Headlines from the IPCC’s recent findings (September 2013):
- Global scientists have found that to hold warming to 2C, total emissions cannot exceed 1,000 gigatons of carbon. Yet by 2011, more than half of that total “allowance” – 531 gigatons – had already been emitted.
- To ensure the budget is not exceeded, governments and businesses may have to leave valuable fossil fuel reserves unexploited. “There’s a finite amount of carbon you can burn if you don’t want to go over 2C,” Stocker told the Guardian. “That implies if there is more than that [in fossil fuel reserves], that you leave some of that carbon in the ground.”
- This raises key questions of how to allocate the remaining “carbon budget” fairly among countries, an issue that some climate negotiators fear could wreck the UN climate talks, which are supposed to culminate in a global agreement on emissions in 2015.
Their other key findings in the report – the first such assessment since 2007 and only the fifth since 1988 – included:
- Atmospheric concentrations of carbon dioxide, methane and nitrous oxide are now at levels “unprecedented in at least the last 800,000 years”.
- Global temperatures are likely to rise by 0.3C to 4.8C by the end of the century depending on how much governments control carbon emissions.
- Sea levels are expected to rise a further 26-82cm (10-32in) by 2100. The wide variation in part reflects the difficulty scientists still have in predicting sea level rises.
- The oceans have acidified, having absorbed about a third of the carbon dioxide emitted.