An explanation for the supposed “hiatus” that is discussed in this news feature is that the rate of surface warming depends on the phase of the Pacific Decadal Oscillation (PDO). The PDO is a cycle that lasts a few decades, during which the Pacific will go through a phase of being warmer than normal, followed by a phase when it’s cooler than normal – illustrated in the figure below (taken from the Nature News Feature).
When the PDO phase is such that the Pacific is warmer than average, the surface temperatures rise quite quickly. When in the cool phase, the surface temperatures rise more slowly, or stall. This is shown below (taken from the Nature News Feature) and illustrates that the warm or cool phases could last for 20 – 30 years. The current slowdown/pause started about 16 years ago, and so some are suggesting that it could continue for another 10 – 15 years (maybe until 2030).
There is, however, an issue with the current slowdown persisting for as long as another 15 years. The figure below is from Hansen et al. 2011 and shows surface temperatures and planetary energy imbalances for three different models. If, as the figure above illustrates, there was a surface warming pause between 1945 and 1975, then the figure below indicates that the planetary energy imbalance increased – during that period – from around 0.1 Wm-2 to about 0.4 – 0.5 Wm-2. This is actually consistent with what one would expect based on the increase in atmospheric CO2 over that period.
So, is it possible that the current slowdown/pause could persist until 2030? Well, the energy imbalance in 1998 was probably around 0.6 Wm-2. If we follow a BAU emission scenario, atmospheric CO2 could increase to around 450ppm by 2030. Using ΔF = 5.35 ln (C/Co) would suggest that anthropogenic forcings would increase by about 1 Wm-2 if a surface temperature standstill also persisted until 2030. So, we’d have an energy imbalance of between 1.5 and 2 Wm-2 and the oceans would be absorbing significantly more energy than they are today. I guess it’s possible, but it seems somewhat unlikely. The oceans would need to absorb an ever increasing fraction of the excess energy.
So, the basic idea seems plausible, but even from the article itself it appears that it’s not accepted by all. However, it would seem unlikely that one could maintain the current conditions for much longer unless the planet is able to have a significantly higher energy imbalance than today without driving faster surface warming. I’ve written this quite quickly, so there’s probably much more that could be said and there may be some things I’ve missed, or mis-interpreted. The article itself, however, ends with
At present, strong tropical trade winds are pushing ever more warm water westward towards Indonesia, fuelling storms such as November’s Typhoon Haiyan, and nudging up sea levels in the western Pacific; they are now roughly 20 centimetres higher than those in the eastern Pacific. Sooner or later, the trend will inevitably reverse. “You can’t keep piling up warm water in the western Pacific,” Trenberth says. “At some point, the water will get so high that it just sloshes back.” And when that happens, if scientists are on the right track, the missing heat will reappear and temperatures will spike once again.