Thursday, February 05, 2015

Met Office prediction bias continues - just

Annually this blog monitors the Met Office prediction of global mean temperature for the year ahead and compares it with the outcome.  The striking observation is that almost without fail, the Met Office prediction is higher than the temperature turns out to be.  Now you would expect the prediction sometimes to overshoot and sometimes undershoot..  This trend seems to amount to a prediction bias.

Last January I reported the Met Office prediction had overshot the eventual temperature outcome in 14 out of the previous 15 years.  So how close did the December 2013 prediction for 2014 come.

The answer is very close.  But the Met Office prediction was still on the top side of the global mean temperature though only by one hundredth of a degree.  Now that is well within the margin of error and not too much should be read into it on its own.  But, taken along with the trend in the previous 15 years, it does nothing to reassure us that the Met Office has stripped out the bias in its prediction.

So that is now 15 out of 16 years of the Met Office shooting too high.  Here are the figures for the last 16 years with the 2015 prediction added.

Year  Forecast   Actual
1999. . . 0.38. . .0.26
2000. . .0.41 . . .0.24
2001. . .0.47 . . .0.40
2002. . .0.47 . . .0.46
2003. . .0.55 . . .0.46
2004. . .0.50 . . .0.43
2005. . .0.51 . . .0.47
2006. . .0.45 . . .0.43
2007. . .0.54 . . .0.40
2008 . . 0.37 . . .0.31
2009. . .greater than 0.41. . . 0.44
2010. . .0.58 . . .0.50
2011. . .0.44 . . .0.35
2012. . .0.48 . . .0.45
2013. . .0.57 . . .0.49
2014. . .0.57 . . .0.56
2015. . .0.64 

You can find details of the Met Office 2015 prediction here. They have bumped up the predicted temperature for 2015 to a figure 0.08 C higher than the previous highest temperature result in the series.

And finally, it is always useful to check predictions against reality. Here is Vicky Pope of the Met Office in 2004.  You can see her get 2014 temperature wrong - along with a few other things.  (You can see the video at the foot of last year's post on this topic.)

“By 2014 we’re predicting it will be 0.3 degrees warmer than 2004, and just to put that into context the warming over the past century and a half has only been 0.7 degrees, globally, there have been bigger changes locally but globally the warming is 0.7 degrees. So 0.3 degrees over the next ten years is pretty significant. And half the years after 2009 are predicted to be hotter than 1998 which was the previous record. So these are very strong statements about what will happen over the next ten years, so again I think this illustrates we can already see signs of climate change but over the next ten years we are expecting to see quite significant changes occurring.”

So Vicky's prediction of temperature increase was too high by a factor of almost three.  And Vicky was also wrong about 'half the years after 2009 being hotter than 2008'.

NB amended 170615 to show 2015 prediction 0.08 C above previous highest temperature result - rather than 0.8 C


3 comments:

  1. Look at it the other way Cameron: the prediction was an increase from 0.38 to 0.57 between 1999 and 2014. The actual result was an increase from 0.26 to 0.56 in the same time period, which was a faster rate of increase than predicted. We will need to wait and see what happens, but the overall upwards trend is quite clear. There are not many people who deny this now.

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