In a joint press conference NOAA and NASA have just released data for the global surface temperature for 2013. In summary they both show that the ‘pause’ in global surface temperature that began in 1997, according to some estimates, continues.
Statistically speaking there has been no significant trend in global temperatures over this period. All these years fall within the error bars of 0.1 deg C. The trend is less than this and is statistically insignificant. There is no statistical case for representing the post-1997 data as anything other than a constant line. The graphs presented at the press conference omitted those error bars.
When asked for an explanation for the ‘pause’ by reporters Dr Gavin Schmidt of NASA and Dr Thomas Karl of NOAA spoke of contributions from volcanoes, pollution, a quiet Sun and natural variability. In other words, they don’t know.
NASA has a temperature anomaly of 0.61 deg C above the average of 14.0 (1951 – 80) making it the 7th warmest year. Note that it is identical to 2003 and only 0.01 above 2009 and 2006. Taking into account the errors there has been no change since last year.
NOAA also has 2013 as the 4th warmest year, at 0.62 deg C above the global 20th century average of 13.9 deg C. Note that only 0.09 deg C separates their top ten warmest years. Each year has an associated error of 0.1 deg.
Courtesy NOAA. Click on image to enlarge.
Given that the IPCC estimates that the average decadal increase in global surface temperature is 0.2 deg C, the world is now 0.3 deg C cooler than it should have been.