Last week the UK Meteorological Office issued its annual forecast for the global average temperature for the year ahead. They’re expecting a warm year, but very few people seemed to notice just how hot. Here’s what the press release had to say:
2013 is expected to be between 0.43 °C and 0.71 °C warmer than the long-term (1961-1990) global average of 14.0 °C, with a best estimate of around 0.57 °C, according to the Met Office annual global temperature forecast.
Taking into account the range of uncertainty in the forecast and observations, it is very likely that 2013 will be one of the warmest ten years in the record which goes back to 1850, and it is likely to be warmer than 2012.
Most press coverage ran with the “one of the warmest years” line, a simple elaboration of the press release, but few noticed that the Met Office were actually predicting a new global temperature record — perhaps because the Met Office wasn’t exactly trumpeting the fact from the rooftops. Admirable caution, you might say.
The Met Office “best estimate” for 2013 is that global average temperature will be 0.57ºC above the long term average (1961-1990), and that’s a comfortable 0.03ºC above the previous record years of 2005 and 2010. Take a look at the graph above. I’ve plotted global temperatures from 1993 to 2012 (data here), and added a line showing the linear trend over that period. The Met Office’s projection is just above an extension of the trend line. The grey “whiskers” on 2012 and 2013 show the full range covered by the projections. 2012 came in 0.03ºC below the December 2011 forecast.
2012 will end up as the ninth warmest year in the long term record, mainly because the year started out with a strong La Niña (which has a cooling effect on global temperature, with a six to nine month lag), and the El Niño (warming effect) which seemed to be on the way in mid year has all but fizzled out. Nevertheless, 2013 will start without a La Nina, and unless a strong one develops early in the year, the Met Office are clearly expecting that the long term warming trend will exert itself.
It’s a bold forecast — but one that’s in line with the warming of the last 20 years. Carbon dioxide continues to accumulate in the atmosphere, and energy continues to pile up in the climate system. New high temperature records are inevitable and unavoidable until the climate gets back into energy balance, and that isn’t going to happen any time soon ((30 years is the usual period estimated to allow the upper layers of the ocean to “catch up” with warming)). We ain’t seen nothing yet, and that’s not good news.