Long-term temperature data establishes the 1990’s as the warmest decade and 1998 as the warmest year since reliable records were kept beginning in 1861. Paleoclimatological data suggests that the 1990’s were the warmest decade in 1,000’s of years. Scientists are increasingly certain that the warming trend results from increased greenhouse gas concentrations in the atmosphere. This is not a natural increase; the Intergovernmental Panel on Climate Change, the lead international body of scientists studying the issue of climate change, believes with 90% certainty that human activity is at least partly responsible for the recent warming trends.
So far most of the warming has occurred in Northern Canada and Siberia and at night. These warming trends—while not very severe yet—can have negative effects on a global level. Increased temperatures in the Northern regions could lead to a melting of polar ice. In turn, melting polar ice could cause sea levels to rise. Increased temperatures could also force changes in regional agricultural practices.
Much of the controversy surrounding global climate change deals with the effects that natural processes—such as cloud formation and varying levels of solar radiation—have on global warming. A greater scientific understanding of the mechanics of global climate change, coupled with a consistent warming trend observed over the last 50 years, has convinced most scientist that global climate change is a very real threat.