Ten years of 'accelerated global warming' ?

Data doesn’t support Obama’s claim

Guest essay by Christopher Monckton of Brenchley

During the July 2013 U.S. Senate hearing at which Roger Pielke Jr. and Roy Spencer gave stellar testimony to the visible discomfiture of the climate-extremist witnesses, none of the “Democrat” Senators and none of the people they had chosen to testify before them was at all anxious to defend Mr. Obama’s assertion that over the past decade global warming has been accelerating at an unforeseen rate.

At a fund-raiser for the “Democratic” Congressional Campaign Committee in Chicago May 29, he had said, “We … know that the climate is warming faster than anybody anticipated five or ten years ago.” He had added, “I don’t have much patience for people who deny climate change.”

Well, I deny that the climate is warming faster than anybody anticipated five or ten years ago. But I deny it not because I take an aprioristic position opposite to Mr Obama’s aprioristic position, but because science is done by measurement, not by parroting the Party Line. And the measurements do not support the Party Line.

Let me demonstrate. First, what warming does the IPCC anticipate in its upcoming and much-leaked Fifth Assessment Report?

The graph above, adapted from Figs. 11.33ab in the draft report, for which I am an expert reviewer, shows that from 2005-2050 (most of the past ten years fall within that period) the models expect an approximately linear warming of about 0.4 to 1.0 Cº per 30 years (this range is also explicitly stated in paragraph 11.3.6.3). That is equivalent to 1.33 to 3.33 Cº/century, with a mid-range estimate of 2.33 Cº/century.

The IPCC’s models’ mid-range projection implies that around 0.12 Cº of warming should happen over five years, and o.23 Cº over ten years. An eighth to a quarter of a Celsius degree: those are the benchmarks. Previous IPCC reports made broadly similar near-term projections.

What, then, is the consensus among the monthly global mean surface or lower-troposphere datasets about whether the climate is warming “faster than anybody anticipated five or ten years ago”? Or whether it is warming at all?

There are three terrestrial datasets: HadCRUt4, GISS, and NCDC. There are two satellite datasets: RSS and UAH. To forestall the usual futile allegations of cherry-picking, we shall look at all five of them.

For each dataset, two graphs will be displayed: the most recent 60 months of global temperature anomalies, and the most recent 120 months.

The graph will display the spline-curve of the monthly anomalies in dark blue, with a thicker light-blue trend-line, which is simply the least-squares linear-regression trend on the data. Over short periods, no more complex trend need be determined.

Nor is there any need to allow for seasonality, not only because the graphs analyze data over multiples of 12 months but also because globally the seasons cancel each other out, so that natural variability tends to make any seasonal pattern near-impossible to detect.

Linear regression determines the underlying trend in a dataset over a given period as the slope of the unique straight line through the data that minimizes the sum of the squares of the absolute differences or “residuals” between the data-points corresponding to each time interval in the data and on the trend-line.

The graphs, therefore, give a fair indication of whether global mean temperatures at or near the surface have been rising or falling over the past five or ten years.

Note, however, that – particularly with highly volatile datasets such as the global temperature anomalies – a statistical trend is not a tool for prediction. It indicates only what has happened, not what may or will happen.

And what has happened is, as we shall see, grievously at odds with the Party Line.

We begin with the terrestrial datasets.

GISS, five years:

GISS, ten years:

HadCRUT4, five years:

HadCRUt4, ten years:

NCDC, five years:

NCDC, ten years:

The mean of the anomalies on all three terrestrial datasets, five years:

The mean of the anomalies on all three terrestrial datasets, ten years:

Now for the two satellite datasets. RSS, five years:

RSS, ten years:

UAH, five years:

UAH, ten years:

The mean of the anomalies on the two satellite datasets, five years:

The mean of the anomalies on the two satellite datasets, ten years:

The mean of the anomalies on all five datasets, five years:

The mean of the anomalies on all five datasets, ten years:

The only dataset that shows any warming at all is UAH over ten years. The warming is a not particularly dizzying one twenty-fifth of a Celsius degree over ten years, equivalent to two-fifths of a degree per century.

The RSS satellite dataset, on the other hand, now shows no global warming at all for an impressive 199 months, or 16 years 7 months:

Not much “acceleration” there. Will it reach 200 months? I’ll report next month.

Finally, here is the monthly Global Warming Prediction Index, which compares the projections backcast by the modelers to 2005 and published in the IPCC’s Fifth Assessment Report with the real-world outturn as measured by the two satellite datasets.

The lower bound of the orange zone is the IPCC’s low-end projection. Warming should be occurring at a minimum of 1.33 Cº/century. The thick bright red line is the IPCC’s mid-range projection: warming should be occurring at 2.33 Cº/century.

The real-world trend, represented by the thick bright blue trend line, shows global temperatures declining since January 2005 at a rate equivalent to almost a quarter of a Celsius degree (half a Fahrenheit degree) per century.

You may think that going to the trouble of producing so many graphs is overkill. Yet when I first spoke up at the U.N. climate conference in Doha and pointed out that there had been no global warming for 16 years the delegates were furious. So were the news media. One reason for their unreason: they simply did not know the facts.

One would have thought that among all the hours of hand-wringing on the air and pages of moaning in print about “global warming”, most of the news media would be faithfully reporting the monthly temperature anomalies. But no. The facts do not fit the Party Line, so they are not reported. They are consigned to the Memory Hole.

As for Mr. Obama’s statement about “acceleration”, he was plain wrong. Instead of the warming equivalent to 2.33 Cº/century global warming that had been “anticipated”, there has really been no change in global temperature at all over the past five or ten years.

Will somebody tell the “President”?