Guest essay by Eric Worrall
h/t The Express – The British MET have forecast that large areas of the world will cool over the next 5 years, though they still expect global average temperatures to remain high. Of course, they also still claim that CO2 is in the driving seat.
Spatial patterns suggest enhanced warming over land and at high northern latitudes. There is some indication of continued cool conditions in the Southern Ocean, and of relatively cool conditions in the North Atlantic sub-polar gyre. Uncertainties in the forecast are considerable: for the period 2016-2020 most regions are expected to be warmer than the average of 1981 to 2010, but regional cooling is possible over much of the Southern Ocean and the North Atlantic sub-polar gyre. Differences with our forecast issued last year are expected because the updated forecast has been made with an upgraded version of our model. Nevertheless, both forecasts suggest relatively cool conditions in the Southern Ocean and the North Atlantic sub-polar gyre although the magnitude of the anomalies is smaller in the updated forecast. Further forecasts from other international modelling centres are available from the multi-model decadal forecast exchange.
During the five-year period 2016-2020, global average temperature (see blue shading in Figure 3 below) is expected to remain between 0.28°C and 0.77°C (90% confidence range) above the long-term 1981-2010 mean (0.88°C to 1.37°C relative to pre-industrial conditions represented by the period 1850 to 1900). The warmest individual year in the 160-year Met Office Hadley Centre global temperature record is 2015 with a temperature of 0.44 ± 0.1 °C above the 1981-2010 mean. Averaged over the whole five-year period 2016-2020, global average temperature is expected to be between 0.42°C and 0.67°C above the 1981-2010 mean (1.02°C to 1.27°C relative to pre-industrial conditions).
The forecast is for continued global warming largely driven by continued high levels of greenhouse gases. However, other changes in the climate system, including the largest El Niño since 1997 and longer term shifts in both the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), are also contributing. Near record temperatures are predicted for the coming five years, consistent with the Met Office annual global temperature forecast. However, the recent run of consecutive record years is likely to end in 2017 as El Niño declines. The forecast remains towards the mid to upper end of the range simulated by CMIP5 models that have not been initialised with observations (green shading in Figure 3). Barring a large volcanic eruption or a very sudden return to La Niña or negative AMO conditions which could temporarily cool climate, ten year global average warming rates are likely to return to late 20th century levels within the next two years. Nevertheless, the recent slowdown in surface warming is still an active research topic and trends over a longer (15 year) period will take longer to respond. For further discussion on the surface warming slowdown see the Met Office reports on the recent pause in warming and on big changes underway in the climate system.
The last paragraph is interesting. The MET don’t know what caused the pause. They acknowledge the cooling effects they have identified could be substantial enough to drag down global average temperatures. The MET still think CO2 is driving a dangerously rapid rise in global temperatures, they’re just not sure when the temperatures will actually rise.