Thursday, November 2, 2017

Global temperature continues to cool

Global temperature continues to cool

 / 18 hours ago November 1, 2017
Global effects of El Niño event seem to have passed, and we’ve cooled to a value just before the event, according to data from the UK Hadley Climate Centre
Earlier we reported on ocean temperatures dropping, now we have confirmation that global air temperature is dropping as well. The latest data is in, and now according to HadCRUT data, we are back to the same level as before the 2014/2016 super El Niño event heated up the planet.
Clive Best writes:
The HadCRUT4.5 temperature anomaly for September calculated by spherical triangulation is 0.54C, a fall of 0.17C since August. Temperatures have seemingly returned to a long trend after the 2016 El Niño.
Monthly temperature anomalies for HadCRUT4.5 (HadSST3 and CRUTEM4.6 stations data) calculated by spherical triangulation method. Click for a larger image
Clive Best uses a custom triangulation method to calculate the global temperature anomalyfrom the raw data, so I thought I’d verify this from the publicly available HadCrut data.
HadCRUT4 time series
These ‘best estimate’ series are computed as the medians of regional time series computed for each of the 100 ensemble member realisations. Time series are presented as temperature anomalies (deg C) relative to 1961-1990.
Quoted uncertainties are computed by integrating across the distribution described by the 100 ensemble members, together with additional measurement and sampling error and coverage uncertainty information.
The data files contain 12 columns:
  • Column 1 is the date.
  • Column 2 is the median of the 100 ensemble member time series.
  • Columns 3 and 4 are the lower and upper bounds of the 95% confidence interval of bias uncertainty computed from the 100 member ensemble.
  • Columns 5 and 6 are the lower and upper bounds of the 95% confidence interval of measurement and sampling uncertainties around the ensemble median. These are the combination of fully uncorrelated measurement and sampling uncertainties and partially correlated uncertainties described by the HadCRUT4 error covariance matrices.
  • Columns 7 and 8 are the lower and upper bounds of the 95% confidence interval of coverage uncertainties around the ensemble median.
  • Columns 9 and 10 are the lower and upper bounds of the 95% confidence interval of the combination of measurement and sampling and bias uncertainties.
  • Columns 11 and 12 are the lower and upper bounds of the 95% confidence interval of the combined effects of all the uncertainties described in the HadCRUT4 error model (measurement and sampling, bias and coverage uncertainties).
More details are given in the paper introducing the dataset.
According to the Japanese Meteorological Agency, the 2014-2016 El Niño event formed in May 2014.
Plotting the HadCRUT4.5 data (column 2, mean anomaly) for that period yields this:
Plot of global temperature anomaly from HadCRUT4.5 data from January 1999 to September 2017. Note values for May 2014 compared to September 2017. Click image to enlarge.
In May 2014, at the beginning of the ENSO event, Global Temperature Anomaly was 0.608, now in September 2017, it has cooled to 0.561. It appears all affects from that ENSO event are now removed from the global temperature record.
Looks like claims of the “hottest year ever” won’t be happening in 2017, and we may see a return of “the pause” soon.


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