Regular readers will recall that we recently sent The Telegraph a lesson or two about global surface temperature “adjustments”, both of which included “a video by a scientist who has studied such matters”. It seems nobody at The Telegraph, and particularly Christopher Booker, bothered to watch it or do the homework assignments. The stated view of Jess McAree, Head of Editorial Compliance at the Telegraph Media Group, is that:
Only the most egregious inaccuracy could be significantly misleading.
We therefore take great pleasure in welcoming Dr. Kevin Cowtan from the University of York, the “scientist” mentioned above, who has kindly allowed us to reprint an article of his originally published at Skeptical Science. Please read on below the fold, and don’t forget to do your homework!
There has been a vigorous discussion of weather station calibration adjustments in the media over the past few weeks. While these adjustments don’t have a big effect on the global temperature record, they are needed to obtain consistent local records from equipment which has changed over time. Despite this, the Telegraph has produced two highly misleading stories about the station adjustments, the second including the demonstrably false claim that they are responsible for the recent rapid warming of the Arctic.
In the following video I show why this claim is wrong. But more importantly, I demonstrate three tools to allow you to test claims like this for yourself.
The central error in the Telegraph story is the attribution of Arctic warming (and somehow sea ice loss) to weather station adjustments. This conclusion is based on a survey of two dozen weather stations. But you can of course demonstrate anything you want by cherry picking your data, in this case in the selection of stations. The solution to cherry picking is to look at all of the relevant data – in this case all of the station records in the Arctic and surrounding region. I downloaded both the raw and adjusted temperature records from NOAA, and took the difference to determine the adjustments which had been applied. Then I calculated the trend in the adjustment averaged over the stations in each grid cell on the globe, to determine whether the adjustments were increasing or decreasing the temperature trend. The results are shown for the last 50 and 100 years in the following two figures:
Trend in weather station adjustments over the period 1965-2014, averaged by grid cell. Warm colours show upwards adjustments over time, cold colour downwards. For cells with less than 50 years of data, the trend is over the available period.
Trend in weather station adjustments over the period 1915-2014, averaged by grid cell. Warm colours show upwards adjustments over time, cold colour downwards. For cells with less than 100 years of data, the trend is over the available period.
In the video I demonstrate three tools which are useful in understanding and evaluating temperature adjustments:
A GHCN (global historical climatology network) station report browser. GHCN provide graphical reports on the adjustments made to each station record, but you need to know the station ID to find them. I have created an interactive map to make this easier.
The majority of cells show no significant adjustment. The largest adjustments are in the high Arctic, but are downwards, i.e. they reduce the warming trend. This is the opposite of what is claimed in the Telegraph story. You can check these stations using the GHCN station browser.
The upward adjustments to the Iceland stations, referred to in the Telegraph, predate the late 20th century warming. They occur mostly in the 1960’s, so they only appear in the centennial map. Berkeley Earth show a rather different pattern of adjustments for these stations.
Iceland is a particularly difficult case, with a small network of stations on an island isolated from the larger continental networks. The location of Iceland with respect to the North Atlantic Drift, which carries warm water from the tropics towards the poles, may also contribute to the temperature series being mismatched with records from Greenland or Scotland. However given that the Iceland contribution is weighted according to land area in the global records, the impact of this uncertainty is minimal. Global warming is evaluated on the basis of the land-ocean temperature record; the impact of adjustments on recent warming is minimal, and on the whole record it is small compared to the total amount of warming. As Zeke Hausfather has noted, the land temperature adjustments in the early record are smaller than and in the opposite direction to the sea surface temperature adjustments.
Impact of the weather stations adjustments on the global land-ocean temperature record, calculated using the Skeptical Science temperature record calculator in ‘CRU’ mode.
Manual recalibration of the Iceland records may make an interesting citizen science project. Most of the stations show good agreement since 1970, however they diverge in the earlier record. The challenge is to work out the minimum number of adjustments required to bring them into agreement over the whole period. But the answer may not be unique, and noise and geographical differences may also cause problems. To facilitate this challenge, I’ve made annualized data available for the eight stations as a spreadsheet file.
In the video I demonstrate three tools which are useful in understanding and evaluating temperature adjustments:
- A GHCN (global historical climatology network) station report browser. GHCN provide graphical reports on the adjustments made to each station record, but you need to know the station ID to find them. I have created an interactive map to make this easier.
- The Berkeley Earth station browser. The Berkeley Earth station reports provide additional information to help you understand why particular adjustments have been made.
- The Skeptical Science temperature record calculator. This allows you to construct your own version of the temperature record, using either adjusted or unadjusted data for both the land and sea surface temperatures.
Data for the temperature calculator may be obtained from the following sources:
- The GHCN station data. For daily average temperature data, look for the ‘tavg’ files. The ‘qca’ files are adjusted temperatures, and the ‘qcu’ files are unadjusted temperatures. The files are stored in ‘.tar.gz’ archives, and may be extracted using most freely available unzip software.
- The Hadley sea surface temperature data. Look for the files HadSST.3.1.1.0.median.zip, or HadSST.3.1.1.0.unadjusted.zip for the unadjusted data.
Finally, here are some interesting papers discussing why adjustments are required.
- Menne et al (2009) The U.S. historical climatology network monthly temperature data, version 2.
- Bohm et al (2010) The early instrumental warm-bias: a solution for long central European temperature series 1760–2007.
- Brunet et al (2010) The minimization of the screen bias from ancient Western Mediterranean air temperature records: an exploratory statistical analysis.
- Ellis (1890) On the difference produced in the mean temperature derived from daily maximum and minimum readings, as depending on the time at which the thermometers are read
Finally, for the moment at least, and lapsing back into our by now familiar (and adversarial?) style:
Us:
@JessMcAree Is #Booker back at #School? http://t.co/J0UMqg5Fbx @LabradorIce @skepticscience @coxypm @ClimateExeter @theresphysics @ichiloe
— Snow White (@GreatWhiteCon) February 27, 2015
Them:
We’ll keep you posted!
Christopher Booker thinks NOAA is distorting global land temperature data to inflate reported global warming, and fan the flames of climate alarmism, and he’s written a couple of articles about it.
Dr. Kevin Cowtan contends Booker is wrong, and he created a couple of YouTube videos about it. Dr. Cowtan trusts that NOAA’s adjustments are justified and correct, and he also says they are too minor to be questionable. “Why would they do that?” he asks at the end of his first video, meaning why would anyone commit fraud for an inconsequential difference in the result?
I don’t know with certainty whether or not NOAA’s adjustments are all justified and correct, but I found Dr. Cowtan’s argument unpersuasive, for two reasons.
The first reason is that he assumes fraudulent intent is the only possible explanation for biased results, but it isn’t. If the results are biased to exaggerate warming, it could also be due to confirmation bias or other error, even by people with the best of intentions.
However, Dr. Cowtan’s argument also depends on the adjustments being inconsequential, and they are not. I digitized the endpoints of one of Dr. Cowtan’s graphs using WebPlotDigitizer and found that his own analysis proves NOAA’s adjustments are far from inconsequential. By comparing the adjusted and unadjusted versions of Dr. Cowtan’s graphs of globally averaged land surface air temperatures, I found that NOAA’s adjustments increased the reported warming by 35%.
35% is not inconsequential.
Details here:
http://tinyurl.com/cowtan-v-booker
Hello again Dave,
I note that you have been pursuing your enquiries over on the Skeptical Science web site. Quoting from Dr. Cowtan’s response to you there:
I arbitrarily took a quick look at Resolute using the Denial 101x temperature tool, to reveal this:
It looks to me as though the Canadian Arctic Archipelago is warming quite quickly at present. What do you think?
Hi Dave,
I don’t usually get involved in “debates” about global surface temperatures. However in this case Christopher Booker was quoting some of Paul Homewood’s nonsense about my beloved Arctic, so I did. Here’s the original story:
A Letter to the Editor of the Sunday Telegraph
You will note that the response I received from The Telegraph’s very own Head of Editorial Compliance stated that:
not to mention that:
In such circumstances might I enquire why you give any credence whatsoever to Mr. Booker’s opinions, on this or any other even vaguely scientific topic?
Hi Jim,
Your “beloved Arctic?” Do you love the Arctic more than the Antarctic? Why?
The global sea-ice trend since 1979 is zero, flat, neither significantly up nor significantly down. Global sea ice extent is essentially identical this year to what it was 35 years ago. Sure, if you cherry-pick one region or another, you can show a slight trend, either up or down, but the global trend is essentially flat:
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg
Paul Homewood is a mensch. He does not writes “nonsense.” The 1979 start date for commonly used sea-ice graphs is because the earliest data used cones from Nimbus-7, which launched in late 1978.
Missions prior to Nimbus-5, i.e., circa 1965 through 1972, did not have instruments which were capable of detecting sea ice through clouds. However, there used to be data from passive microwave satellite measurements of sea ice extent in the mid 1970s, made by Nimbus-5, Nimbus-6 and Seasat-1. Unfortunately, NASA has apparently lost much of that data.
Hi Dave,
Evidently my deadpan Anglo-Saxon humour eludes you?
Since you evidently frequent Skeptical Science I suggest you read the following carefully and then come back and try and talk some sense on Arctic sea ice extent, which is the topic under discussion here, just like it says at the top.
http://www.skepticalscience.com/arctic-antarctic-sea-ice.htm
Paul Homewood certainly writes nonsense about my beloved Arctic. Please answer my “Resolute” question above instead of heading off on a gish gallop around the denialosphere.
Thanks in anticipation.