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Tuesday, November 6, 2018

No discernible change points in WUWT temperature conspiracies

Sou | 4:26 AM Go to the first of 4 comments. Add a comment
The hogwash from science deniers continues, this time with a rather silly claim by Bob Tisdale. He doesn't accept the maths behind the use of anomalies in science, and reckons the reason anomalies are used to illustrate changes in global temperature is to hide seasonal differences throughout the year, or between land and oceans, or some such nonsense.

Bob Tisdale is what at best could be termed a pseudo-scientist. He specialises in rejecting climate change science, usually using very poor and unscientific graphs to get his audience to clap. And he chooses to publish on denier blogs where the audience will clap anything, as long as it's one of climate science is a hoax, the world is cooling, it can't be happening, Trump is the best, and all the scientists in the world are wrong, or stupid, or similar.

Today he's "supported" his silliness by putting up some charts, which he says he based on data from Berkeley Earth and NOAA's sea surface temperature, ERSST v5. He seems very surprised to find that the hottest months globally are July and August.

With a bit of reflection he might have understood why that is so. As is usual for Bob, he didn't manage to get that far, even though it was stated in his source:
As Earth's land is not distributed symmetrically about the equator, there exists a mean seasonality to the global land-average.
(The main reason the northern hemisphere dominates global temperature - warm in the NH summer and cold in the NH winter - is because there is more land surface in the northern hemisphere. Land heats up and cools down much more quickly than the sea does.)



While Bob didn't get to point this out, he did manage to find an estimate of monthly absolute temperatures at Berkeley Earth. I've copied this below, less the confidence limits (from +/- 0.11 to +/- 0.13). The range is just under 12°C, with January the coldest month and July the hottest (usually, not always).

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
2.59
3.21
5.31
8.32
11.33
13.47
14.34
13.87
12.09
9.25
6.09
3.62
Table 1 | Estimated Jan 1951-Dec 1980 monthly absolute temperature for land only. Source:Berkeley Earth.


The above can be compared with the estimate made by Phil Jones back in 1999, which was for land and sea combined. He wrote:
The climatology indicates that the annual average surface temperature of the world is 14.0°C (14.6°C in the Northern Hemisphere (NH) and 13.4°C for the Southern Hemisphere). The annual cycle of global mean temperatures follows that of the land‐dominated NH, with a maximum in July of 15.9°C and a minimum in January of 12.2°C.

Hiding the incline

Back to Bob and his silly (and wrong) graphs. What he did, can you believe, was apply a linear trend line to temperature data from 1850 right up to the present. He ignored the changing trends over that period. Imagine measuring the height of a person as a baby (say, 50 cm), and then measuring the height of that person when they were 95 years old (say, 185 cm), and saying they must have grown at a rate of 1.42 cm a year! Well, that's effectively what Bob Tisdale did.

Compare these charts. The first one shows the changing trend, using change points as calculated by Niamh Cahill, Stefan Rahmstorf and Andrew C Parnell, published in a paper a couple of years ago.

Figure 1 | Global temperature trend changes over time. The data change points are as calculated in Cahill15. Temperature anomaly data source: NASA GISTemp.

The above chart highlights the different trends recorded over time. First there was a cold spell, up until around 1920. Then it got warm fairly quickly (although some of that warming in the 1940s could still be a bit suspect). Then there was a a bit of cooling, or at least after the temperature dropped from the high in the early 1940s there wasn't an increase. Then the temperature took off and the world has been heating up very quickly since the early 1970s.

Compare all the information you can glean from the above chart with the chart Bob Tisdale put up (it doesn't show on the archived page, but you can see it here). The annotations are mine!


What is he trying to say? Well, he seems to have summed it up in his closing comments:
[Sarc on.] Hmmmm, maybe the doomsters do know, and the examples above in Figures 3 and 4 are the real reasons why NASA GISS, NOAA NCEI, and the Met Office’s Hadley Centre will only furnish their global land-plus-ocean surface temperature data and global land-air surface temperature data in anomaly form. Oops, it appears that NASA GISS, NOAA NCEI, and the Met Office’s Hadley Centre forgot to tell Berkeley Earth, and Berkeley Earth spoiled it for them all. Oh well, back to the old drawing board! [Sarc off.]

Well, know, Bob. That's not the reason.


How are anomalies calculated or why aren't absolute temperatures used?

Absolute temperatures aren't used because to do so is too difficult (and distracting). Although the different research teams use different ways of working out global temperature changes, they all require getting data from heaps of individual measurements at different heights, in different locations and, often, taken at different times of the day. Many teams then apply a grid to the planet surface and work out how the temperature has changed over each grid "square". Then they compile all the changes (anomalies) to work out how the temperature over all the earth's surface has changed. Hansen10 has a good explanation of what is done at NASA GISS.

