Study: Would take 25-30 years OR LONGER to see if carbon cuts had ANY effect

E&E News reports:

If the countries of the world reduced their greenhouse gas emissions today enough to keep the world from warming more than 2 degrees Celsius, when would they be able to tell that these efforts had succeeded?

That’s the basic question posed in a paper released yesterday in the journal Proceedings of the National Academy of Sciences.

The answer: about 25 to 30 years, at least where global temperatures are concerned. On a regional level, it may take even longer to see the changes, the paper states.

To those who care about curbing the negative impacts of climate change, this suggests there is no time like the present to start curbing emissions.

Read more… ($ubscription required).

Study abstract below.

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Delayed detection of climate mitigation benefits due to climate inertia and variability

Claudia Tebaldia,1 and Pierre Friedlingsteinb
aClimate Central and National Center for Atmospheric Research, Boulder, CO 80307; and bCollege of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter EX4 4QJ, United Kingdom
Edited by Benjamin D. Santer, Lawrence Livermore National Laboratory, Livermore, CA, and approved September 6, 2013 (received for review January 1, 2013)

Climate change mitigation acts by reducing greenhouse gas emis- sions, and thus curbing, or even reversing, the increase in their atmospheric concentration. This reduces the associated anthropo- genic radiative forcing, and hence the size of the warming. Because of the inertia and internal variability affecting the climate system and the global carbon cycle, it is unlikely that a reduction in warm- ing would be immediately discernible. Here we use 21st century simulations from the latest ensemble of Earth System Model experiments to investigate and quantify when mitigation becomes clearly discernible. We use one of the scenarios as a reference for a strong mitigation strategy, Representative Concentration Pathway (RCP) 2.6 and compare its outcPome withNeither RCPA4.5 or RCPS8.5, mitigation signal by 2035 or 2045, depending on whether the comparison is with RCP8.5 or RCP4.5, respectively. The detection of climate benefits of emission mitigation occurs later at regional scales, with a median detection time between 30 and 45 y after emission paths separate. Requiring a 95% confidence level induces a delay of several decades, bringing detection time toward the end of the 21st century.