Can't stand the heat? Plant trees

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The Independent Culture
HOT, ISN'T it? Or at least it was. For a few days, most parts of Britain have sweltered, while other parts suffered thunderous downpours that threatened to turn Pendeford, near Wolverhampton, into a potential canyoning venue. July was the driest on record - beating even the summer of punk, 1976.

In the United States, the hot weather has had a more deadly edge, with more than 150 people dead from baking weather in the mid-West, most notably in Chicago, where the temperature was above 35C. The record books have been consulted again, and left gasping, over the heat in New York, where it has never been so hot so often in a single month (11 days with temperatures in excess of 35C).

At this point, you may be expecting a telling-off about how this is all down to global warming, and in particular, that trip you took to the out- of-town supermarket on Saturday in the car, when you should have waited for one of John Prescott's wonderful buses to take you there.

But that's probably not going to help now. Science is nothing if not pragmatic. The best projections reckon that the world's average surface temperature will rise by between 2 and 6 degrees in the next century. By comparison, when the last Ice Age was at its worst, roughly 19,000 years ago, the world was between 5 and 9 degrees colder than it is now.

The more salient point, though, is that, with climate change getting well-established, the likelihood is that summer heatwaves, and the sort of freak weather-events such as the whirlwind that hit an antiques fair in Kent on Saturday, will become more common - as will winter storms. It's not that every summer will be somewhere between 2 and 6 degrees hotter, and no more. It's that the swings will be centred around such an increased reading.

Now, what should we do about this? Perhaps the most sensible thing is to get used to it. You and your children are going to be living in weather that will, at times, be uncomfortably hot. It will be like living further south.

But is it really likely that we will turn to siestas and four-hour lunches in order to accommodate ourselves to the changing climate? That would be nice, but it's doubtful. The pell-mell nature of modern capitalism won't let us slow down. Perhaps some of the people who died in the US would be alive now if only they had lived in a siesta culture. But where there's money to be made from closing a deal at 2pm rather than 4.30pm, people will push for that to be the case. Siestas will be for wimps.

Equally, it would be nice to think that City folk will come to work in Birkenstock sandals and shorts, but that's not going to happen without a major culture shift - it's more likely people will start taking buses rather than their cars for commuter trips on the M4. Human nature is too resistant to short-term change, even when threatened by long-term danger.

Should we just lay in electric fans and air conditioners? No: actually all they do is to redistribute heat, making things worse. Run a fan in a closed room and you'll end up hotter, not cooler. New York's fabled boiling summers are made worse, not better, by the widespread use of powered air-coolers. What would work is, literally, a greener approach to living in cities. We need to plant more trees, because, as a recent study of data spanning more than 25 years shows, trees can do more to cool a city than almost anything.

Dale Quattrochi, of the Global Hydrology and Climate Center in Huntsville, Alabama, who investigated the data that led to those conclusions, pointed out some startling statistics. Roads and asphalt pavements absorb heat and re-radiate it as more heat. Infra-red pictures of a parking lot on a day in 1994 found that the temperature registered as much as 48C (120F); but a group of "tree islands" on the pavements and roads nearby recorded 31C (89F) - which is clearly still hot, but is, by comparison, significantly cooler .

Just as important was the way in which the parking lot stayed hot even at night, at about 24C, while the "tree islands" were 17C. Trees are even better than open grassland, because they offer the sort of shade that an open space cannot. (The reason why trees stay cooler is that they contain water, which is slower to heat up than solids are.)

With Mr Prescott's ambitious transport plans stumbling, he should shift the emphasis. Maybe he can't get the trains to run on time (or run at all, in some cases). Perhaps backing for his road-tolling systems is tardy. So it's time for him to concentrate on a simpler pledge. How about planting an urban tree for every car sold? If you can't beat the roads lobby - tackle it at the grassroots, or tree-roots, level.

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