The Earth’s climate is a complex system, derived from a combination of natural and human induced properties. Climate change results from an interplay of radiation from the sun, the circulation of water in oceans, the growth of trees and other plants, changes in land use, and changes in the combination of gases that form the atmosphere. Some of these gases help regulate the amount of energy and heat that escape from the atmosphere, commonly referred to as greenhouse gases (GHG) (glossary). The most critical GHG is carbon dioxide (CO2). While CO2 occurs naturally, concentrations of CO2 in the atmosphere have been increasing as a result of human activity - principally the burning of fossil fuels: coal, oil and gas in automobiles, power plants, and factories. This increase of CO2 - often expressed in terms of carbon emissions - has mirrored the huge growth of industrial activity of the last 100 years.

Climate change is now regarded by the world's scientists as one of the most serious global problems the world faces.

The Intergovernmental Panel on Climate Change (IPCC) convened by the United Nations in 1988, brought together thousands of the world's preeminent atmospheric scientists to assess the peer reviewed scientific literature on climate change. The IPCC study was a part of the objective to develop a consensus on scientific and other technical issues to inform governments that were developing climate change policies. The IPCC 1995 Second Assessment Report revealed that the increased concentrations of CO2 and other gases - such as methane and nitrous oxide - as well as other changes to the earth’s surface, have altered the climate. According to the IPCC, "the balance of the evidence suggests a discernible human influence on the global climate". This alteration manifests itself in the form of global warming. The Earth is thought to have warmed anywhere from 0.3 to 0.6 degrees Celsius over the last 100 years.

 The IPCC has projected a number of different changes to the "future climate" depending on the sensitivity of the climate system and the rate of continued pollution from human activity. If CO2 emissions continue at anything like the current rate, by the year 2100 concentrations of CO2 in the atmosphere will more than double and the global average temperature will increase by anywhere from1 degree C. to 3.5 degrees C. While this increase may not sound dramatic, any increase within that range would constitute the largest increase within the last 10,000 years.

 The impacts of temperature changes will be devastating: a rise in sea levels all around the world; an increase in extremely hot and extremely cold days; increased occurrence of droughts and flooding; more extreme rainfall events with the possibility of an increase in the occurrence and intensity of tropical storms and cyclones; an expansion in the range and incidence of serious diseases and other direct impacts on human health; as well as a loss of countless plant and animal species. Additional rapid increases in CO2 emissions could also slow down or stop the ocean circulation system that brings Europe its mild climate. Climatic changes such as these could disrupt entire ecosystems as well as agricultural and economic activity.

 While CO2 and other greenhouse gasses will continue to naturally exist in the Earth's atmosphere, the unprecedented concentrations due to industrialization over the last 150 years is something humans can control. Today networks like CAN represent a unified voice for change. Environmental groups have banded together to find solutions to reducing humans' contribution to global warming.

 Links and References

Travel to the United Nations Framework Convention on Climate Change's (UNFCCC) page which has an information kit including everything to understanding climate change to dealing with the consequences, facts on the international conventions and advice on how to reduce greenhouse gas emissions.
 http://www.unfccc.de/resource/iuckit/index.html

Common Questions about Climate Change Answered by United Nations Environment Programme and the World Meteorological Organization http://www.gcrio.org/ipcc/qa/cover.html

The United States Environmental Protection Agency's take on what climate change is and what is known about it.
http://www.epa.gov/globalwarming/climate/

Environmental Defense has a general fact sheet containing valuable information on global warming and climate change. Written in July 1999 it is an up to date account of what climate change is and what causes it. http://www.environmentaldefense.org/pubs/FactSheets/o_GW.html

Greenpeace International has compilied an extensive list of frequently asked questions regarding climate change and answered them in simple, frank terms. Find it at
http://www.greenpeace.org/~climate/