Atmospheric CO2 Concentration in last 10000 years

Image by IPCC Working Group 1

Carbon Dioxide is the greenhouse gas that is having the most effect:

  • In 2005 Carbon Dioxide (CO2) had a concentration of 379 parts-per-million which is the highest it has been in the past 650,000 years. The concentration has been going up faster and faster.

  • The primary source of this rise in CO2 is from humankind burning fossil fuel, with a smaller contribution from changing the way land is used, e.g. cutting down forests.

  • Human production of CO2 continues to rise - approximately 23,500 million tonnes per year in the 1990s to 26,400 million tonnes per year after 2000.

Atmospheric Methane Concentration in the past 10000 years

Image by WG1 of Annual Report 4 from IPCC

Methane is another significant greenhouse gas:

  • In 2005 Methane (CH4) had a concentration of 1774 parts-per-billion which is about two and half times bigger than it has been over the previous 650,000 years.

  • It is very likely though not certain (more than 9/10 confidence) that this rise is man-made - mostly from human agriculture.

  • The overall effect of increasing Methane rise is about one quarter that of the rise in Carbon Dioxide.

  • It is thought that Methane is not growing as rapidly as it was.

Other greenhouse gases include:

Nitrous Oxide - which is growing at a steady rate. Only one third of this rise comes from human activity, mainly agriculture. Its effect is about 1/10 that of Carbon Dioxide.

Ozone and Halocarbons each produce an effect that is a quarter as bad as Carbon Dioxide.