Proc. Natl Acad. Sci. USA http://doi.org/n7p (2013)

Mitigation of greenhouse gas emissions should reduce their concentration in the atmosphere and thereby reduce warming. It is not known how long after mitigation there would be a sufficient change in atmospheric concentration to affect surface temperature, and detection of the mitigation effort would be hampered by natural variability in the climate system.

Claudia Tebaldi, of Climate Central and the National Center for Atmospheric Research, USA, and Pierre Friedlingstein, of the University of Exeter, UK, use climate projections to determine when mitigation efforts become detectable in surface temperature. They compare various emissions scenarios, from strong mitigation to business-as-usual, and the expected atmospheric CO2 concentrations and surface temperatures.

Their findings suggest that it takes at least 25 years for there to be a detectable temperature signal globally, with regional signals measurable after even longer lead times. Atmospheric CO2 concentrations, with smaller natural variability, can be detected within 10 years of mitigation.