A very simple question for this short post: what length pause (trend < 0) in global mean surface temperature could be simulated in a warming climate?
Several studies have suggested that around 5% of 10-year periods could show a cooling trend in future climate projections. Some examples have even shown periods of 17 years length can show a temporary cooling.
The figure below shows a period of 24 years with a (just) negative trend in a simulation which increases CO2 at 1% per year, using the FAMOUS GCM. This simulation is one of 96 identical simulations which only differ in a tiny perturbation (‘butterfly effect’) in the initial conditions. Several periods with negative trends lasting longer than 20 years are seen in this ensemble.
The magnitude of interannual variability in FAMOUS is likely a bit larger than observations, so this length of trend should not necessarily be considered possible in the real climate system, but exploring the mechanisms for the causes of the trend will certainly be of interest. Does the heat go into the deep ocean or is there a cloud effect affecting the top of atmosphere radiative balance?
More on these simulations to follow in a future post!