Research Highlights

Nature Reports Climate Change
Published online: 2 April 2009 | doi:10.1038/climate.2009.31

Road to recovery

Olive Heffernan

Environ. Res. Lett. doi:10.1088/1748-9326/4/1/014012 (2009)

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Recovering from dangerous levels of global warming may be even harder than anticipated, finds new research. Although there is no consensus on what constitutes a 'dangerous' level of climate change, the European Union has adopted a target of limiting warming to less than 2 °C above pre-industrial levels.

Now, Jason Lowe of the UK Met Office and colleagues estimate how long it would take to return to acceptable levels of warming if this threshold is exceeded. Using a simple climate model, Lowe and colleagues find that if greenhouse gas emissions peak in 2015 and subsequently decline at a compound rate of three per cent per year, there is a 55-per-cent chance of exceeding the 2 °C target. Moreover, there is a 30-per-cent chance global temperatures will remain above 2 °C for 100 years and a 10-per-cent chance they will still be above 2 °C 300 years from now.

The study is the first to use a state-of-the-art general-circulation model with an integrated carbon cycle to test the skill of simple models in analysing 'overshooting' scenarios for climate policy. It suggests that once a safe level of warming is exceeded, even very large and rapid reductions in emissions will result in only a gradual decline in global temperatures.