Wednesday, 17 February 2010

How I made the Met Office admit its climate-change data was wrong

John Graham-Cumming

The history of science is filled with stories of amateur scientists who made significant contributions. In 1937 the American amateur astronomer Grote Reber built a pioneering dish-shaped radio telescope in his back garden and produced the first radio map of the sky. And in the 19th century the existence of dominant and recessive genes was described by a priest, Gregor Mendel, after years of experimentation with pea plants.
But with the advent of powerful home computers, even the humble amateur like myself can make a contribution.
Using my laptop and my knowledge of computer programming I accidentally uncovered errors in temperature data released by the Met Office that form part of the vital records used to show that the climate is changing. Although the errors don’t change the basic message of global warming, they do illustrate how open access to data means that many hands make light work of replicating and checking the work of professional scientists.
After e-mails and documents were taken from the Climatic Research Unit at the University of East Anglia late last year, the Met Office decided to release global thermometer readings stretching back to 1850 that they use to show the rise in land temperatures. These records hadn’t been freely available to the public before, although graphs drawn using them had.

Apart from seeing Al Gore’s film An Inconvenient Truth I’d paid little attention to the science of global warming until the e-mail leaks from UEA last year.
I trusted the news stories about the work of the IPCC, but I thought it would be a fun hobby project to write a program to read the Met Office records on global temperature readings and draw the sort of graphs that show how it’s hotter now than ever before.
Since my training is in mathematics and computing I thought it best to write self-checking code: I’m unfamiliar with the science of climate change and so having my program perform internal checks for consistency was vital to making sure I didn’t make a mistake.
To my surprise the program complained about average temperatures in Australia and New Zealand. At first I assumed I’d made a mistake in the code and used a pocket calculator to double check the calculations.
The result was unequivocal: something was wrong with the average temperature data in Oceania. And I also stumbled upon other small errors in calculations.
About a week after I’d told the Met Office about these problems I received a response confirming that I was correct: a problem in the process of updating Met Office records had caused the wrong average temperatures to be reported. Last month the Met Office updated their public temperature records to include my corrections.
John Graham-Cumming is a programmer and author of The Geek Atlas