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Standstill, What Standstill?

Dr David Whitehouse

The World Meteorological Organisation (WMO) has released its assessment of the global surface temperature for 2013. It calculates its own global temperature based on HadCRUT4, NOAA and NASA. Unsurprisingly it shows that 2013 tied with 2007 as the sixth warmest year with a temperature anomaly of 0.50 deg C above the 1961 – 90 average.

“The global temperature for the year 2013 is consistent with the long term warming trend,” said WMO Secretary-General Michel Jarraud. “The rate of warming is not uniform but the underlying trend is undeniable. Given the record amounts of greenhouse gases in our atmosphere, global temperatures will continue to rise for generations to come,” said Mr Jarraud.

The WMO figure quoted by the UK Met Office a week before the WMO officially released it was 0.5 +/- 0.1, which as I noted at the time is the best expression of the global temperature given the +/- 0.1 deg C uncertainty. So I wondered, why not stick to the scientific practice we tell students to follow concerning measurements and errors and plot the WMO’s data with this level of accuracy and precision.

As usual I have started in 1997 for the reasons often mentioned before, i.e. going back through the data from the present day the last data point that satisfies the no trend hypothesis is 1997. Using an exaggerated temperature scale it looks like this. Click on the image to enlarge.

WMO Fig 1

The variations are statistically unimportant. This is thought provoking since the measurements include slight rises and falls due to El Nino’s and La Nina’s. But the data looks even more striking when plotted like this. Click on image to enlarge.

WMO Fig2

This brings out just how constant the global surface temperature has been when the data is treated according to scientific best practice. Can you see the “standstill?”

According to the WMO Secretary-General Michel Jarraud the rate of warming is not uniform, which is true, and that the underlying trend is undeniable, which depends upon how you look at the data.

Torture the data and it will confess to anything, or so it is said, and there are some who not only torture the data but do so with a particular confession in mind. A recent analysis of the post 1979 global surface temperature is a good example of this.

In it the analyst takes HadCRUT4 data from 1979 to 1997 and uses the trend calculated from it to predict what would have happened over the past 16 years if the warming had continued or had stopped. Although in this analysis there is a problem with the sensitivity of the final value of the regression line to the last data points chosen and the incorrect temperature chosen for the “standstill” that taken together yields the admission the analyst desires, it is an interesting question to pose. Looking at the post-1997 data is there any statistical evidence that it is part of the warming trend established in the earlier part of the post-1979 data?

The answer is no, as is obvious from its lack of trend and its low scatter around a constant temperature. It is not a case, as Michel Jarraud says of,” the rate of warming is not uniform but the underlying trend is undeniable.” If one looks at the 1979 -2013 data then one can obviously draw a straight warming line through all the data. But something happened around 1997-98 that rendered the two sections of the data statistically independent.

“There’s No Warming Standstill.”

The Climate News Network carried a story on the WMO figures producing what was essentially a regurgitated WMO press release plus one extra quote from Michel Jarraud.

Extract: Asked by Climate News Network how WMO regarded claims by some critics that there has been a “global warming standstill since 1997″, Mr Jarraud said: “Which standstill? The coldest year since 2001 is warmer than any year before 1998…“Each decade is warmer than the previous one. There is global variability from year to year. You have to look at the longer period. If you do that, then the message is beyond any doubt…despite the fact that there was no El Niño in 2013, it was still the sixth warmest year. This is significant.”

The Climate News Network should have checked because according to WMO’s own data the first quote is incorrect, as the graph shows. Also it would have been better journalism to include a scientist who thinks the “standstill” is a real, though unexplained, event. There are now lots of them, probably a majority.