It's weather, not climate

Variability matters more than trend

By Matt Ridley

The east wind could cut tungsten; the daffodils are weeks behind; the first chiffchaffs are late. It’s a cold spring and the two things everybody seems to agree upon are that there’s something weird about the weather, and it’s our fault. Both are almost certainly wrong.

On weird weather, it is true that the contrast with last year’s warm March is striking, as is the difference between the incessant rain of the last twelve months and the long drought that preceded it in most of England. In the last year, America’s had a heatwave, a superstorm and now a bitterly cold spring. Australia has just had an “angry summer”. And so on.

The government’s retiring chief scientist, Sir John Beddington, claimed this week that “we are seeing more variability”. Is he right? On the whole, no. Forget the anecdotes and examine the data.

Start with America. Professor Roger Pielke of the University of Colorado has documented that floods, hurricanes, tornadoes and east-coast winter storms have shown no increase since the 1950s, while droughts have shown a slight decrease. The only thing that has changed is the financial damage done by storms, but as he drily remarks “The actual reason for the increasing number of damaging tropical storms has to do with the reporting of damages.”

What about elsewhere in the world? There has been no trend in tropical cyclone intensity or frequency worldwide at all. The Intergovernmental Panel on Climate Change itself, though heavily infiltrated by environmentalists in recent years, stated in a recent special report on climate extremes that over the coming two to three decades “signals are relatively small compared to natural climate variability” (as Matthew Parris pointed out last week, don’t you hate this habit of making forecasts in the present tense?), and that “even the sign of projected changes in some climate extremes over this time frame is [sic] uncertain”. Translated: the weather is just as likely to become less extreme as more extreme.

So why is everybody convinced otherwise? Partly because they have been listening too much to the big insurance companies, which have a vested interest in bidding up our anxiety, as Dr Pielke’s remark reminds us. Also it seems even government chief scientists suffer from what psychologists call “availability heuristic” – when people judge the probability of events from how easy it is to think of examples. Here’s an instance: “I cannot recall such a cold March”, says a man with dim memories of 1963 as he reads a Met Office report that March 2013 is the coldest in Britain since…1963. Do you remember March 1963? I don’t.

So next time some pub bore tells you this cold month is caused by the extensive melting of Arctic sea ice last summer, ask him if the same thing happened in 1983. In any case, even if there were evidence for changing weather, blaming every weather event on climate change is lazy at best and dishonest at worst. As I wrote in these pages during the cold December of 2010, “It's not climate change. It's weather: just a cold snap.”

Not that politicians took my advice. Mayor Michael Bloomberg of New York and Governor Chris Christie of New Jersey were quick to blame “superstorm” Sandy on climate change not least because it was a convenient way to deflect blame for the disastrous power and fuel shortages that afflicted communities for so long after the storm.

There was perhaps an echo of this last month when Lord Smith, chairman of the Environment Agency, incautiously blamed recent flooding on “increasing instances” of “convective rain, which sits in one place and just dumps itself in a deluge over a long period of time.” Not only did this sound to annoyed flood victims and their MPs as an excuse; it drew a sharp rebuke from the veteran weather forecaster Bill Giles, who said “There is nothing new about convective rain. Perhaps next time he should get a meteorologist to check his answers.”

As we have just experienced in a year, the variability of weather matters far more than the trend in climate. Noise matters more than signal. The world grew about half a degree warmer in the last third of the twentieth century, but the difference between March 2012 and March 2013 was almost ten times as great as that (7.7C vs 3.1C).

Suppose we get another half a degree of warming in the next three decades – and we may well do, even though there’s been no net global warming now for 16 years and the latest peer-reviewed studies (from James Annan of the Japan Agency for Marine Earth Science and Technology, Magne Aldrin of the Norwegian Computing Center and Michael Schlesinger of the University of Illinois among others) all confirm that the climate is less sensitive to carbon dioxide than the IPCC has been saying. That warming would be one-tenth as much change over 30 years as we just experienced between two versions of March in consecutive years. It would be equivalent to moving house to a new village 250 feet lower down a hill (temperature changes by 0.65C per 100 metres of altitude), or a couple of counties to the south.

It would also be about one-quarter as much warming as you would experience if you moved from rural Surrey to central London. Nearly all the stories of recent years about how much earlier flowers have been blooming came from within the massive urban heat island that is London: Kew for example has experienced more local warming than it has global warming. There is much less evidence of changing seasons from rural Britain. My diary records of the date I first heard first chiffchaff sing since 1986 show lots of variation, but no trend at all.

In the heyday of climate-change mania of a few years ago we were all told to plant cacti and drought resistant lawn grass. Yet we’ve just had a run of three out of four hard winters and they killed off the eucalypts and Wollemi pines my father planted in his arboretum. It’s a racing certainty that you will still have to plan for occasional hard winters and you won’t have to tell your children what snow is.

The lesson that weather matters more than climate is not just a bit of fun. Airports and our councils forgot to plan for snow a few years ago, because they were more focused on the trend than the variability. In 2010 Brisbane disastrously overfilled a dam because it expected drought to return; the dam could not absorb a flood when it came.

Climate is what you expect; weather is what you get. Which is presumably what the first chiffchaffs will be soon be saying to themselves as they desperately search the barren tree branches for frozen insects