Can We Stop Global Warming?
Harte, John, USA TODAY
Controlling population growth and cutting down on wasteful consumption of energy and other resources clearly are necessary to reverse the climatic extreme.
By the middle of the 21st century, the Earth probably will be warmer than it has been at any time in human history--possibly since the age of dinosaurs ended 65,000,000 years ago. The projected increase in the average ground-level temperature ranges from three to eight degrees Fahrenheit. This may not seem like very much. After all, if tomorrow's temperature is eight degrees higher than today's, you might not notice it. Let us place this climate change in perspective, though. Over the several thousand years of emergence from the last ice age and poleward retreat of the glaciers, the average global temperature increased by just a little more than eight degrees. So, scientists are projecting a warming that could be comparable to the total rise since the last ice age! Because this warming will take place over a mere 50 to 100 years, its rapid pace could stress life on Earth far more than did the glacial pace of the prehistoric warming.
Why is the warming occurring? How much can the predictions be trusted? What will be the consequences to society and to life on Earth? What can be done to reduce impending climate change?
The warming is occurring because humanity is affecting the atmosphere. Each year, billions of tons of carbon dioxide are being loaded into it, an inevitable consequence of the burning of coal, oil, and natural gas. In the atmosphere, carbon dioxide acts like a blanket, trapping heat and radiating some of it back down to Earth. This process of heat trapping is called the greenhouse effect.
The level of atmospheric carbon dioxide has increased by more than 25% since the beginning of the Industrial Revolution. Most of that rise is due to fuel burning, but it also has resulted from the massive deforestation that has occurred during the past 200 years and continues today as, worldwide, an area of tropical forest nearly the size of Pennsylvania is cut and cleared each year. Carbon, which constitutes about half the weight of wood, converts to carbon dioxide when felled trees either rot or are burned.
Carbon dioxide is the main contributor to the warming, but other heat-trapping gases (known as "greenhouse gases") include nitrous oxide, methane, and chlorofluorocarbons. Nitrous oxide comes from excessive use of nitrogen fertilizers in agriculture. Methane emanates from rice paddies and cattle feedlots. Chlorofluorocarbons, emitted from styrofoam manufacturing and other industrial processes, not only trap heat, but destroy the Earth's protective stratospheric ozone layer as well. Except for the internationally regulated chlorofluorocarbons, these gases are being emitted to the atmosphere at ever-increasing rates as the human population increases and the scale of energy use, industrial activity, and agriculture grows.
How fast will these greenhouse gases continue to build up in the atmosphere? The answer is not within the realm of scientific prediction--it depends entirely on human choices. Climatologists base their predictions of climate change on current knowledge of the physical behavior of the atmosphere and oceans. Not being good at predicting human behavior, they don't even try to do so.
Instead, they assume various possibilities, called scenarios, about the rate of buildup of the gases. For each scenario, a climate prediction is generated using climate models, called general circulation models, that are run on the world's largest and fastest computers.
Assuming that the current rates of growth of population and per capita fossil fuel use continue into the future, and that deforestation occurs at its current pace, greenhouse gases will build up extremely rapidly in the atmosphere--enough so that, about 40 years from now, a three to eight degree warming will occur. On the other hand, if the exponential growth of population and per capita energy use could be stopped, keeping total annual fuel consumption at current levels, this level of warming would be delayed by 50 years or more. …