To Open The Sky
The Front Pages of Christopher P. Winter
Debunking Denialist Arguments Against AGW Science
Scientists have been documenting the gradual warming of Earth's climate for decades — compiling temperature records for thousands of ground locations worldwide; scanning the planet with satellite-borne sensors; monitoring the concentration of carbon dioxide and other components of the atmosphere.
The What Effect?
The basics of the Greenhouse Effect are seldom explained. I thought a brief review would be helpful.
Heat is transferred in three ways: Conduction (like touching a hot stove), convection (air currents), and radiation (like a heat lamp). Across empty space, the only one that works is radiation — electromagnetic energy: light.
The Sun radiates in a wide spectrum. It heats the Earth mostly with visible and infrared light. (Infrared wavelengths are slightly longer than visible.) The atmosphere blocks or passes certain wavelengths of light, depending on what gases it contains. Some of these gases pass visible light and block infrared.
Sunlight heats the surface during the day. But at night, the heat that radiates back into space is infrared light. Water vapor traps infrared. So does CO2. So does methane. (So do a host of others, but they are too rare to matter much.) This means that some of the infrared light is blocked by these gases; some heat cannot escape into space. Add more of these gases, and you trap more heat.
These gases are the reason life exists on Earth. Without them it would be 20° or 30° colder. We call this the Greenhouse Effect, even though an actual greenhouse works differently. (It holds heat by preventing convection.) Thus, the gases that cause it are greenhouse gases.
Despite this extensive documentation of the scientific basis for global warming, the reality of the phenomenon has been vigorously debated for twenty years now. The documentation is very accessible: Articles debunking the FACs (frequently advanced counterarguments) can be found on the Web sites of The Climate Institute, Britain's Royal Society, and many others. (The list of references below is a good start.) These sources explain the shortcomings of those counterarguments in detail. To borrow a phrase, The Truth Is Out There. So why does the world need yet another site debunking the denial of global warming?
Because, for a segment of the population, that truth is not sinking in. Because, for whatever reason, that vocal minority still advances their faulty arguments on the Web, in books and newspaper articles, and in television "documentaries". Because the illogical, self-contradictory nature of those arguments is not being widely recognized by the public or by the mainstream media. Because some people, even some scientists, are still basing their denials on mere assertion. And because I think that the more places people can find clear explanations of the problem, the better.
In this discussion, I go for clarity over scientific terminology. True, much scientific work was required to piece together the picture of climate we have today, and scientific terminology is required for full understanding. But the broad outlines of the picture are clear, and you don't need a Ph.D. to understand them. They give us cause for concern — not for alarm, not for urgent action. Yet how much closer to the time when urgent action might be required have twenty years of needless delay brought us? We cannot know precisely, just as we cannot know precisely how much sea level will rise by the end of the century. But we know it will rise, and is likely to rise enough to affect many low-lying facilities.
That is why we must begin to act. We don't need a crash program. We do need a program. Twenty years of denial have not changed the facts: Global warming is real. Twenty years of stubborn resistance to government action have not led us to a time when combatting climate change has been shown to be unnecessary, either because it stopped happening on its own, or because voluntary efforts gave us solutions.
The barriers to understanding must be dismantled. In hopes of aiding their dismantling, I debunk here the arguments commonly used against global warming (more specifically, against Anthropogenic Global Warming, or AGW — the idea that the warming of the globe, which few deny, is caused by human activities.) These are not the only objections raised, but they are the most commonly heard.
Click the large number in each table below to jump to references on its topic.
The Bottom Line on Climate Science
Climate science is complicated. There are lots of factors involved, and many details of how these factors interact are still unclear. No scientist can say exactly how Earth's climate will behave in fifty or one hundred years. But the broad outlines of the picture are clear: The world is getting warmer, and the best evidence shows the cause to be rising CO2 levels due to human actions. This evidence comes, not from abstruse theories or computer models, but from over a century of direct measurements of temperature at many locations, fifty years of CO2 measurements, over thirty years' monitoring of the Sun's brightness by satellites, and decades of worldwide research on proxy data to give us a long-term baseline for comparison.
The bottom line is that there is no longer any rational basis for disputing the big picture. It is true that new discoveries might reveal a different cause for the current rise in temperature. But those who say this discovery has already been made are obliged to support their claim with solid evidence. So far, none of their evidence has held up to careful scrutiny.
The bottom line is that the unscientific nature of Denialist arguments about climate science and the self-contradictory nature of their case make it clear that their goal is to confuse rather than clarify the public's understanding of climate science.
References on Specific Topics
"In the 20th century, for the increase in the CO2 concentration to be entirely due to an increase in temperature that should have been around 5°C. That has not occurred and leads to the inevitable conclusion that the recent increases in CO2 concentrations are because of the burning of fossil fuels. The answer comes from a study of the temperature dependence of the Henry's law coefficient for the solubility of CO2 in seawater. This has been very carefully quantified by the Brookhaven National Lab and can be relied upon. That the 20th century saw an increase of temperature of 0.6 +/- 0.2 °C implies that an increase in CO2 atmospheric concentration should have resulted of around 10 +/- 3 ppmv. That much more than this increase occurred seems to lead to the conclusion that there is another source. All the evidence we have in the literature points towards the burning of fossil fuels. So, about 10 ppmv from a slight temperature increase and the rest is down to us."