Climate change top concern for 21st century

Steven Schultz

Princeton NJ -- The subject of climate change returned to the news in recent weeks with President Bush's proposal for curbing greenhouse gas emissions. Michael Oppenheimer, Princeton's Albert Milbank Professor of Geosciences and International Affairs, recently spoke with the Weekly Bulletin about the mix of science and policy that underlies the climate change issue.

Oppenheimer joined Princeton this semester after 20 years at Environmental Defense, a private not-for-profit research and advocacy group. For the last five years, he was the organization's chief scientist and manager of its global/regional air program.


Michael Oppenheimer

He is the co-author of "Dead Heat: The Race Against the Greenhouse Effect," published by Basic Books in 1990. Oppenheimer is currently teaching a graduate course, "Earth's Atmosphere: Theory and Practice."

How concerned should we be about climate change?

Climate change is the top environmental problem of the 21st century. If nothing is done to restrain the emissions that are causing the buildup of greenhouse gases in the atmosphere, then our children and grandchildren are likely to experience a global warming unprecedented in the history of civilization.

And Earth is already starting to change. The climate is now significantly different than it was 100 years ago, even 30 years ago. Although one can't assign the cause of the weather in any one season to the overall global trend, what we've seen this winter is consistent with the sort of changes that are going to occur more and more frequently.

Signs of the trend include the observations that lakes and streams ice over later in the fall and melt earlier in the spring. Glaciers are in retreat worldwide. Springtime is coming significantly earlier. So the trend of global warming, which has been building since the start of industrialization, is starting to have consequences that are perhaps not yet terribly painful, but are certainly becoming noticeable to the average person.

Some people might say, "Fine. So it's as though I'm moving closer to Florida. What's wrong with that?"

Greenhouse gas emissions are changing the entire Earth system at once. We have only one world, and we're doing a massive experiment on it. And our tools for determining the outcomes are quite limited. It's the height of optimism to think that these changes can continue without substantial risk that they will have disruptive consequences.

Computer simulations and our knowledge of past climates suggest that greenhouse gases may be undermining the relative climate stability that has characterized Earth as a whole for the past 10 millennia.

Currently we have an interesting analogue here in New Jersey of what we may see more of in the future: water systems having difficulty, partly because of absence of winter snow pack. Summer rainfall is less useful to water supplies than snowfall because it largely evaporates and doesn't wind up in reservoirs. One of the predictions we can make with relative confidence is that warming will diminish the winter snow pack because the snow season will likely become even shorter.

Warming also will affect agricultural productivity. The U.S. could wind up with a net gain, but countries at low latitudes in semi-arid regions -- developing countries, where malnutrition is already common, such as parts of India, Mexico and Sub-Saharan Africa -- are projected to have significant decreases in grain production. This is bound to aggravate the conditions that cause malnutrition and episodic starvation.

Overall, if emissions do not abate and the world warms at the low end of projections -- about 3 degrees Fahrenheit over this century-- we would move into a world where many natural ecosystems, like coral reefs, could be largely squeezed out of existence. Most societies could adapt, but some, especially coastal regions like Bangladesh, will have trouble even with a modest warming. At the high end -- about 10.5 degrees Fahrenheit -- the changes would essentially remake the natural world and could prove highly disruptive to every country. The potential for disaster is there.

President Bush's recent proposal seeks to control greenhouse gas emissions through voluntary guidelines that become less restrictive in a weak economy. There has been criticism that the plan does not go beyond existing laws and trends. Is that so?

The U.S. has had a trend of improvement in energy efficiency in the 1990s, and also over the longer term. The Bush administration is essentially saying, "We think the trend is going to slow down a little, and we're going to speed it up a little to get it back up to the trend we had anyway." By 2012, the end date of the president's proposal, no one will be able to tell whether any of the improvements happened because a bunch of public money was spent encouraging energy efficiency, or if efficiency improvements occurred just as they would have anyway. So the program could be charitably characterized as unambitious. To a cynic, it looks like just a way to delay action.

What about overall philosophy that a strong economy is a necessary first step in implementing environmental measures?

The U.S. has the technological prowess to substantially diminish its dependence on fossil fuels, which are the main cause of the greenhouse problem. So we don't have to worry that our larger economy is at stake if we move to solve this problem. And after all, the estimated costs of implementing the Kyoto protocol (a proposed international framework for reducing greenhouse gas emissions) or similar efforts are very modest compared to projected economic growth over the period. And the associated benefits in terms of reduction of air pollution as well as other environmental impacts would be immense.

As a scientist, is there one technical point that you would like the public and politicians to better understand?

Carbon dioxide, the main greenhouse gas of human origin, has a very long residence time in the atmosphere. Some human-made carbon dioxide will be removed by natural processes within decades, some of it within centuries and some of it will still be there for millennia. Emissions today entail a very long commitment to warming. We can plant a lot of trees, or implement other geo-engineering measures that will take some of it out, but the reality is the best way to minimize global warming is to keep the gases out of the atmosphere in the first place.

The buildup of carbon dioxide in the atmosphere is like the water level in a bathtub with the faucets way open and the drain nearly clogged. In this case the faucets are cars, power plants, factories. To stop the tub from filling, you would have to turn the faucets way down. If you wanted to stop this experiment today, you would have to turn down emissions by a very large amount -- more than half of current levels -- to stop the warming in its tracks. In practice, you can't do it overnight, but the quicker we begin to do so, the easier the task will be.

What would you propose to do as a first step?

If the U.S. isn't going to adopt the Kyoto protocol, it should at least implement a serious program that is consistent with the goals of Kyoto, and then work with the international community to make the adjustments in the protocol that would address the concerns of the U.S. No one has argued that the protocol is perfect or the last word. It is the first step in a long process.


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