SPACESHIP EARTH. Managing our planet
THERE'S a sure-fire way to find out what human activity is doing to our planet: We can wait and see what happens. But if we let the system perform the experiment - to use climatologist Stephen H. Schneider's metaphor - it may be too late to repair the environmental damage.Skip to next paragraph
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``We have become part of the Earth system and one of the forces for global change,'' according to NASA's Earth System Sciences Committee (ESSC). ``These changes seem irreversible,'' warns Francis P. Bretherton, ESSC chairman and Dr. Schneider's colleague at the National Center for Atmospheric Research (NCAR). He adds: ``Unless they are perceived and understood in a timely manner, all are likely to be stressful. We must start now to lay the foundation of knowledge and understanding for our successors to act upon.''
In short, humanity must prepare to actively manage the planet.
To do this, we need a way to foresee what effect human activity has on Earth's environment and to anticipate how changes in that activity would forestall dangerous results. Computer simulation - such as the climate modeling work of Schneider and his colleagues at NCAR - is the only way this can be done. The trick, Schneider says, is to use this computer guidance effectively in spite of its uncertainty.
HE explains: ``[There are] people in the policy business who are demanding that we give them answers. And they don't want the answers after the system performs the experiment. Of course, the truth is we can't give them answers before [then]. We can give them scenarios. And we can define the probabilities of those scenarios.'' He adds: ``I think the biggest problem in policy is people expect us to say `yes' or `no,' what's going to happen. ... One of the reasons we have policy difficulties ... is that people have the [wrong] idea that we're going to ultimately have exactly the answer. And I think that we're not. What we're going to do is find the ranges of possibilities and consequences.''
Schneider illustrates this with the problem of carbon dioxide (CO2) and climate. This heat-trapping gas slowly accumulates in the atmosphere as we burn fossil fuels. It slows the escape of heat to space, slightly raising Earth's average surface temperature. This is the so-called greenhouse effect.
As Schneider points out, there's nothing controversial about the greenhouse effect. It's one of the best established theories in planetary science.
`WHAT is controversial,'' he says, ``is whether the small [temperature] increment is going to make a large enough difference to be of social and environmental importance.'' This uncertainty - plus the fact that any significant effect is unlikely to come until well into the next century - leaves policymakers wondering what, if anything, they should do about CO2 emissions.
Schneider notes that computer-generated scenarios give no clear pictures of what might happen to regional water supplies as CO2 accumulates. ``Current betting is slight reductions in the US. But I have to warn that the current betting has only a 51 percent chance of being right, in my opinion. Two out of three models agreeing does not constitute proof, by any stretch, on hydrology. ... [But] models agreeing on temperature does [constitute proof] because, in fact, it's not two out of three but it's 22 out of 23.''
What the computer studies can do, Schneider explains, is show there's a reasonable chance of substantial climatic change. Then, he adds, ``[we] can re-ask the question and ask what are the vulnerabilities of the system. ... What biological systems are vulnerable to changes of what kind? And then ask the physical scientists if there's any probability to those changes.''
Given the uncertainties about CO2's climatic impact, Schneider says it's too soon to try to work out a world policy to curb use of fossil fuels. Among other things, use of these fuels is embedded in the global economy. Asking third-world countries, in particular, to drastically restrict the burning of coal and oil is to limit their economic development.
However, he adds, the simulations do suggest that some action be taken - action that is in the nature of insurance and that would be worth taking anyway.
FOR example, some computer-generated scenarios suggest there'll be longer growing seasons in high latitudes. Some agriculture could move up there if, say, American wheat lands dry out. So, Schneider notes, it would make sense to start developing the seeds for crops that can handle the variable weather of those latitudes.
In general, he says, there's a case to be made for more fuel conservation, especially in developed countries, to slow down CO2 accumulation. ``There's nothing new in that,'' he observes, `` ... you'd have less air pollution, less acid rain, less dependence on foreign supply.'' Also, he adds, ``You develop alternative crop strategies. You develop and test them and find out which ones can work better in wet or dry [conditions] and so forth. And my gosh, that's actually useful in dealing with regular climate variability.''