Weather or not, we're getting warmer

Weather records are one thing, climate another. But one thing is certain, says Robert Henson - we have more warming to come
Robert Henson
guardian.co.uk, Friday 19 December 2008 00.01 GMT

July weather in Britain ... but what does it say about our changing climate?
Like any true football fan or political junkie, I love a good statistic. Those of us who grow up watching the weather - and who now study it, predict it, or write about it - rely on careful, long-term observations. When records are broken, our eyebrows go up and our pulse quickens. We know the difference between a garden-variety record (say, the warmest 12 December ever recorded in Bournemouth) and a truly smashing set (as in Europe's scorching summer of 2003).Even so-called daily records, as in the first example above, can tell a compelling tale when gathered over a long enough period. For nearly a decade, a friend of mine has been patiently tallying record highs and lows reported by NOAA from many hundreds of stations across the United States. Thus far he has counted about 230,000 record highs and about 110,000 record lows. In some years, such as 2008, the ratio is closer than in others. But every year since 2000 has seen more record highs than lows.Climate change has soured my once-wholesome love of statistics like these. I find it harder to take pleasure in a virtually snow-free autumn like the one we just saw in much of Colorado. Almost every fall since 2000 has seen less-than-average snowfall in the Denver area. When you contemplate humanity's influence on the atmosphere, the highs and lows - but especially the highs - become much more ominous.Many people now view weather records as canaries in the coal mine of our greenhouse-goosed atmosphere. The numbers are getting more press than ever. Is this a good thing? Perhaps, if it comes with some perspective on what makes a record more or less meaningful. Otherwise, it is easy to be swayed by those who cherry-pick a show-stopping number as proof or disproof of climate change.Every weather record is only as good as the trail of meteorological bread crumbs that precedes it. Hurricane forecasters were dumbfounded in 2005 when the Atlantic produced 27 named storms. The record was as much linguistic as numeric: for the first time, forecasters ran through the year's assigned list of names and resorted to the Greek alphabet. As remarkable as 2005's burst of activity was, the record was tempered by our spotty knowledge of hurricane counts prior to the advent of satellites and hurricane-hunting aircraft. And there is still much uncertainty on how future hurricane activity in the Atlantic might be exacerbated by warmer oceans in the face of possible changes in upper winds and other factors. Yet there was no denying the bitterness of 2005's hurricane vintage, especially Katrina. That year's unheard-of activity helped galvanise research and focus public attention on what a hyperactive hurricane season can do. Impressive weather statistics can thus be a seen as a broadening of the possible: they tell us that, as we travel into the future, we have to pack for an even wider range of conditions than we thought. When London manages to crack the 100F (37.7C) mark for the first time in 300 years of records, as it did in 2003, we know that something once unthinkable is now something to prepare for.Something of a year-end ritual for climate watchers is waiting for the Met Office, NASA, and NOAA to announce their rankings for annual global temperature. Slight differences in accounting for data-sparse parts of the planet sometimes lead to slightly different rankings among the three groups. By all accounts, though, 2008 looks set to be the least warm year since 2000. This has more than a few climate sceptics claiming that The Great Cooldown has begun.Clearly, a temperature reading averaged across the planet for an entire year is much more significant than a single hot day in London. Yet even the global atmosphere has ups and downs that have little or nothing to do with increased greenhouse gases. If a warm year like 1998 cannot serve as airtight proof that humans are changing the climate, then a coolish year like 2008, or even the relative flatness of the global temperature trend this decade, doesn't mean that longer-term projections of global warming are bogus. Believing that would be equivalent to thinking that spring wasn't coming just because March has brought a frigid week or two.The Australian climate scientist Neville Nicholls has a haiku that neatly summarizes what we most need to remember about climate change. Even for a number-lover like me, this says it all:
The world is warmingFossil fuels are causing this;More warming will come.
• Robert Henson works at the The Rough Guide to Climate Change and The Rough Guide to Weather.