Clearly, David Whitehouse has enough rope. To hang himself.

The WUWT blog has a post by David Whitehouse (of the “Global Warming Policy Foundation”) discussing global temperature data. It features this graph from the leaked copy of the not-yet-completed 5th assessment report (AR5) of the IPCC (Intergovernmental Panel on Climate Change):





What’s surprising is that Whitehouse spends so little effort discussing the graph itself. Instead, he chooses to paint a perversely false picture of global temperature change.

For one thing, Whitehouse is indignant about a comparison of the global temperature trend over the last 50 years to that over the last 100 years. As Whitehouse says:



In Chapter 2 the report says that the AR4 report in 2007 said that the rate of change global temperature in the most recent 50 years is double that of the past 100 years. This is not true and is an example of blatant cherry-picking. Why choose the past 100 and the past 50 years? If you go back to the start of the instrumental era of global temperature measurements, about 1880 (the accuracy of the data is not as good as later years but there is no reason to dismiss it as AR5 does) then of the 0.8 – 0.9 deg C warming seen since then 0.5 deg C of it, i.e. most, occurred prior to 1940 when anthropogenic effects were minimal (according to the IPCC AR4).



Why choose 50 and 100 years? Because they’re nice round numbers, that’s why. They also make the point — the temperature trend (estimated by linear regression) really is twice as fast over the last 50 years as it was over the last 100 years.

What’s actually not true is Whitehouse’s claim that “of the 0.8 – 0.9 deg C warming seen since then 0.5 deg C of it, i.e. most, occurred prior to 1940.” It takes some real cherry-picking to do that.

The claim that “most of the warming occurred prior to 1940” actually originated, as far as I know, in the mendacious “documentary” The Great Global Warming Swindle by Martin Durkin. To support that claim, Durkin simply faked the data.

Whitehouse just makes the claim, as if asserting it somehow makes it true. Let’s look at some actual data, from NASA. The only way to get 0.5 deg.C warming prior to 1940 is to take the difference between the lowest annual average and the highest annual average during that time period:

Taking the difference between the lowest and highest annual averages includes the noise of year-to-year fluctuations, which makes it a false representation of the actual global warming which took place.

You wanna play that game? OK. Let’s take the difference between the lowest and highest annual averages after 1940. That gives a post-1940 warming of 0.85 deg.C.

That puts the lie to Whitehouse’s claim that “most occurred prior to 1940.” But then, using the range-of-annual-averages method gives a total warming of 1.06 deg.C — Whitehouse’s fake 0.5 isn’t even half of that, let alone “most.”

A better characterization of the net warming is to use the extreme values of a smoothed estimate of global temperature:

That puts the pre-1940 warming at 0.34 deg.C and the post-1940 warming at 0.64 deg.C, with a total range of 0.93 deg.C. Again, the pre-1940 warming isn’t even half, certainly not “most.”

If you insist on partitioning the warming between pre- and post-1940 so the two values add up to the total, a fair estimate gives 0.32 deg.C before and 0.61 deg.C after:

Any way you slice it honestly, the pre-1940 warming is not “most” of the total. It’s not even half. It’s more like a third. David Whitehouse’s characterization is a fake.

As for more recent temperature change, Whitehouse’s viewpoint is perhaps best summed up by this statement of his:



So since 1979 we have has [sic] about 16 years of warming and 16 years of temperature standstill.



Really?

First, Whitehouse is pulling an old favorite trick of fake skeptics: equating the lack of statistically significant warming with the lack of warming. If we look at global surface temperature according to the three main data sets (GISS, HadCRUT4, and NCDC), all three show warming over the last 16 years (2012 still has one month to go, but the difference won’t amount to a hill of beans):

Although all three trend lines slope upward, their slopes aren’t statistically significant. But that doesn’t mean they’re not upward. It just means that there’s not enough data in 16 years to tell for sure, statistically speaking, which way they’re going. That always happens — always — when the time span is short.

That’s why fake skeptics like David Whitehouse like to focus on short time spans.

Whitehouse declares that we’ve had “about 16 years of warming and 16 years of temperature standstill.” According to Whitehouse, all the global warming earth has experienced recently was complete by 16 years ago (the end of 1996). Is that really so? Let’s take a closer look at the last 16 years, compared to what happened before that, starting in 1979 (Whitehouse’s choice).

I’ll do a similar exercise to one I’ve done before. I’ll take the data from 1979 (Whitehouse’s starting point) up to 16 years ago (less one month, the end of 1996). Then I’ll fit a trend line with least-squares regression. Then I’ll extend that trend line to the present, to see what would have happened if that trend continued.

If David Whitehouse is giving an honest portrayal of global temperature, then most of the data points from 1997 onward should be below the extended trend line, since the trend will keep rising but according to him, global warming stopped back then.

If we do this exercise using data from NASA GISS, we get this:

Let’s try using the HadCRUT4 data set instead:

Once more into the fray: let’s try using the NCDC data set instead:

Well well … Plainly, it is not the case that most of the data points from 1997 onward are below the extended trend line. As a matter of fact, for all three data sets, every year from 1997 onward has been hotter than expected according to that trend from 1979. There’s only one valid conclusion: David Whitehouse gave a fake portrayal of global temperature.

Thats what fake skeptics do.

What about the plot from the draft of the AR5 report? It compares projections based on multi-model averages from FAR (first assessment report), SAR (second assessment report), TAR (third assessment report) and AR4 (fourth assessment report) to observations (annual averages) from NASA GISS, HadCRUT4, and NCDC. In my opinion, there is a flaw in how the comparison is done. I don’t suspect it’s an intentional mistake, but I do believe it’s a mistake.

The flaw is this: all the series (both projections and observations) are aligned at 1990. But observations include random year-to-year fluctuations, whereas the projections do not because the average of multiple models averages those out. Using a single-year baseline (1990) offsets all subsequent years by the fluctuation of that baseline year. Instead, the projections should be aligned to the value due to the existing trend in observations at 1990.

Aligning the projections with a single extra-hot year makes the projections seem too hot, so observations are too cool by comparison. This is indeed a mistake — it would be just as much a mistake to align the projections with a single extra-cool year (like 1992), which would make the projections too cool and observations too hot by comparison.

We can estimate the observational fluctuation that by fitting a smoothed curve to the observed data to estimate a nonlinear trend, and noting the difference between the 1990 value and the smoothed value. Doing so indicates that GISS and HadCRUT4 are both about 0.12 deg.C hotter than the existing trend, while NCDC is about 0.10 deg.C hotter.

Fortunately, the draft version of the AR5 report gives the actual data used to plot the projections for FAR, SAR, and TAR (but not for AR4). So, we can make our own version of the comparison. Here’s the comparison as presently done in the report, with all observed series aligned to projections in 1990:

What should be done is to offset the observations so that the hotter-than-average 1990 really is hotter than average. When I offset the observations by 0.1 deg.C, we get more realistic comparison of observations to projections:

It turns out that observed global temperature has gone “right down the middle” of the IPCC projections. But, fake skeptics want you to believe otherwise. That’s what fake skeptics do.

There’s another way we can compare projections to observations from 1990 to the present; we can compute the trend estimated by linear regression. When we do that, we get this:

Once again, observed global temperature has gone “right down the middle” of the IPCC projections.

Yet fake skeptics like David Whitehouse are trying their best to spin the AR5 report (which isn’t even published yet) in order to discredit global warming science. David Whitehouse also chose to paint a picture of global temperature which is as fake as can be.

That’s what fake skeptics do.