In his Dec. 18 letter to the editor, Steve Singleton cites examples of "natural" glacial advances during the Little Ice Age and glacial retreat due to "rising temperatures" in the late 1800s as evidence that "worldwide glaciers continuously advance and retreat with absolutely no evidence of linkage to CO2 concentrations in the atmosphere."
Truly, factors other than atmospheric carbon dioxide levels, such as fluctuations in volcanic activity, cyclic lows of solar radiation, changes in ocean circulation and others have the potential to alter global climate and, in turn, glacial activity.
However, by Singleton's own admission, temperature plays an important role in the behavior of glaciers: the higher the temperature, the more glaciers tend to melt overall.
Yet regardless of whether past glacial activity has been driven primarily by atmospheric CO2 concentrations, CO2 is known to warm the atmosphere, and warmer conditions lead to glacial retreat when ablation exceeds accumulation.
The warming properties of CO2 were discovered in the 1800s, when John Tyndall identified carbon dioxide as one of "the best absorbers of heat radiation" in the atmosphere, along with water vapor and ozone. He found that "even in small quantities, these gases absorb much more strongly than the atmosphere itself," a claim that has been verified by multiple laboratory experiments since (Herzberg 1953, Burch 1962, Burch 1970, etc.).
Further, Tyndall completed his work long before a scientist could have conceivably been fabricating evidence for use in the modern green movement.
Thus, that CO2 warms the atmosphere is a fact which has been scrutinized for over a century using the scientific method, not a part of an "international extortion attempt," as Singleton claims.
Additionally, Singleton contends the "worldwide results indicate that there is no common global trend of increasing glacier melt in recent years," explaining that, while some glaciers are shrinking and others are in equilibrium, "Scandinavian glaciers are growing."
However, Singleton's argument fails to include an admission that the overall rate of glacial advance does not match the rate of glacial retreat.
Instead, according to the World Glacier Monitoring Service, glaciers are losing mass on average, a phenomenon which "leaves no doubt about the ongoing climatic forcing resulting from the change in climate."
Singleton's emphasis on local small scale glacial advance rather than global trends in glacial retreat is akin to the importance of discerning climactic patterns rather than narrowly focusing on the behavior of weather.