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445|25 Vol January 2007 SPECIAL REPORT Saving time Politicians in the United Kingdom and United States have launched efforts to extend daylight-saving measures hoping to save lives, cut power use and combat carbon emissions. But energy experts say that it s not that easy. Michael Hopkin reports. On 26 January, the British parliament will vote on whether to turn its back on a cherished piece of the country s heritage: Greenwich Mean Time, long the standard against which the world s clocks were set. Under the proposal, Britons would set their watches forward an hour year-round, putting them on the same time as the rest of Europe, and never on Greenwich time. If adopted, the measure would give Britain an extra hour of daylight in the evening. Backers argue that the proposal could cut automobile accidents, saving more than 100 lives per year, and slash demands on the country s power grid, saving carbon emissions equivalent to those generated by 70,000 people in a year. British clocks would still go forward an hour every spring and back again in autumn, just as they have almost every year since 1916, when the country adopted British Summer Time. Under the new scheme, which would be trialled for a period of three years, clocks would be set an hour ahead of Greenwich in the winter, and two hours ahead in summer a regime called single-double summer time . But history shows that such seemingly simple changes are not made easily. A similar experiment in the late 1960s failed, mainly because of parents complaints about children going to school in the dark and the grumblings of farmers and other outdoor workers. Energy experts say that it s not so easy to calculate the true benefits for the environment. The move comes as US citizens prepare for a longer summer, by pushing their clocks forward on 11 March three weeks earlier than usual. US politicians have claimed that the country will save 100,000 barrels of oil per day, but will wait until the scheme is underway to 344 The UK bill to bring the clocks forward could change the face of London s time. gather detailed data on changes in energy use. Both the British and US policies are extensions of the current scope of daylight-saving time (DST), which is practised in roughly 70 countries, almost all of which are at temperate latitudes. DST artificially shifts the time of dawn and dusk forward by an hour during the long summer days, providing an extra hour of light in the evenings. As the winter days draw near, the clocks are put back again so that mornings don t become unbearably dark. But the DST scheme can be taken further, argues Elizabeth Garnsey, an innovation researcher at the University of Cambridge, UK, who has evaluated the probable effects of the proposed changes to the British system. Countries are starting to realize that their daylight-saving policies haven t really been saving daylight, she says. Moving the clocks forward yet another hour would produce a slew of benefits, she says. The reduced need for lighting in the afternoons could save around 485 million (US$957 million) a year, as well as 170,000 tonnes of carbon dioxide. Preliminary calculations cited by the proposal s backers suggest that domestic lighting bills could dip by 0.8%, whereas commercial spending could be cut by 4% as more working days finish during daylight. And because the late afternoon is also the time of peak power demand, analysts at National Grid, which coordinates Britain s power supply, A. WOOLFITT/ROBERT HARDING WORLD IMAGERY/CORBIS NATURE|Vol 445|25 January 2007 NEWS CLIMATE SATELLITES Researchers detail their wish list to avoid fatal gaps in measurement. www.nature.com/news Daylight-saving time (DST) has a long and chequered history popular in some time periods, not so in others. 1784 The idea of shifting clocks to make better use of daylight hours is first proposed by Benjamin Franklin in a satirical letter to the Journal of Paris. He later whimsically suggests that people be taxed for having their shades drawn and candles lit during daylight hours. 1907 The scheme is proposed in earnest by UK builder and businessman William Willett, in a pamphlet entitled The Waste of Daylight. 1916 Germany becomes the first country to adopt DST, partly to conserve resources for its war effort. Britain follows suit three weeks later. The editors of Nature scornfully suggest that one might also alter thermometers to register warmer temperatures in winter. 