What is not done is to get all the raw temperature data from weather instruments and take a simple average and say that's the temperature of the world. That would give a very wrong picture of what is happening, and wouldn't just be meaningless it would be misleading. It would say worse than nothing about global temperature trends.

The Climatic Research Unit at the University of East Anglia provides this explanation:
Stations on land are at different elevations, and different countries measure average monthly temperatures using different methods and formulae. To avoid biases that could result from these problems, monthly average temperatures are reduced to anomalies from the period with best coverage (1961-90). For stations to be used, an estimate of the base period average must be calculated. Because many stations do not have complete records for the 1961-90 period several methods have been developed to estimate 1961-90 averages from neighbouring records or using other sources of data (see more discussion on this and related points in Jones et al., 2012). Over the oceans, where observations are generally made from mobile platforms, it is impossible to assemble long series of actual temperatures for fixed points. However it is possible to interpolate historical data to create spatially complete reference climatologies (averages for 1961-90) so that individual observations can be compared with a local normal for the given day of the year (more discussion in Kennedy et al., 2011).

It is possible to obtain an absolute temperature series for any area selected, using data from the absolute file, and then add this to a regional average of anomalies calculated from the gridded data. If for example a regional average is required, users should calculate a regional average time series in anomalies, then average the absolute file for the same region, and lastly add the average derived to each of the values in the time series. Do NOT add the absolute values to every grid box in each monthly field and then calculate large-scale averages.

From the WUWT comments


Nothing surprising in the comments. They tended to have a lot of "where I live the temperature can get from -8C to +90C therefore global warming doesn't matter" (except in Fahrenheit, mostly). I'll give you a couple of others, just to save you the trip :)

Lasse seems to think the Arctic has been paved over with tar and cement:
November 5, 2018 at 4:56 am
Less cool winter in Arctic and less cool nights.
That is the result of more water in the air and more asphalt on the ground.
It is like the sea. It gives heat distribution.
Phil Rae is a "very serious person" who is itching for the day the world discovers that climate science is a hoax:
November 5, 2018 at 5:20 am
Another informative post, Bob – thank you! However, we need this kind of information to be shouted from the mountain tops. We risk losing this fight if we don’t do something to counter the propaganda of the BBC, CNN & the vast majority of MSM broadcasters & newspapers, both print & online. Our schools are busy raising a generation of youngsters spoon-fed on catastrophist propaganda.
I realise that isn’t a revelation to most denizens of WUWT but we ignore it at our peril. We need to find better ways to put real information in the hands of those who will make decisions in the future…..and we need to find ways to stop governmental complicity in this scam across much of the free world.
Sparko doesn't believe Bob Tisdale when he uses Berkeley Earth data. He thinks that some nefarious person or other purged all information about the annual variation in surface temperature.
November 5, 2018 at 5:41 am
Hmmmn, all the information on annual variation in surface temperature got purged from the internet some years ago. Can’t have real facts out there, the people may stray from the reservation.

Seekerofthetruth makes a racist comment tinged with white supremacy notions, to which no-one appears to object.
November 5, 2018 at 6:19 am
No,Bob. You just don’t understand the problem. Hotter summers will be bad for good brown people in warm countries; less cold winters will be good for bad pale people in cold countries. Double plus ungood!

References and further reading


Niamh Cahill, Stefan Rahmstorf and Andrew C Parnell. "Change points of global temperature". 2015 Environ. Res. Lett. 10 084002. doi:10.1088/1748-9326/10/8/084002 (open access)

Jones, P. D., M. New, D. E. Parker, S. Martin, and I. G. Rigor (1999), "Surface air temperature and its changes over the past 150 years", Rev. Geophys., 37(2), 173–199, doi:10.1029/1999RG900002 (open access)

Hansen, James, Reto Ruedy, Mki Sato, and Ken Lo. "Global surface temperature change." Reviews of Geophysics 48, no. 4 (2010). (open access)




4 comments:

  1. From observation, the cardinal rule for climate change deniers when determining temperature trends is: never, ever, use a sensible time period.

    ReplyDelete
  2. The globe does not have an "absolute" temperature in that sense, it is kind of an abstract fiction. I know many of the climate scientists still use it, but I know from interviews that a couple are against it. But if a reporter asks "what is the temperature of the earth now", you have to give them something I guess.

    I just think of the "absolute" temperature as a baseline used to estimate any increase or decrease - to me it is like the stockmarket indices.

    ReplyDelete
  3. all this nonsense demonstrates is that if you really really try and mine the data hard enough you can get it to tell you whatever you want - great, now grow up and do something useful!!!

    ReplyDelete
  4. As witless a post as Tisdale has ever churned out.
    He has discovered the seasons, and the ocean: early human cognitive status will be his soon if he keeps up that sort of progress.
    Well done, Bob!

    ReplyDelete

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