and one of the country's most-watched conservative commentators, Glenn Beck, wants an isolationist United States.

I hope your cocktail companions are more like Dr. Moore, and less like my Facebook frenemy. Science is an evolving field, so the best way to keep up is to watch the published papers. The best way to do that is through RealClimate and Skeptical Science. Skeptical Science contains basic and moderately in-depth descriptions of climate science. RealClimate's articles are often more technical, but contain a wealth of information. Never be afraid to simply say, "I don't know, can I get back to you," and then do so. And lastly, whenever it's clear that neither person will get anywhere in the discussion, don't hesitate to say, "ah forget it, want another drink?"

DANIEL SINNETT, MS '10, is a PhD student in geophysics.