There was a recent paper looking at the near term acceleration in the rate of temperature change. The Guardian covered it in an article called global warming set to speed up to rates not seen for 1000 years, while Carbon brief has a slightly more nuanced Earth entering a new era of rapid temperature change, study warms.
The paper basically used results from climate models to determine how multi-decade rates of change would vary in the future under various emission pathways. The figure on the right shows the results for RCP4.5 and indicates that, globally, the 40-year trend by 2020 could be around 0.25 ± 0.05oC per decade. It also shows the trends for different regions, although quite why it doesn’t show Africa is a little confusing since it seems to show all the other regions. Richard Betts, however, has a Climate Lab Book post where he points out that this study didn’t take into account that recent warming has been slower than the longer-term trend. Richard concludes that it is more likely that by 2020, the 40-year trend would be between 0.14 and 0.18oC per decade.
I initially thought that Richard’s result was on the low side, but I suspect he’s about right. In 2020, the 40-year trend will be based on the period 1980-2020. If you use the Skeptical Science Trend calculator and choose the dataset that will give your the highest trend from 1980-now (HadCRUT4-hydbrid), you get a trend of 0.176 ± 0.048oC per decade. For the 40-year trend in 2020 to be 0.18oC per decade would (if I’ve done this right) require about 0.1oC of warming between now and 2020. Even that would be more than twice as fast as we’ve been warming over the last 10-15 years. No warming at all would give a trend of 0.15oC per decade. To get to 0.2oC per decade would require almost 0.2oC of warming between now and 2020, and 0.25oC per decade would require almost 0.4oC of warming in the next 5 years.
So, it seems quite unlikely that we could have enough warming in the next 5 years for the 40-year trend to exceed 0.2oC per decade. It’s possible, I guess, but seems unlikely. To be clear, though, if we continue to increase our emissions, warming will have to accelerate at some stage: we can’t continue to build up an ever increasing planetary energy imbalance without this happening eventually. The current slowdown will probably simply delay when we reach the higher trends suggested by Smith et al. (2015) – assuming, of course, that we continue to follow a high-emission pathway. Of course, I suspect that this is one of those papers that we’ll never hear the end of if/when the 40-year warming trend doesn’t exceed 0.2oC per decade by 2020. That numerous people have pointed out that it might be unlikely to reach those levels quite as soon as 2020, won’t stop the whiners from saying “but you said…..”.