Impacts and Issues

Modeling climate change is in its infancy. Climate involves many interactions between environmental forces, and some are not completely understood. So, building a computer model that mimics climate and thus can be used to investigate the likelihood of an abrupt climate change is not possible as of early 2008.

However, an understanding of the past is helpful in the present. The relationship between changes of atmospheric CO2 and periods of cooling and heating remains relevant. CO2 is a greenhouse gas-one of the compounds that increases the tendency of the atmosphere to retain heat. Measurements taken over the past 150 years clearly show that the CO2 level in the atmosphere is increasing.

This increase has not been constant over time, but rather has begun to accelerate. Whether this could help tip the atmosphere into an abrupt climate change is not clear and is very debatable. However, the majority of scientists now share the view that human activities increase the likelihood of the occurrence of climate change.

According to a 2002 report issued by the National Academy of Sciences, an abrupt climate change is not only possible but likely in the future. The report warned that such a rapid change of climate would greatly affect both ecosystems and societies.

An abrupt climate change would cause an upheaval in the lives of many people. For example, increased drought in agricultural regions could decrease food and water supplies.Aside from the hardship to everyday survival, climate change could increase the animosity between ‘‘have’’ and ‘‘have-not’’ countries.

The U.S. military has recognized the possible security implications of such a destabilized world. Paradoxically, some scientists envision that the present-day warming of the atmosphere could tip Earth into another Ice Age, since the distribution of heat via the ocean conveyor would break down.

This could cause cooling of the Northern Hemisphere. The portion of the ocean conveyor that circulates through the North Atlantic region has been identified as particularly important, since the melting of the polar ice cap could send enough freshwater into this region to diminish or perhaps even halt ocean currents such as the Gulf Stream.

A report in a 2002 issue of Nature documented the decreasing salinity of the North Atlantic since the 1960s, even to depths of 13,000 ft (about 4,000 m). Whether this has begun to affect the conveyor is unclear as of early 2008.

A plan spearheaded by the Woods Hole Oceanographic Institution and other agencies to deploy thousands of remote sensors throughout the global ocean could help to better understand the state of the ocean and the influence of global warming.