Make Me Smarter
RICHARD BRILLSunday, June 10, 2001
Now that it's almost summer, we may be feeling the effects of global warming. At first glance it might seem like an easy thing to decide if our planet is heating up. This is far from the case. Even if we can determine that global climate change is taking place, it is another thing altogether to determine the cause and to determine which, if any, of our human activities are responsible for it.
Waiting to take action
on global warming
In the first place, taking Earth's temperature is not merely a simple matter of sticking a thermometer in the ground and waiting a few minutes like we do when we take our own temperature.
The earth's temperature results from a complex system of heat transfer. Heat is received from the sun, is distributed over the surface, oceans and atmosphere, and re-radiated into space. The temperature at any given place and time is highly variable and depends on many factors. This is especially true on land where temperature changes are more rapid and more extreme than at sea.
One of the best indicators of Earth's overall temperature is the average temperature of water in the ocean. Water resists changes in temperature, and so the ocean shows a smaller range of temperature changes and extremes compared to land areas. But collecting sufficient data for sea temperatures is an expensive and difficult process.
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The second problem is that the overall average temperature of Earth changes only a small amount over short time intervals. We don't know how much of a temperature change is significant and how much of a change it would take to cause a major climatic disaster. It is estimated that the earth's temperature was different by a only few degrees during the last glacial period when ice 2 miles thick covered the surface from polar regions to around 40 degrees latitude.
The third problem is that climate fluctuates due to natural processes that are not completely understood. These take place on a time scale that dwarfs a human lifetime. In the past, some of the major climatic changes were the result of drifting continents, changes in ocean currents, emerging mountain ranges or asteroid/comet impacts. The record of global temperatures even over the past thousand years looks like the graphs of stock market prices, with many sharp declines and advances. As with the stock market, it is impossible to say whether any given surge, up or down, represents a trend or merely a small adjustment. Only by following the changes over long periods can the pattern, if any, be discerned.
As much as we do know about our planet, and despite the tremendous knowledge gained in the past two decades, we still don't know enough about the earth and its systems to make definitive statements. We don't know and can't predict the exact effects of pollution on the climate system, and we can't say for sure what the effects of long-term climate change might be on sea level, agriculture and politics.
What we do know is that throughout its history the earth has been either colder or warmer than now. We know there has been an alarming rise in Earth's temperature and in sea level in the 20th century. We know that increased global temperature will result in rising sea level, changes in rainfall and climate, changes in agriculture and increasing political tensions.
Some of our leaders think we should wait until the computer models more uniformly predict disastrous consequences before taking action. This does not represent sound policy. What might have been the outcome if public health measures had awaited the discovery of "germs" before being implemented in the 19th century?
It's something to think about. But remember, to understand requires knowing the facts of the matter.
Richard Brill, associate professor of science at
Honolulu Community College, teaches earth and physical science,
and investigates life and the universe. If you have questions about
this world we live in, e-mail them to firstname.lastname@example.org.