Our world is warming: The ten hottest years since records began in 1850 have all occurred since 1996. And all of the 20 warmest years have occurred since 1980. Globally, 1998 and 2005 were the hottest years on record – followed by 2003, 2002 and 2004.*2

Averaged across the globe the temperature of the world has already warmed by about 0.8C since 1900.*3 By 2100 the world´s average temperature could increase by 1.6 to 6.9C above the 1850-1899 average.*4

Temperature changes in certain regions could be even higher. Already northern Africa, Spain and parts of Russia and China have seen temperatures rise by 1 to 2C*5 whilst Canada and Alaska are 3 to 4C warmer in winter than in the 1950´s.*6 That´s four to five times more than the global average temperature increase.

The world is warming due to the increase in greenhouse gases in our atmosphere due to human activities. The Earth´s natural greenhouse gases that comprise our atmosphere trap just enough of the sun´s heat making the world 30C warmer than it would otherwise be. Without these natural greenhouse gases our world would not be habitable. But now human activities are increasing the amount of heat trapping gases in our atmosphere.

Carbon dioxide is the most important greenhouse gas human activities emit. About 80% is emitted through the use of oil, coal and gas to supply the world´s energy. The other 20% is caused by land-use change. Primarily the cutting down of trees and vegetation that then release carbon.*7

Since the beginning of the industrial era humanity has released billions of tonnes of carbon dioxide into Earth´s fragile atmosphere. The amount of carbon dioxide in the atmosphere has now increased from a pre-industrial level of about 280 ppm*8 (280 parts of carbon dioxide to a million parts of air) to about 387 ppm*9. This is causing Earth´s temperatures to rise.

This graph shows temperature (blue line) and carbon dioxide concentrations in the atmosphere (CO2) (red line) over the past 420,000 years. The correlation between the two extends back 800,000 years before the present. By 2100 the amount of CO2 in Earth´s atmosphere could be (A) 1200 ppm with continued intensive fossil fuel use or (B) 350 ppm to 400 ppm if emergency globally co-ordinated policy action is taken now to arrest climate change. Credit: Petit, J.R. et al (1999) Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica´ Nature 399, 429-436

Antarctic ice core records show that over the past 800,000 the amount of carbon dioxide in the atmosphere has ranged between about 180 to 280 ppm which correlated with a change in Antarctic temperatures of about 12C.*10 Hence a 100 ppm change correlated with a 12C change in Antarctic temperatures. This century in the worst case scenario predicted today the amount of carbon dioxide in Earth´s atmosphere could rise to 1200 ppm with continued intensive fossil fuel use and an increasing population.*11 This would be nine times the 100 ppm change of the last 800,000 years which caused a 12C change in Antarctic temperatures.

However with emergency action taken now the world could keep the level of carbon dioxide in Earth´s atmosphere to 350-400 ppm by 2100-2150.*12 But we must act today.

Critical feedback

By 2030 trees, vegetation and soils are likely to absorb less carbon dioxide from Earth´s atmosphere.*13 Then as temperatures continue to rise forests and soils are expected to release escalating amounts of the carbon they store. This is critical as Nature’s carbon release will increase global warming, causing these sources to release yet more carbon in a self-perpetuating cycle known as a positive feedback.

Additionally up to 2000 billion tonnes of methane could also enter Earth’s atmosphere due to the melting of methane hydrates*14 – an ice like mix of methane, stored deep in the ocean’s seabed or closer to the surface in the Arctic.

To put it simply, if we do not rapidly reduce our own greenhouse gas emissions – and soon – we will release vast amounts of greenhouse gases from Nature’s own sources. If this occurs there will be nothing we can do to stop it.