By Donella Meadows
–September 28, 1989–
“High Cost of Greenhouse Hysteria” reads one recent headline. Another says “Greenhouse Effect Looks Like Just a Lot of Hot Air.” And a third: “Environmentalists, Not Pollution, are the Real Threat.”
The backlash has appeared. Once the greenhouse effect was popularized, it was sure to become politicized.
Folks who are unhappy with the state of the world anyway are using one hot summer to call for major social reforms. The comfortable folks who always oppose change would rather not believe in global warming at all. They will probably go on denying it until they see palm trees grow in New York and rising seas lap the White House steps.
One side likes to quote scientists like Dr. Paul Ehrlich of Stanford, who can always be counted on to be alarming: “We are going to see massive extinction…. We could expect to lose all of Florida, Washington D.C., and the Los Angeles basin…. We’ll be in rising waters with no ark in sight.”
The other side searches out Dr. Reid Bryson of the University of Wisconsin, one of the few unconcerned climatologists: “The … statements that the greenhouse warming is here already and that the globe will be four degrees Centigrade warmer in 50 years cannot be accepted.”
The earth, of course, does not lean right or left. It has no preference for stability or change in human institutions, nor does it summon authority by selective quotation from biased sources. It operates by inflexible laws, which human beings, when they’re not in knee-jerk political mode, can understand — partially anyway.
Fortunately, as greenhouse politics becomes more muddled, greenhouse science is becoming more clear. I’ve been watching the literature for twenty years, and I’ve just come back from one of the innumerable conferences on the subject. Though there will always be maverick scientists for the politicians to quote, in fact there is strong consensus on this subject. I’d guess that 99 percent of scientists would agree with the following conclusions.
1. The greenhouse effect is a certainty. One of the first Nobel Prize winners, the Swedish chemist Svante Arrhenius, explained 100 years ago how greenhouse gases trap the sun’s energy and warm the earth. He warned that one of those gases — carbon dioxide — is released when we burn oil, gas, or coal, and he calculated how much the earth would warm if we burned enough fuel to double the carbon dioxide in the atmosphere.
A hundred years later his reasoning is accepted, and his calculations are still close to the mark. The main thing that has changed since Arrhenius’s time is that humans now create gases he never heard of — like cholorofluorocarbons (CFCs) — which are more powerful and long-lasting heat traps than carbon dioxide.
2. Greenhouse gases in the atmosphere are increasing faster and faster. They have been measured directly for 30 years, and indirectly (from air bubbles buried in polar ice) for 200 years. Different gases are increasing at different rates, but all of them in upward-rising curves. More are added to the atmosphere each year than the year before.
If these atmospheric changes go on at their current rates, the equivalent of Arrhenius’s carbon dioxide doubling will be reached about the year 2030 — when a child born this year is 41 years old. That may not happen, because we may stop it. It also could continue well beyond a mere doubling, if we do nothing at all.
3. We are the cause of the increase. Primarily by fuel burning, air pollution, the manufacture of CFCs, and deforestation. These activities are also increasing faster and faster, with the growth of the human population and economy. (There is a global agreement to reduce CFC production, which hasn’t yet gone into effect.)
4. There is a long time lag between greenhouse gas increase and measurable climate change. That’s partly because the oceans and ice sheets act as a delay or drag. It’s partly because climate is a lagged indicator — climate is the average of weather over one or two decades. Weather is variable, noisy, shifting. You have to keep track of it for years, before you can be sure the climate has changed.
Therefore, if we wait to prove the greenhouse effect by measuring climate change, we will confirm it several decades too late to do anything about it. We should take our cues from the leading indicators — the atmospheric concentrations of greenhouse gases. Their message is already undeniable.
5. The exact nature of a greenhouse climate change is highly uncertain. Anyone who tells you that Russia will be better off with a global warming, or that the Midwest will dry up, or that there will be more rain in the Sahara, is going well beyond what scientists know. Just which places on the planet will be hotter, colder, wetter, or drier is still a matter of controversy. (The scoffers like to “disprove” the greenhouse effect by showing that a single place — like the continental USA — has cooled lately. Those data, derived from just a small percentage of the earth’s surface, are irrelevant to the global picture.)
There are two other messages, of particular importance to politicians, that are emerging strongly from the scientific meetings.
6. A climate change as rapid as the greenhouse change is likely to be will be disastrous for the earth’s ecosystems and for the human economy. We are more dependent than we realize on the seacoasts, rainfalls, rivers, and seasons occurring just the way they occur now.
7. Only a small amount of global warming is now inevitable. The greenhouse effect is talked about too much as a matter of destiny and too little as a matter of choice.
Those points are so crucial that I’ll come back to them next week.
Copyright Sustainability Institute 1989