This is a response to the letter to the editor, "Temperature increase 'virtually insignificant.'"
The writer mentions "data from Arctic and Antarctic ice samples." There are no dated "ice samples" from the Arctic, which is floating sea ice only a few meters thick. Samples come from ice cores obtained by drilling thousands of meters into the Greenland and the Antarctic glaciers. There are two cores from Antarctica, a 400,000-year core and an 800,000-year core. Yes, there are fluctuations in the carbon dioxide levels from a low of 170 parts per million to a high of 298.6 ppm. The core ends in 1950.
Since 1958, measurements have been taken from the atmosphere over Mauna Loa, Hawaii. Initial reading was 316 ppm of carbon dioxide. There has never been an annual decrease, and now values have topped 400 ppm.
The significance of the ice cores is not that the carbon dioxide values fluctuate, but that present carbon dioxide level in the atmosphere is about 33 percent greater than at any time in the last 800,000 years. And the rate of increase is becoming more rapid. This is the reason for global warming.
Donald B. Krall
Lower Macungie Township
The writer is a retired professor
of geology from Kean University.