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Temperature change 1765-2100: Graph excerpted from the IPCC's Third Assessment Report showing past and predicted changes to global temperature.
Enlarge ImageHow we are changing the climate
For more than a century, people have relied on fossil fuels such as oil, coal and gas for their energy needs. Burning these fossil fuels releases the global warming gas carbon dioxide into the atmosphere. Other, even more potent, greenhouse gasses are also playing a role, as is massive deforestation.
"The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action."
-- Joint statement by 11 national science academies to world leaders (full text)
What we know
While there are still uncertainties, particularly related to the timing, extent and regional variations of climate change, there is mainstream scientific agreement on the key facts:
- Certain gasses, such as carbon dioxide, in the atmosphere create a "greenhouse effect", trapping heat and keeping the Earth warm enough to sustain life as we know it.
- Burning fossil fuels (coal, oil, etc.) releases more carbon dioxide into the atmosphere. Although not the most potent greenhouse gas, carbon dioxide is the most significant in terms of human effects because of the large quantities emitted.
- Carbon dioxide concentrations in the atmosphere are now the highest in 150,000 years.
- The 1990's was most likely the warmest decade in history, and 1998 the warmest year.
There is also widespread agreement that:
- A certain amount of additional warming - about 1.3º Celsius (2.3º Fahrenheit) compared to pre-industrial levels - is probably inevitable because of emissions so far. Limiting warming to under 2° Celsius (3.6°F) is considered vital to preventing the worst effects of climate change.
- If our greenhouse gas emissions are not brought under control, the speed of climate change over the next hundred years will be faster than anything known since before the dawn of civilization.
- There is a very real possibility that climate feedback mechanisms will result in a sudden and irreversible climate shift. No one knows how much global warming it would take to trigger such a "doomsday scenario".
Links:
Intergovernmental Panel on Climate Change
IPCC Third assessment report
Climate Action Network (CAN) – “Preventing Dangerous Climate Change” – Position Paper (pdf)
Implications of the IPCC third assessment report – Greenpeace briefing
New Scientist magazine special climate change section
National Geographic special climate change section
