Science

The Greenhouse Effect

The Earth receives energy from the sun in the form of shortwave radiation. This is largely absorbed by the earth and reradiated back out towards space at much longer wavelengths. This long wave radiation is absorbed by greenhouse gases such as CO₂ and keeps the earth warm. More gases mean more warming.

Recorded CO₂ Increases

Greenhouse gases have been rising since the onset of the industrial revolution and are currently about 379 parts per million (ppm) compared to a pre-1850 concentration of 280 ppm.

Recorded Temperature Increases

Over the 20th Century global average surface temperatures have increased by 0.74°C but some locations have witnessed a local increase in excess of 2°C.

Projected CO₂ Increases

Greenhouse gases are predicted to continue rising over the coming century. Some projections put the CO₂ concentration by 2100 as high as 950 ppm, an increase of 670 ppm.

Projected Temperature Increases

This increase in CO₂ concentration is predicted to cause an increase in global air temperature of between 2°C to 4.5°C with a best estimate of about 3°C. An average rise of 2°C is accepted by many as the threshold for unacceptable and unpredictable impacts on the planet.

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