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    Dr. Mario Molina

    (Nobel Laureate in Chemistry, 1995, Professor at Massachusetts Institute of Technology, Member of the President's Committee of Advisors on Science and Technology)

    Mario Molina was awarded the Nobel Prize along with Sherwood Rowland for research on the thinning of the ozone layer. Dr. Molina and his colleagues demonstrated experimentally how ozone-destroying chlorine functions in the atmosphere. He is currently the Lee and Geraldine Martin Professor of Environmental Science at Massachusetts Institute of Technology. Since completing his Ph.D. in physical chemistry at the University of California, Berkeley, Dr. Molina has received many honors and awards, including ele ction to the National Academy of Sciences, and selection as a Pew Scholar on Conservation and the Environment. He has also served as an advisor to the National Aeronautics and Space Administration, the National Science Foundation, and the National Institu tes of Health.

    I'd be pleased to do that, Mr. Vice President. The "greenhouse effect" is a process that affects the heat patterns of our planet. The earth receives energy from the sun, which passes relatively freely through the atmosphere. But the energy that the earth emits back to outer space is actually trapped by certain gases in the earth's atmosphere, which affects the earth's heat patterns. One of these gases is carbon dioxide, which is the most important greenhouse gas. And what we have in the figure is a repres entation of the amount of carbon dioxide in the atmosphere going back in time 160,000 years. The levels of carbon dioxide range between about 190 and 280 parts per million. We know this from measuring the composition of air bubbles trapped in ice cores fr om Antarctica and Greenland. The lower curve in the figure is a similar record of temperature going from the present back 160,000 years. There is a remarkably large correlation between these two curves. You can see that the preindustrial amounts of CO2 ar e below 300 parts per million. The current concentration of CO2 is roughly 365 parts per million. What is striking is that this is a level that we haven't seen before, certainly not in the past 160,000 years, and we got there very fast.

    The next question is where are we heading? What happens in the future depends on what we do. If we continue with the so-called "business-as-usual" scenario, we can predict that we are going to reach levels of about 700 parts per million. And what is rema rkable is how fast this would occur in only the blink of an eye on the geological or evolutionary time scale. I should point out that the earth has actually seen such high levels of carbon dioxide in the past, but that was some 50 million years ago when the earth was a very different place from what it is now. This is the sort of evidence that makes the scientific community consider this to be a serious problem. The magnitude and the pace of change are what make us really worry.


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