Change in Annual Mean Sea Surface Temperature under Four Emissions Scenarios

In 2001, a report by the Intergovernmental Panel on Climate Change associated observations of global warming with increased concentrations of greenhouse gases in the earth’s atmosphere. That report, Climate Change 2001, noted that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.” The report also noted that carbon dioxide and other gases produced by human activities would continue to affect the climate system.

In modeling future climates, researchers take into account the atmospheric concentration of greenhouse gases. These maps show four possible climate futures for the United Kingdom. Each scenario assumes a different concentration of carbon dioxide in the atmosphere. Under the low-emission scenario, concentrations of carbon dioxide reach about 540 ppm by 2100, (ppm means parts per million, or parts of carbon dioxide per million parts of atmosphere sampled). That's nearly twice the pre-industrial concentration of about 280 ppm. Under the high-emission scenario, carbon dioxide concentrations reach 920 ppm by 2100.

These scenarios indicate that more carbon dioxide in the atmosphere leads to greater temperature change. The scenarios also indicate that climate change will not be uniform.