Targets must tackle global warming rate
26 November 2010
The upcoming UN Climate Change Conference in Cancun will fail to meet its objectives unless it addresses not just how much the planet warms, but also how fast it warms, a new study argues. Potentially dangerous rates of global warming could outpace the ability of ecosystems and manmade infrastructure to adapt. The study shows that to achieve their aims, negotiators must limit the maximum global emission rate as well as the total amount of carbon emitted through to 2200.
The research, led by Oxford University scientists, appears in a special report on ‘Four degrees and beyond: the potential for a global temperature increase of four degrees and its implications’ published today in Philosophical Transactions of the Royal Society A. The publication coincides with the start of the UN Climate Change Conference in Cancun, Mexico (29 November-10 December).
‘Many people think that the reason why emissions need to peak soon is to save the climate of the 22nd century, but our research highlights a more immediate reason,’ explains Niel Bowerman of the Oxford University’s Department of Physics, who led this study. ‘Our study shows we need to start cutting emissions soon to avoid potentially dangerous rates of warming within our lifetimes, and to avoid committing ourselves to potentially unfeasible rates of emission reduction in a couple of decade’s time.’
‘Peak warming is determined by the total amount of carbon dioxide we release into the atmosphere, not the rate we release it in any given year,’ said Dr Myles Allen of Oxford University’s Department of Physics and a co-author of the study. ‘Dangerous climate change, however, also depends on how fast the planet is warming up, not just how hot it gets, and the maximum rate of warming does depend on the maximum emission rate. It’s not just how much we emit, but how fast we do so.’
‘This paper finds that to keep the most likely rate of carbon-dioxide-induced warming below 0.2°C per decade carbon dioxide emissions need to peak below 11.5 billion tonnes of carbon per year,’ said Dr Allen. ‘0.2°C per decade is regarded by some as an upper limit to adaptation for many systems, indeed some ecosystems, may be unable to adapt to even half this rate. Current emissions from fossil use, cement manufacturing and land use change are estimated to be 9.6 billion tonnes of carbon per year, up from 8 billion tonnes per year in 2000.’
At the Cancun conference, politicians will be discussing emission targets for 2020 and 2050 with the aim of limiting global warming to not more than two degrees Celsius. The new study found that setting targets for the peak rate of emission and total cumulative emissions to 2200 would be a much better way of framing an evidence-based policy for carbon dioxide emissions. It also finds that the case for early emission reductions rests not on the long-term temperature target, but on the need to avoid potentially dangerous rates of warming over the next few decades, and dangerous commitments to future rates of emission reduction.
For more information contact Niel Bowerman of Oxford University on +44 (0)7912 614 541 or Dr Myles Allen of Oxford University on mobile; +44 (0)7776 306691 or email myles.allen@physics.ox.ac.uk
Alternatively contact the University of Oxford Press Office on +44 (0)1865 283877 or email press.office@admin.ox.ac.uk