In the hungry fires of industry, modern man burns nearly 2 billion tons of coal and oil each year. Along with the smoke and soot of commerce, his furnaces belch some 6 billion tons of unseen carbon dioxide into the already tainted air. By conservative estimate, the earth's atmosphere, in the next 127 years, will contain 50% more CO<SUB>²</SUB>
This spreading envelope of gas around the earth, says Johns Hopkins Physicist Gilbert N. Plass, serves as a great greenhouse. Transparent to the radiant heat from the sun, it blocks the longer wave lengths of heat that bounce back from the earth. At its present rate of increase, says Plass, the CO<SUB>²</SUB> in the atmosphere will raise the earth's average temperature 1.5° Fahrenheit every 100 years.
As the blanket of CO<SUB>²</SUB> gets thicker, it also prevents the tops of clouds from losing heat as rapidly as before. The smaller temperature difference between cloud base and top cuts down the air currents which must circulate through the cloud before rain or snow can form. Lowered rainfall will make a drier climate. Less cloud cover will be formed, more sunlight will reach the earth, and the average temperature will rise still higher.
After thousands of years, says Professor Plass, plants and the slow-moving seas will absorb most of the excess CO<SUB>²</SUB>. But for centuries to come, if man's industrial growth continues, the earth's climate will continue to grow warmer.