Climate Change State of Knowledge

Burning coal, oil and natural gas to heat our homes, power our cars, and illuminate our cities produces carbon dioxide and other greenhouse gases as by-products. Deforestation and clearing of land for agriculture also release significant quantities of such gases.

Over the last century, we have been emitting greenhouse gases to the atmosphere faster than natural processes can remove them. During this time atmospheric levels of these gases have climbed steadily and are projected to continue their steep ascent as global economies grow.

Records of past climate going as far back as 160,000 years indicate a close correlation between the concentration of greenhouse gases in the atmosphere and global temperatures. Computer simulations of the climate indicate that global temperatures will rise as atmospheric concentrations of carbon dioxide increase.

The 1995 report of the Intergovernmental Panel on Climate Change, which is the most comprehensive and thoroughly reviewed assessment of climate change science ever produced, concluded that change is already underway. The Intergovernmental Panel, which represents the work of more than 2000 of the world’s leading climate scientists, concluded that Earth has already warmed about 1 degree Fahrenheit over the last century, and that “the balance of evidence suggests that there is a discernible human influence on global climate.

The Intergovernmental Panel estimates that global surface air temperature will increase another 2 to 6.5 degrees Fahrenheit in the next 100 years. The difference in temperature from the last ice age to now is about 9 degrees Fahrenheit. Their “best guess” is that we will experience warming of about 3.5 degrees Fahrenheit by 2100 which would be a faster rate of climate change than we have experienced in the last 10,000 years, the period in which modern civilization developed.

Warming of this magnitude will affect many aspects of our lives as it changes temperature and precipitation patterns, induces sea level rise, and alters the distribution of fresh water supplies. The impacts on our health, the vitality of forests and other natural areas, and the productivity of agriculture are all likely to be significant.

As the risks of global climate change become increasingly apparent, there is a genuine need to focus on actions to reduce our greenhouse gas emissions and minimize the adverse impacts of a changing climate.

From Climate Change – State of Knowledge
Office of Science and Technology, October 1997 – PDF

Intergovernmental Panel on Climate Change
US Global Change Research Program

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