Open Data vs Global Warming

Thursday, December 24. 2009

Open Data vs Global Warming

Average Temperature, Port Elizabeth, since 1880.

Given all the hoo-ha around Global Warming, Climate Change and those leaked emails, it has been rather fascinating to play around with Geo-Me, a Tim Berners-Lee inspired Open Data project that mashes up temperature records from weather recording stations globally, some of which have been running for 300 years. For the first time it has been easy to get at the raw data oneself.

The (un?)intended consequences, I suspect, are profound - in that anybody looking at these (I've looked at about 20 around the planet from places I've been to, mainly airports - sad, I know) is going to go "Um, so where exactly is all this global warming then?". Never mind man-made (anthropomorphic) global warming or AGW!

Its an inconvenient truth, but the benefits of Open Data cut many ways, pulling down myths with little respect for whose they are.

For your delectation I have put up Port Elizabeth in South Africa above, where temperatures are logged since 1880 in their database (in fact its been recorded soon after the 1820's when my forebears landed there) and as you can see, the increase has been tiny - and explained more by PE 's expansion as a deep-water port city (and thus the heat island overrunning the recording station) in the 1960's.

Or, to put it in the local vernacular - Anthropomorphic Global Warming? Ek kan fokol daar sien, man!

(For the record, I believe it is quite possible to want sustainable resource usage and a diminution of fossil fuel dependence - "Classical Green" I think the shade is now called

- without buying Climate Change or AGW)

Posted by Alan Patrick in Open Source at 21:11 | Comments (4) | Trackbacks (0)

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Alan - your post is an excellent example of how someone without basic math skills can easily misinterpret data to incorrectly bolster a pre-existing prejudice. It is a problem because scientific understanding is not always obvious and data trends can be subtle. Your analysis is the equivalent of throwing the numbers on the floor and proclaiming that because you cannot see the pattern, there must be none.

Here is how to go about it:

1. Go the Met Office site http://www.metoffice.gov.uk/climatechange/science/monitoring/subsets.html

2. Get the basic data, as you did, from the Met Office http://j.mp/5E0U8X or http://www.metoffice.gov.uk/climatechange/science/monitoring/reference/68/688420

3. Read the explanation on the Met site about average temperatures and how to understand them http://www.metoffice.gov.uk/climatechange/science/explained/explained5.html

In particular note" Absolute temperatures are not used directly to calculate the global-average temperature. They are first converted into ‘anomalies’, which are the difference in temperature from the ‘normal’ level. The normal level is calculated for each observation location by taking the long-term average for that area over a base period. For HadCRUT3, this is 1961–1990."

4. Using the dataset you downloaded, note the "normal" temperatures: Normals= 21.3 21.1 20.3 18.2 16.1 14.4 13.9 14.3 15.4 16.7 18.2 20.0

5. Average the monthly figures to get the annual "normal" temperature of 17.492

6. In a spreadsheet, for each year, average the 12 monthly temperature and then calculate the difference from the normal temperature (plus or minus)

7. Plot the differences and you get a graph like this http://bit.ly/8BDlYX

8. Now you can see the increase.

Now one problem you had was that you think the increase is "tiny" and so you disregard it, without being specific as to what "tiny" is or what the actual reported global average temperature rise has been. The graph shown in the Met Office site is http://j.mp/4Gavxf http://www.metoffice.gov.uk/climatechange/science/monitoring/data-graphic.GIF and the range of differences from the normal (1961 to 1990) is very similar to that at PE.

The broader issue here is that it sometimes takes a bit of digging and analysis to see the trend.

#1 david sanger (Homepage) on 2009-12-25 04:54 (Reply)

Alan: apparently I misunderstood the source of your graph. I thought you had created it yourself but it turns out to be created by geo.me

My analysis stands, and it is they who have the misleading data graph.

#2 david sanger (Homepage) on 2009-12-25 05:15 (Reply)

Hi David - that's a fascinating bit of work, thanks you for it. I know what the normalizing calcs do, they bring out the difference to the mean so its easier to see - I actually added a straight line in my graph (see the lower one) to eyeball the same trend here. I have a love of raw data as you know exactly where you are with it - the CRU is hardly the by-word for a trusted source right now!

The issue to me is the "what does it imply" issue - is is this material or tiny? In summary, my pushback to the AGW argument is that:

- This (and nearly every graph I have looked at) is no "hockey stick", and if you look at most datapoints globally they don't show the large uptick the AGW crowd argue for - hence relatively "tiny".

- The data does not contradict another (in my view more likely) explanation vs AGW, which is a longer cycle rise from the low of the "little ice age" in the late medieval period, probably to a time warmer than today in the dark age/feudal period when things were demonstrably warmer (settlement patterns in Greenland, grapes grown in Yorkshire etc) - ie AGW is not provably the cause.

As to Global Warming itself as a theory, that is more believable given the cycle above - but I would hypothesize overall that those stations reporting the largest recent rises are those nearest expanding cities.

This rise in PE is as easily explained by the local condition of the PE heat island as it expands over the weather station. If you look further inland to Aliwal North which has not expanded much, the temperature (over the same period) actually is decreasing.

(Re the lack of maths skills, I'm afraid I have 2 degrees in Engineering and they shoved a lot of maths at us

#3 alan p on 2009-12-25 21:53 (Reply)

For discussions and background analysis and links to source papers I highly recommend http://www.realclimate.org . It is worth taking the time to thoroughly research issues, read the comments to and fro, and is a much better place for commenting and conversation. My sense is that serious questions are generally answered with care.

re the Hockey Stick, it is easier to see if the PE data is plotted on a graph of the same dimensions; of course the instrumental record only covers the last 120 or so years.
http://j.mp/5gvEfO vs. http://j.mp/4Os0yO

source : Temperature Variations in Past Centuries and the so-called "Hockey Stick" http://j.mp/5N3x5g

re the Urban Heat Island Effect, this writeup has some of the background research papers :

The Surface Temperature Record and the Urban Heat Island http://j.mp/7HNw9G

re: CRU data:

Are the CRU data “suspect”? An objective assessment. http://j.mp/8e9Oox

I'd add that the authors of these papers are in a much better position to engage and discuss these issues than I am, and I'd encourage you to participate in the active, informational, lively and generally respectful and on-topic discussions there.

regards david.

and understand on the maths

#4 david sanger (Homepage) on 2009-12-26 17:23 (Reply)

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