【英语生活】天气预报让你富，也让你穷

Spare a thought for the weather forecasters. Taken for granted when they get it right, they are invariably whipping boys when they get things wrong – despite a far better forecasting record than we economists have. They probably have more to contribute to the economy, too.

A recent case in point: Bournemouth's woes during the bank holiday at the end of May. The Met Office predicted storms, but the beach resort in fact enjoyed the sunniest day of the year. Bournemouth's tourist office reckons the town missed out on at least 25,000 visitors and more than £1m of revenue as a result. Subtler losses and gains were registered by the would-be tourists, and the lucky ones who enjoyed both a sunny day and a quieter beach.

Tourists have always been vulnerable to the weather, but they may now be more vulnerable to weather forecasters. The internet has made it easy to check the forecast and easy, too, to make late bookings for short breaks – which are self-evidently more responsive to the weather.

Galvanised by Bournemouth's woes, I did some research into the economics of weather forecasting for a short BBC documentary. What surprised me was the sheer range of industries that could save money if given a reliable forecast.

Electricity generators need temperature forecasts to gauge the demand for power, and electricity generation itself is weather-sensitive. It's not just a case of windmills and solar panels: gas-fired power stations are more efficient at lower temperatures. Without a good forecast, both energy and money will be wasted.

Local governments are responsible for salting and gritting roads as they freeze. It's a costly process, best avoided if the roads are not, in fact, going to freeze at all. Supermarkets consult detailed weather forecasts and adjust the local product mix accordingly. An extra day's reliable warning of the local weather is a godsend.

The vulnerability to bad weather is even higher in developing countries, sometimes with tragic consequences. As I reported in a column last year, the economists Emily Oster and Ted Miguel have investigated the link between bad weather and “witch” killings. Miguel found that modern-day witch-killings in Tanzania are correlated with droughts and floods. Oster, building on research by historian Wolfgang Behringer, found a connection between cold decades and witch-trials in 16th- and 17th-century Europe.

MIT economist Michael Greenstone has studied the impact of local temperature surges on deaths in both India and the US. He calculates that a year with one extra “heatwave” day – temperatures above 32°C instead of 12°C-15°C – would raise the annual death rate by eight per million in the US. In India, the temperature vulnerability is more than five times higher, notably in rural areas where agriculture suffers and wages drop.

Weather forecasting cannot prevent heatwaves, but it can help in other ways. Accurate forecasts can allow farmers to sow seeds without fear that they will be washed or blown away. A study from the mid-1990s – admittedly, conducted by the World Meteorological Organization – concluded that every dollar invested in weather forecasting services would save $10 in economic losses.

The World Bank broadly agrees, and is supporting Russian efforts to reinvigorate forecasting systems that have been deteriorating since the collapse of the Soviet Union.

The World Bank's researchers reckon that the benefits of such efforts outweigh the costs by five to one. If those numbers stack up, that suggests an unlikely development tactic for poor countries: hire more weather forecasters.

我们不妨替天气预报人员想想。当他们预报准确时，被认为是理所当然的；而当他们预报错了的时候，却总是成为替罪羔羊——尽管他们的预测准确度比我们这些经济学家要强得多。此外，他们或许能为经济作出更大的贡献。

最近的一个例证，就是5月底银行假日期间波恩茅斯(Bournemouth)出现的问题。英国气象局(Met Office)预计，该海滨胜地在假日期间将会出现暴风雨天气，但实际上，那是一年中阳光最灿烂的一天。波恩茅斯旅游局估计，该城至少错失了2.5万名游客和逾100万英镑的收入。那些本打算前往波恩茅斯的游客和（去了的）幸运游客，则分担了说不清楚的损失和收益——那些幸运的游客既享受了阳光灿烂的一天，也享受了更为安静的海滨。

游客总是容易受到天气的影响，而现在他们或许更容易受到天气预报的影响。互联网使得查看天气预报变得较为容易，也为短期休假的推迟预订提供了便利——无疑这更容易根据天气进行调整。

受波恩茅斯事件的影响，我对天气预报经济学进行了一些研究，用于英国广播公司(BBC)的一个记录短片。我惊奇地发现，如果天气预报可靠的话，会有许多行业能够省钱。

发电厂需要天气预报来判断电力需求，而发电本身就对天气较为敏感。不仅风力发电或太阳能电池板与天气有关：燃气发电厂在低温下效率会更高。没有可靠的天气预报，会浪费能源和金钱。

地方政府有责任在道路结冰时撒上盐和沙砾。这是一种费用高昂的做法，实际上最好是能够避免道路结冰。超市会查询详细的天气预报，并相应调整当地的产品搭配。多一天可靠的当地天气预报，无异于一种上天的恩赐。

发展中国家甚至更容易受到恶劣天气的影响，有时还会造成悲剧性的后果。正如去年我在专栏中写道的那样，经济学家艾米丽•奥斯特(Emily Oster)和泰德•米格尔(Ted Miguel)调查了恶劣天气和“女巫”被杀之间的关联。米格尔发现，当代坦桑尼亚杀害女巫案例与干旱和洪水有关。在历史学家沃尔夫冈•贝林格(Wolfgang Behringer)研究的基础上，奥斯特发现，在16世纪和17世纪的欧洲，几十年的寒冷天气与审判女巫之间存在关联。

麻省理工学院(MIT)经济学家迈克尔•格林斯通(Michael Greenstone)对印度和美国当地气温飙升对死亡率的影响进行了研究。他估计，如果一年额外多一天“高温天气”——气温高于32摄氏度，而不是12至15摄氏度——美国每百万人每年的死亡率就会增加8人。在印度，高温造成的死亡率是美国的5倍多，特别是在农作物歉收、薪资下降的农村地区。

天气预报无法阻止高温天气的出现，但在其它方面会有所帮助。准确的天气预报可以使农民放心播种，而不用担心种子被雨冲掉或被风吹走。世界气象组织(WMO)从上世纪90年代中期开展的研究表明，在天气预报服务上每投入1美元，就会减少10美元的经济损失。

世界银行(World Bank)对此基本表示赞同，并支持俄罗斯重建自苏联解体以来日益衰落的天气预报系统。

世行的研究人员预计，此类努力带来的益处与成本的比例为五比一。如果把这些数据汇总起来，就意味着穷国应采取一种不太可能的发展战略：聘用更多的天气预报人员。

译者/君悦