MEMBERS OF THE scientific community by and large concur that the Earth is undergoing a change in climate and that global warming is occurring at an increasing rate. In fact, scientific modeling suggests that Earth will experience an increase in temperature during the next 100 years at a pace up to four times greater than that in the previous 100 years. To a large extent this acceleration in the late 20th century is attributed to carbon dioxide (CO2) emissions generated by human activity. Carbon dioxide acts like a glass barrier over the Earth, preventing heat from leaking into the environment, and thus creating a greenhouse effect. Human activity has counteracted global warming to a small degree by emitting aerosols in the environment, causing global cooling.

Volcanism ...