1917 Newfoundland becomes the first North American region to adopt DST. 1948 Japan experiments with DST at the behest of the occupying Allied army. It drops the practice in 1951 and to this day is the only major developed nation without DST. 1966 The United States formally reinstates DST after experimenting with it during the Second World War. The partial success of war time had led to a disorganized system in which states even and individual counties were free to decide how and when to implement DST. 1968 Britain begins its ill-fated attempt to abandon twice-yearly clock changes and observe summer time throughout the year. The scheme collapses in 1971 under pressure from disgruntled early risers in the construction and farming industries. predict that fewer power plants will be needed for the old and the young to pursue outdoor at any one time, so less efficient ones will be activities in the evening, and benefits to busineeded less often. nesses of aligning themselves with continental The problem is, however, that the science Europe. The quality of life of nearly everyone behind the numbers remains sketchy at best. will be improved, says Tim Yeo, the member of For her calculations, Garnsey and her col- parliament who is sponsoring the UK bill. leagues compared the energy consumption Previous experiments with daylight-saving only in the weeks directly on either side of a changes have not exactly borne that out. In clock change, as the gradual shifting of the day Australia in 2000, officials experimented with length over the year makes it very difficult to an early start to DST to save energy. But energy compare annual energy use on regular time consumption in Sydney, the host city for the versus DST. And so it remains hard to say what Olympic Games that year, did not really fall the overall year-round effect would be. I don t and the change was not made permanent. think that any really exhaustive work has been And two of the largest developing coundone anywhere, Garnsey admits. In terms of tries in terms of energy India and China carbon emissions, I wouldn t say do not observe DST, even we really know yet. But in spring In spring and though they cover huge and autumn, there is quite sub- autumn, there is quite areas; China, in particular, spans four time zones yet stantial waste of electricity. substantial waste of Another main argument for has the same time across the country and all year round. pushing the clocks forward has electricity. In the United States, Conbeen the estimated lives saved from automobile accidents. Lord Sains- gress approved the shift in their DST last year. bury, the former British science minister, The clocks will be put forward in March rather has claimed that the earlier experiment, than April, then back in November rather when the country remained an hour ahead than October. The change gains Americans of Greenwich time year-round between1968 four extra weeks of DST, the first change in and 1971, saved an average of 140 lives a year. the system since 1966. Most of Canada will That adds up to nearly 5,000 needless deaths observe the same change. over the past quarter-century as a result of Meanwhile, the outcome of the British legadhering to Greenwich time in winter, says islation hangs in the balance. Yeo, the measGarnsey. That should be the deciding fac- ure s most prominent supporter, is a member tor, she says. of the opposition Conservative party, and Others point to the increased opportunity the Labour government has refused to back the idea. The issue is more about politics for popularity than sound policy, argues energy expert Mayer Hillman, emeritus fellow at the Policy Studies Institute in London. He has been calling for Britain to adopt single-double summer time since 1988. Although lighter evenings led to a drop in the number of road accidents, he notes that a popular myth persists that putting the clock forward is more dangerous, because a small spike was seen in the number of early-morning accidents after DST was introduced. I can t tell you how maddening it is, he says. And some might doubt that the precise hours of daylight really make a difference to people s behaviour anyway. A new survey of more than 21,000 Germans (T. Roenneberg, C. J. Kumar & M. Merrow Curr. Biol. 17, R44 R45; 2007) suggests that, in rural areas at least, people naturally fall into synch with the different daylight hours as they vary with geographical location, rising and going to bed with the Sun irrespective of the time shown on their watch. If the US and British proposals prove successful, then analysts can finally come closer to answering questions about the true importance of setting the clocks correctly. It may be that in the middle of winter there s not really much benefit, says Garnsey. But the reason the experiment is needed is to get the correct data. There hasn t been an extensive analysis how much energy will you save? See editorial, page 339. 345 BETTMANN/CORBIS Turning back time 1918 The United States adopts DST (see left) and divides the country into time zones. This change is made despite the protestations of Congressman Otis Wingo that while our boys are fighting in the trenches, we are here like a lot of schoolboys tinkering with the clocks . DST is dropped the following year.

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