UK Met Office Decadal Forecasts

[Jim Hunt]

The January 2017 Met Office decadal forecast has been published. See:

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/long-range/decadal-fc

and:

http://www.metoffice.gov.uk/research/news/decadal-forecasting

Despite the "decadal" in the title the UKMO forecast is actually for 2021, and is summarised thus:

Averaged over the five-year period 2017-2021, forecast patterns suggest enhanced warming over land, and at high northern latitudes. There is some indication of continued cool conditions in the Pacific sector of the Southern Ocean and enhanced warming in the Atlantic sector of the Southern Ocean. Current relatively cool conditions in the North Atlantic sub-polar gyre are predicted to return to more normal conditions with potentially important climate impacts over Europe, America and Africa.

During the five-year period 2017-2021, global average temperature is expected to remain high and is likely to be between 0.42°C and 0.89°C above the long-term (1981-2010) average. This compares with an anomaly of +0.46 ± 0.1 °C observed in 2016 (provisional), which makes 2016 one of the warmest two years on record. These high global temperatures are consistent with continued high levels of greenhouse gases and big changes that are currently underway in the climate system as highlighted in a recent Met Office research news article.

[jai mitchell]

I made this in Nov '16 it has obvious conservatisms within the general maintaining of the last 10-year warming trendline through 2035.   For example, a much more rapid removal of aerosols leading to further increased arctic warming producing rapid carbon cycle emissions from (once) frozen soils and a regional increase in albedo forcing which (by 2036) will be equal to approximately 1 watt per meter squared forcing (global average increase) but completely attributed to the arctic ocean.

[Jim Hunt]

A somewhat belated report on this year's UK Met Office decadal forecast.

The forecast is for continued global warming largely driven by continued high levels of greenhouse gases. However, other changes in the climate system, including a moderate La Niña in 2018 and longer term shifts in both the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), are also contributing. Near record temperatures are predicted during the coming five years, although La Niña is expected to cool 2018 slightly, consistent with the Met Office 2018 global mean temperature forecast. 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 negative PDO or negative AMO conditions which could temporarily cool climate, ten year global average warming rates are likely to be similar to late 20th century levels over the next few years. The recent slowdown in surface warming now appears to be at an end following a run of very warm years since 2014. For further discussion on the surface warming slowdown see the Met Office reports on the recent pause in warming and on the recent resumption of high warming rates.

The current forecast in graphical format, plus a look at how well the UKMO's 2012 forecast fared: