# Comparing all the temperature records

I’ve added a new graphic to the list of Hi-rez Climate Graphics: a composite of all the major global temperature records, going back to 1890 (obviously the satellite records [RSS and UAH] only begin in the late 20th century). Many thanks to Benjamin Franz who sent me the spreadsheet of all the data

I’m reposting some pieces by physicist John Cook, who runs Skeptical Science.

Benjamin has published a series of useful graphs including a version of the graph above. The data comes from surface temperature measurements of NASA GISS, HadCRUT, NOAA plus the satellite measurements of lower atmosphere temperature by RSS and UAH. The data was originally compiled by Kelly O’Day from Climate Charts and Graphs who put all 5 datasets into a single spreadsheet. The problem is all the different temperature records use different base periods.

Temperature records are expressed as an anomaly (or variation) from a specified base period. For example, the base period for both satellite recoreds (UAH and RSS) is 1979 to 1998. So for example, when the UAH record says 0.5°C, it actually means the temperature is 0.5°C warmer than the average temperature over 1979 to 1998. The GISS base period is 1951 to 1980. HadCRUT use the base period 1961 to 1990. NOAA use 1971 to 2000. The choice of base period doesn’t really matter as its the trend that’s important, not the absolute values. Nevertheless, some people do get a little confused when comparing two temperature records that use different base periods.

To get around the problem of different base periods, Benjamin normalised all the datasets by calculating each temperature record’s average value over the period 1980 to 2010. Then he calculated the temperature anomaly from the 1980 to 2010 base period. Thus each record now used the same base period and could be directly compared.

As surface temperature is a noisy signal, with plenty of variation from year to year, Benjamin calculated the long-term trend by calculating the 133 month moving average. That is what is shown in the graph above. The graph is also available in a number of formats:

Now I would love to add the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis to this graph. The ECMWF record covers the full globe but uses an independent technique to NASA to estimate warming in the Arctic regions. Their data is available on their website but I’ve never been able to penetrate their obtuse interface (no offence to the good folk at the ECMWF). So if anyone is able to post a link to the pertinent data or even better, hand it to me on a silver platter in Excel format (hint, hint), please be my guest :-)

P.S. – for a more rigorous treatment of this subject, Tamino at Open Mind has two recent blog posts worth a look: Odd Man Out and Comparing Temperature Data Sets.

– John Cook, “Comparing all the temperature records.”

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### 10 Responses to Comparing all the temperature records

1. caerbannog says:

We’ve had unusually rainy weather in San Diego (even for this time of year). So that gave me some time to sit down in front of the computer and play with some temperature data. Since deniers like Anthony Watts have long accused NASA/NOAA, etc. of “fudging” the temperature data with adjustments to get a warming trend, I decided to throw together a crude “back of the envelope” comparison of raw vs. adjusted GHCN data.

I put together a little program to compute simple unweighted temperature anomaly averages of all the GHCN land temperature stations. No fancy geospatial weighting or gridding — just simple dumb averaging. Of course, that means that places where temperature stations are clustered will be “overweighted”, so I didn’t compute a very good global average.

But what I *was* able to do was directly compare raw vs. adjusted data results as well as look at the behavior of monthly maximum vs. mean vs. minimum temperatures over time.

It turns out that (surprise, surprise) the raw and adjusted temperature data produced almost identical average anomaly results. The results were pretty similar to NASA’s results (but noisier due to lack of ocean temperature coverage as well as the overweighting problem mentioned above).

All of the data sets showed a pronounced warming trend over time. The differences between the raw and adjusted temperature results were *very* small. So all of the denier howling about “adjustments” to temperature data really is much ado about nothing.

The monthly maximum data showed a pronounced mid-20th century cooling trend, while the monthly minimum data did not.

Overall, my results were quite consistent with NASA/NOAA/CRU/etc results and were quite consistent with global-warming theory (minimum temperatures rising faster than maximum temperatures, mid-20th century aerosol cooling affecting maximum temperatures far more than minimum temperatures).

I did this in a couple of afternoons (with lots of interruptions for distractions) — IOW, I performed more data analysis in a few hours than Anthony Watts has in his entire life!

2. Richard L says:

I try to talk climate with my non-interested family and friends and there are few graphs that are very useful to get their attention and convey clear and understandable information to non-technical people. I try to discuss very basic concepts in layman’s terms (I am an engineer, but a climate layman myself).

I fear that this graph, although showing a clear trend, would invoke a response of “we were below zero for so long, now we went back to normal and are high, and natural variation seems to make sense”

Scientists can define “anamolies” and “base periods”, but I think the lay person will see ‘below zero’ and lose perspective.

