Reading sections of the mainstream press at the moment, it would be easy to come to the conclusion that climate change has stopped. The truth is somewhat different, and this post from RealClimate explains how some statistics are being very carefully cherry-picked in order to present a highly distorted perspective
The great thing about complex data is that one can basically come up with any number of headlines describing it – all of which can be literally true – but that give very different impressions. Thus we are sure that you will soon read that 2008 was warmer than any year in the 20th Century (with the exception of 1998), that is was the coolest year this century (starting from 2001), and that 7 or 8 of the 9 warmest years have occurred since 2000. There will undoubtedly also be a number of claims made that aren’t true; 2008 is not the coolest year this decade (that was 2000), global warming hasn’t ‘stopped’, CO2 continues to be a greenhouse gas, and such variability is indeed predicted by climate models. Today’s post is therefore dedicated to cutting through the hype and looking at the bigger picture.
As is usual, today marks the release of the ‘meteorological year’ averages for the surface temperature records (GISTEMP, HadCRU, NCDC). This time period runs from December last year through to the end of November this year and is so-called because of the fact that it is easier to dice into seasons than the calendar year. That is, the met year consists of the average of the DJF (winter), MAM (spring), JJA (summer) and SON (autumn) periods (using the standard shorthand for the month names). This makes a little more sense than including the JF from one winter and the D from another as you do in the calendar year calculation. But since the correlation between the D-N and J-D averages is very high (r=0.997), it makes little practical difference. Annual numbers are a little more useful than monthly anomalies for determining long term trends, but are still quite noisy.
The bottom line: In the GISTEMP, HadCRU and NCDC analyses D-N 2008 were at 0.43, 0.42 and 0.47ºC above the 1951-1980 baseline (respectively). In GISTEMP both October and November came in quite warm (0.58ºC), the former edging up slightly on last month’s estimate as more data came in. This puts 2008 at #9 (or #8) in the yearly rankings, but given the uncertainty in the estimates, the real ranking could be anywhere between #6 or #15. More robustly, the most recent 5-year averages are all significantly higher than any in the last century. The last decade is by far the warmest decade globally in the record. These big picture conclusions are the same if you look at any of the data sets, though the actual numbers are slightly different (relating principally to the data extrapolation – particularly in the Arctic).
So what to make of the latest year’s data? First off, we expect that there will be oscillations in the global mean temperature. No climate model has ever shown a year-on-year increase in temperatures because of the currently expected amount of global warming. A big factor in those oscillations is ENSO – whether there is a a warm El Niño event, or a cool La Niña event makes an appreciable difference in the global mean anomalies – about 0.1 to 0.2ºC for significant events. There was a significant La Niña at the beginning of this year (and that is fully included in the D-N annual mean), and that undoubtedly played a role in this year’s relative coolness. It’s worth pointing out that 2000 also had a similarly sized La Niña but was notably cooler than this last year…
A less technical, more opinion led piece looking at some of the online reactions to news regarding climate change can be found on George Monbiot’s blog
We all create our own reality, and shut out the voices we do not want to hear. But there is no issue we are less willing to entertain than manmade climate change. Here, three worlds seem to exist in virtual isolation. In the physical world, global warming appears to be spilling over into runaway feedback: the most dangerous situation humankind has ever encountered. In the political world – at the climate talks in Poznan for example – our governments seem to be responding to something quite different: a minor nuisance which can be addressed in due course. Only the Plane Stupid protesters who occupied part of Stansted airport yesterday appear to have understood the scale and speed of this crisis. In cyberspace, by contrast, the response spreading fastest and furthest is flat-out denial.
The most popular article on the Guardian’s website last week was the report showing that 2008 is likely to be the coolest year since 2000(1). As the Met Office predicted, global temperatures have been held down by the La Nina event in the Pacific Ocean. This news prompted a race on the Guardian’s comment thread to reach the outer limits of idiocy. Of the 440 responses posted by lunchtime yesterday, about 80% insisted that manmade climate change is a hoax. Here are some clips from this conversation:
“This is a scam to get your money. …The only people buying into “global warming” have no experience with any of the sciences”.
“If we spend ANY money or cost one person their job because of this fraud it would be a crime. When will one of our politicians stand up and call this for what it is, BULLSH1T!”
“What a set of jokers these professors are … I think I understand more about climate change than them and I don’t get paid a big fat salary with all the perks to go with it.”
And so on, and on and on. The new figures have prompted similar observations all over the web. Until now the “sceptics” have assured us that you can’t believe the temperature readings at all; that the scientists at the Met Office, who produced the latest figures, are all liars; and that even if it were true that temperatures have risen, it doesn’t mean anything. Now the temperature record (though only for 2008) can suddenly be trusted, and the widest possible inferences can be drawn from the latest figures, though not, of course, from the records of the preceding century. This is madness.
Scrambled up in these comment threads are the memes planted in the public mind by the professional deniers employed by fossil fuel companies(2). On the Guardian’s forums you’ll find endless claims that the hockeystick graph of global temperatures has been debunked; that sunspots are largely responsible for current temperature changes; that the world’s glaciers are advancing; that global warming theory depends entirely on computer models; that most climate scientists in the 1970s were predicting a new ice age. None of this is true, but it doesn’t matter. The professional deniers are paid not to win the argument but to cause as much confusion and delay as possible. To judge by the comment threads, they have succeeded magnificently.
Happy new year.
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