A warming rate of more than 0.2 °C per decade is intolerable if the earth's ecosystems are to adapt, according to The German Advisory Council on Global Change. CICERO scientists adopted this rate and calculated that in order not to exceed it, cumulative emissions in the period 2010-2030 must not exceed approximately 190 gigatonnes of carbon (GtC).

"The implications are that global emissions must peak around 2015 and be cut by roughly half between the peak and the year 2030," Steffen Kallbekken, scientist at CICERO, said.

In a new paper in Nature Reports Climate Change, Steffen Kallbekken, Nathan Rive, Glen P. Peters and Jan S. Fuglestvedt from CICERO Center for International Climate and Environmental Research -- Oslo, argue for a new type of climate target to be considered:

"Focusing climate policy on a long-term target, such as the EU 2-degree target, provides limited guidance for mitigation over the next few decades, and gives the impression that there is time to delay," said Kallbekken.

The researchers propose that, in addition to a long-term cumulative emissions budget, a maximum limit on the rate of warming should also be considered as an element in the design of climate policies.

Required mitigation rates are 4-8 percent per year, which far exceeds anything achieved in history. "A short-term target provides clearer guidance on mitigation in the near term, limits potentially dangerous rates of warming, and allows easier inclusion of potent and toxic short-lived climate components," Kallbekken said.

"A short-term cumulative emissions target, for example 190 GtC for the period 2010-2030, is a useful approach to limit the rate of warming, while at the same time keeping the focus on what matters in the long term: reducing CO2 emissions."

(ScienceDaily*, 28/12/2009)

*Adapted from materials provided by Centre for International Climate and Environmental Research (CICERO).

Journal Reference:

   1. Steffen Kallbekken, Nathan Rive, Glen P. Peters & Jan S. Fuglestvedt. Curbing emissions: cap and rate. Nature Reports Climate Change, Published online: 19 November 2009 DOI: 10.1038/climate.2009.121