Is there a way to present this information that will provide a clearer message to the lay person?

3. Windsong says:

This is really, really good! I plan to copy this (hopefully in color) and distribute it. Deniers can’t deny this!!

4. Lazarus says:

The UK is having it’s coldest winter since 1910.
I think it is interesting to look at the graph above and compare 2010 to 1910 to see the global temperatures. It just goes to show what an anomalous year the UK is having.

5. caerbannog says:

I fear that this graph, although showing a clear trend, would invoke a response of “we were below zero for so long, now we went back to normal and are high, and natural variation seems to make sense”

Maybe the plot should be redone with these small changes: Add the 1980-2010 baseline temperature to the y-axis label values (while keeping the overall scale the same) and change the y-axis label to “global average temperature…”.

6. question says:

Nice graph. But before I use this to try to convince people they are going to want a clear explanation for what drove the temperature rise from 1910 to 1940. It clearly wasn’t CO2 from human sources since the human contribution was fairly insignificant during that time period. For someone who understands the science the fact that CO2 is a greenhouse gas doesn’t change just because there were natural variations before. But that doesn’t change the psychology of argument. Critics/deniers will say “but look at that, the warming in 1910-1940 was nearly as large as the climate nuts are whining about now, but it wasn’t CO2 then, and it isn’t now!” It doesn’t matter that that is a logical fallacy. How do we answer it when trying to convince people? If we can say “that was due to such and such. measurements show it isn’t happening today”, we’ll be a much stronger place for arguing.

[JR: Explained/rebutted a long time ago. See here.]

7. caerbannog says:

Critics/deniers will say “but look at that, the warming in 1910-1940 was nearly as large as the climate nuts are whining about now, but it wasn’t CO2 then, and it isn’t now!”

Here’s a slam-dunk rebuttal against that old denier argument:

Increasing CO2 concentrations impact *minimum* temperatures much more than maximum temperatures. Solar and volcanic activity, in contrast, have much more impact on maximum temperatures than on minimum temperatures.

What I found from my little data-crunching exercise (post 1 above) is that the increase in *minimum* temperatures from 1970-2010 was *much* greater than the increase in minimum temperatures from 1910-1940. In fact, I saw only a slight warming trend in the minimum temperatures during the 1910-1940 period. But after about 1970, minimum temperatures skyrocketed.

My own results were entirely consistent with warming due to solar/volcanic activity prior to 1940 and strong CO2-forcing post-1970. The signatures could not have been more clear.

In summary: 1910-1940 — significant increases in monthly “maximum” temperatures, but only slight increases seen in monthly minimum temperatures. The post-1970 period showed increases in both minimum and maximum temperatures, with an especially strong increase in monthly minimum temperatures. The differences between the 1910-1940 and post-1970 periods are really quite striking.

My response to deniers is “If you don’t believe me, feel free to crunch the data yourselves, and if you don’t have the technical skills to do that, then you have no business arguing about this topic.”

8. Richard L says:

Sorry for the repetition, but I do wonder why the baseline is chosen so there are negative numbers? Why not choose 1910 as the base period so everything looks positive?

And to explain my focus on this, I have a short illustrative story.

I am an environmental engineer by training and occupation for almost 20-years. A few years ago I ‘started over’ and began training in solar energy and energy efficiency thanks in part to the shocking wake up call from An Inconvenient Truth. In the energy efficiency training, there were a series of calculations for vacuum testing of buildings (i.e. negative pressures) to find air leaks. The trainers, who were highly experienced in presenting this material, explained the results using the term ‘bigger numbers’ for ‘higher vacuum.’ I complained that ‘bigger’ means ‘less negative’ not ‘more negative.’ They said that almost all of the folks they train can’t understand negative numbers.

It is my sense that a large part of the public fall into this category. The only negative number many may see is an overdraft on their bank account…. and IMO the public must be woken up to get our politicians to follow. I often ask myself how can we wake them when they can’t understand the science? How can I explain in basic understandable terms….

9. question says:

Thanks Joe, this is exactly what I was looking for. It’ll make a nice rebuttal when folks I know bring it up.

10. Chris Winter says:

Just FYI, the link on the relevant Skeptical Science page to Tamino’s more detailed explanation (“volcanic lull”) is broken.

The correct URL is: http://tamino.wordpress.com/2010/08/23/antrhopogenic-global-cooling/

Yes, that’s how it’s spelled. The blog software picked up a typo.