Climate Change Science
For over the past 200 years, the burning of fossil fuels, such as coal and oil, and deforestation have caused the concentrations of heat-trapping "greenhouse gases" to increase significantly in our atmosphere. These gases prevent heat from escaping to space, somewhat like the glass panels of a greenhouse.
Greenhouse gases are necessary to life as we know it, because they keep the planet's surface warmer than it otherwise would be. But, as the concentrations of these gases continue to increase in the atmosphere, the Earth's temperature is climbing above past levels. The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) shows that the Earth's average surface temperature has risen by 0.76° C since 1850. Most of the warming over the past 50 years is very likely to have been caused by emissions of carbon dioxide (CO2) and other 'greenhouse gases' from human activities.
Without action to reduce these emissions, the global average temperature is likely to rise by a further 1.8-4.0°C this century, and by up to 6.4°C in the worst case scenario, the IPCC projects. Even the lower end of this range would take the temperature increase since pre-industrial times above 2°C - the threshold beyond which many scientists believe irreversible and possibly catastrophic changes would become more likely.
The Intergovernmental Panel on Climate Change (IPCC) is an international group of experts formed in 1988 reviews scientific research and offers assessments of climate change and its effects.