A version of this article appeared in the Southern Highland News, 25 September 2013, under the title “Not an exact science”. More articles from the CANWin column.
Prediction is very difficult, especially about the future. Niels Bohr
A great big report is coming out this week. It’s called “Climate Change 2013: The Physical Science Basis”, and it’s been prepared by “Working Group 1 of the Intergovernmental Panel on Climate Change”, the IPCC. Three more massive reports will follow, one each from Working Groups 2 and 3, and then in October next year a synthesis report for policymakers that pulls them all together.
You might already have seen stories in the media suggesting that this first report “admits” that earlier predictions were wrong. Here’s a tip: when a reporter or a blogger talks about an IPCC prediction, there’s probably something wrong with the story.
For example, a couple of weeks ago a story did the rounds about sea ice in the Arctic. The story was that the IPCC predicted that sea ice would be gone by 2013, and instead it increased. There’s something wrong with both parts of that story.
Sea ice is frozen sea water. It grows in winter and melts in summer. In the northern summer of 2012 the Arctic sea ice melted to the lowest amount on record. In the summer just ended it melted to the 6th lowest amount on record. That’s more than last year, but still less than any year before 2005. It’s also 70% less than in the 1980s. Funny kind of increase!
The second problem is that the so-called IPCC prediction never happened and never would. Such a precise prediction would be like a life insurance company predicting the exact date of one person’s death. Insurers work with probabilities and uncertainty, and so does the IPCC.
When we think about how long we can expect to live, we need to remember that it depends partly on what we do in the time we’ve got left.
When we read about predictions in the new report, we need to remember that what happens to the Earth’s climate depends largely on what humans do from now on about greenhouse gases.
You’ll be able to see the report for yourself, starting with the summary for policymakers, which will be available from 30 September at http://www.climatechange2013.org/