In this post, I present a layman's primer on global warming. But before we begin, I'm so excited and full of thanks for the fact that I have received more than 2 x 350 = 700 emails of support for my coming visit to Congressman's Nadler (click here to help me reach my goal of 3 x 350 = 1050). Thank you to the many to bloggers who have spread the call, like May at 350.org, but more especially, those who are outside the green space like Ikea Hacker and Wise Bread (I plan to mention the rest of you generous bloggers in the coming days).
During my visit to the Congressman, I plan to ask him to sponsor a non-binding resolution in the House of Representatives calling for a climate change mitigation policy based not on what seems politically possible but on what is scientific necessary (go here for details and to read how to send an email of support). I will ask him to support the climate platforms of 1sky and 350 and to take the plea to House Speaker Nancy Pelosi.
But one thing I've realized is that many of us don't quite understand the complicated question of how carbon dioxide and other greenhouse gases warm the planet in the first place and why the 350 goal is so important. For that reason, I've included this draft of an explanation that I'm working on for my book. I'm sure it's imperfect, and I'd love for people who know more than me to weigh in, but I think it's a good first stab at a layman's explanation.
For starters, greenhouse gases, for all the bad press they’ve been getting lately, keep us alive. Well, not so much keep us alive as allow us to be born in the first place. Because the greenhouse effect, as it’s called, is what keeps the earth at livable temperatures. The moon, for example, which has no atmosphere and therefore no greenhouse effect, bakes away at inhuman temperatures during the day and becomes an icicle's icicle at night. On earth, greenhouse gases in the atmosphere help keep us cozy.
“We’d all be dead if it weren’t for the greenhouse effect,” the climate change naysayers like to say, “so what are you worried about?” But the problem is not the greenhouse effect, per se. The problem is that the greenhouse effect is getting, as the climate scientists say, “enhanced.”
As it goes, certain naturally occurring gases in the earth’s atmosphere have little or no effect when it comes to warming up the planet—like oxygen and nitrogen. The sun’s rays can pass through these gases, bounce off the earth’s surface, and be reflected unencumbered back out into space. Certain other natural gases in the atmosphere—like water vapor, carbon dioxide, methane, nitrous oxide and high-altitude ozone—have the effect of absorbing and trapping heat from the sun and warming the place up—the greenhouse effect.
It turns out, though, that since the beginning of the industrial revolution, human activities—especially burning fossil fuels, cutting down forests and raising cattle—have begun increasing levels of those naturally occurring greenhouse gases. We’ve also added to the atmosphere a cocktail of other greenhouse gases that would not normally be there—like low-altitude ozone, substances known as halocarbons and a bunch of others.
The more we fill our atmosphere with these gases, the more we “enhance” the greenhouse effect, the more of the sun’s radiation gets absorbed and trapped, the warmer the Earth’s surface becomes. Think of throwing on a heavier blanket or putting double-glazing on the greenhouse or putting insulation on a building. Except that in the case of a planet warming, things get a lot more complicated and difficult to understand and predict.
For one thing, there is a tipping point, the level of greenhouse gas beyond which the associated temperature rise will cause damage—such as massive species extinction and the complete melting of polar ice—that cannot be undone. For another, as we continue to produce greenhouse gasses, we’ll reach this tipping point much faster than simple analysis might predict, because it turns out that the more we warm the planet, the more the planet warms itself. The scientists call this “positive feedback.” The rest of us might call it a frighteningly vicious cycle that goes, for example, something like this:
Warm the planet by adding greenhouse gases, and next thing you know, you get water evaporating from the oceans and entering the atmosphere as water vapor—the strongest of the naturally occurring greenhouse gases—which warms the planet more. Warm the planet enough to melt some sea ice and what used to be a highly-reflective white surface that sent sunshine back into space is now the dark blue surface of ocean water which absorbs it. Again, more warming.
The bad news is that the list of positive feedback effects goes on and is more extensive and complicated than anyone understands. Suffice to say, warming causes a domino effect that begets a lot more warming. In fact, in a study of the earth’s geological history, the United States Government’s most senior climate scientist, James Hansen, discovered that feedback effects increase the warming potential of carbon dioxide, the most important greenhouse gas, by a factor of three.
To put it another way, theoretically, when the warming contributions of feedback effects are left out, a doubling of the carbon dioxide in the earth’s atmosphere from pre-industrial levels would cause a temperature rise of 2° C (3.6° F). But in real life, in the actual recorded geologic history of our planet, thanks to the contributions of the positive feedback effects, a doubling of the carbon dioxide in the atmosphere has caused temperature to actually rise by 6° C (10.8° F).
Which brings me back to this question of the tipping point. Climate scientist across the globe agree that there is atmospheric concentration of carbon dioxide beyond which, if it stays at that level too long, the temperature will rise too much and the planet will irreversibly change.
According to Hansen’s analysis of climate history, that level is 350 parts per million (ppm) by weight. In other words, for every one million pounds of atmospheric gas, no more than 350 may be composed of carbon dioxide. This level must be achieved, Hansen believes, if, in his words, “humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted.”
And the problem is, we’re already at 387 ppm and it’s rising by 2 ppm a year.