Is a New Ice Age Coming?
In Chapter 8, I mentioned a theory that global warming could lead to another ice age. Terrance Joyce, a respected scientist specializing in physical oceanography, explains how global warming can cool parts of the Earth, and he gives some interesting historical examples. The Gulf Stream normally carries warm water from the tropics past the East Coast of the United States and on to Europe, substantially warming the atmosphere in both regions. Part of the driving force that propels this circular ocean current is the sinking of heavy salty water from the warm tropical ocean to great depths in northern regions. This phenomenon is similar to a conveyor belt. Whenever too much fresh water is added to this stream, for example from melting Arctic ice, the North Atlantic water becomes less salty and less dense, thus slowing or altering the Gulf Stream current. Joyce proposes that about 500 years ago changes in this ocean current were responsible for cooling the climate in northern Europe and in
