Climate Change

The climate on the earth depends on a number of factors, including the mix of gases in the atmosphere, the amount of energy the Earth receives from the sun, and the conditions at the Earth's surface.

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The examination of ice cores from the arctic region indicate at least four periods over the past half million years when there have been relatively high levels of CO₂ in the atmosphere. These have corresponded to warm periods.¹

Since the early 1800s, atmospheric concentrations of carbon dioxide have increased nearly 30%, and the concentrations of other greenhouse gases like methane (more than doubled) and nitrous oxide (up by about 15%) have also increased.²

Scientists agree that CO₂ levels in the atmosphere are currently high and are increasing.³ Scientists also agree that the average annual temperature at the surface of the Earth has increased by about one degree Fahrenheit over the past 150 years.³

The greenhouse effect traps the heat energy that drives the Earth's weather and climate. Continuing growth in the level of greenhouse gases in the atmosphere and a variety of other observations are together raising concerns that the Earth's climate is changing.³

References:

1. www.geocraft.com/WVfossils/last_400k_yrs.html (accessed November 2004).
   
2. www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html (accessed November 2004).
   
3. www.ipcc.ch/pub/un/syreng/spm.pdf (Intergovernmental Panel for Climate Change, Summary for Policy Makers, accessed August 2006).