Leading climate scientists agree on the urgent need to drastically reduce carbon emissions on a global scale.

Human activity since the start of the industrial revolution has already added more than 530 billion*[1] tonnes of carbon (BtC) to the atmosphere, in the form of the greenhouse gas carbon dioxide (CO2), largely from the burning of fossil fuels including natural gas. The vast majority of this CO2 remains either in the atmosphere, where so far it has caused just under 1°C of global warming, or in the top layer of the ocean, where it has caused serious acidification.

The September 2013 report of the UN Intergovernmental Panel on Climate Change (IPCC) concluded that to have a 66% chance that eventual global warming will remain beneath 2°C, mankind must not emit any more than 470 BtC over the next few hundred years. The limit is even smaller (270 BtC) when the warming effect of other greenhouse gases are accounted for. But 2°C is now considered to lie on the boundary between dangerous and extremely dangerous warming.

The scale of the problem facing humanity is starkly evident when it is realised that in 2011 annual global emissions, mainly from burning fossil fuels, reached a record 9.5 BtC, 3% greater than in 2010. Furthermore, if all proven reserves of oil, gas and coal were burnt that would add about 780 BtC to the atmosphere as CO2! Thus to avoid very dangerous global warming most of the remaining fossil fuels, including shale gas, must stay in the ground for the foreseeable future and generally it is imprudent to continue extracting more fossil fuels.

A 2013 report shows that even if carbon capture and storage becomes widely available it is unlikely to make a significant impact in reducing global emissions. It may even be necessary to find ways of ‘sucking out’ much of the CO2 which has been added to the atmosphere in recent years.

[1] 1 billion = 1000 million

Last updated Dec 2013

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