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NEWS NATURE|Vol 448|5 July 2007 No solar hiding place for greenhouse sceptics A study has confirmed that there are no wood brought together solar data for the past grounds to blame the Sun for recent global 100 years. The two researchers averaged out warming. The analysis shows that global the 11-year solar cycles and looked for correla- warming since 1985 has been caused nei- tion between solar variation and global mean ther by an increase in solar radiation nor by temperatures. Solar activity peaked between a decrease in the flux of galactic cosmic rays 1985 and 1987. Since then, trends in solar irra- (M. Lockwood and C. Fröhlich Proc. R. Soc. diance, sunspot number and cosmic-ray inten- A doi:10.1098/rspa.2007.1880; 2007). Some sity have all been in the opposite direction to researchers had suggested that the latter might that required to explain global warming. influence global warming through an involve- In 1997, Henrik Svensmark, a physicist at the ment in cloud formation. Danish National Space Center in Copenhagen, “This paper is the final nail in the coffin suggested that cosmic rays facilitate cloud for- for people who would like to make the Sun mation by seeding the atmosphere with trails of responsible for present global warming,” says ions that can help water droplets form (H. Sven- Hot topic: solar activity peaked too early to have Stefan Rahmstorf, a climate scientist at the smark and E. J. Friis-Christensen J. Atmos. caused the current trends in climate change. Potsdam Institute for Climate Impact Research Solar-Terrest. Phys. 59, 1225–1232; 1997). He in Germany. proposed that, as a result of this, changes in the a Sun–climate link, argues that there may be a Claims that the Sun, rather than raised lev- Sun’s magnetic field that influence the flux of lag in Earth’s reaction to the Sun because of the els of greenhouse gases, has been responsible cosmic rays could affect Earth’s climate. This led thermal inertia of the oceans. for recent warming have persisted in a small to claims that cosmic rays are the main influ- But other climate researchers find the idea of number of scientists and in parts of the media. ence on modern climate change. a ‘hidden’ time lag unconvincing. “With each Mike Lockwood, a physicist at the Rutherford Even in the face of the new analysis, Sven- year, and with each new set of data that comes Appleton Laboratory in Chilton, UK, says he smark insists that solar theories should not be in, a time lag becomes ever more unlikely,” says was “galvanized” to carry out the comprehen- dismissed. “If you look at temperatures in the Urs Neu, deputy head of ProClim-, the climate sive study by misleading media reports. He troposphere, there is a remarkable correlation and global change forum of the Swiss Academy cites ‘The Great Global Warming Swindle’, a with solar activity,” he says. Lockwood insists of Sciences in Bern. television programme shown in March by Brit- that none of the tropospheric data show the On other timescales, however, Sun–climate ain’s Channel 4, as a prime example. trend that the solar theory would need. links may remain worthy of study. “Climate Together with Claus Fröhlich of the World Nir Shaviv, an astrophysicist at the Hebrew change is a cocktail of many effects,” says Jas- Radiation Center in Davos, Switzerland, Lock- University of Jerusalem who has championed per Kirkby, a physicist at CERN, the European Cosmic-ray results auger well for future The first substantial results from highest-energy particles be slowed down by interactions the world’s largest detector of bombarding Earth from with the cosmic microwave cosmic rays are being presented space. background as they travel. Cosmic this week at a conference in Among the results rays significantly above the cut- Mexico. being presented at the off energies would thus have The Pierre Auger Cosmic Ray International Cosmic Ray to come from relatively nearby, Observatory is already the largest Conference in Merída, which would imply that they were cosmic-ray observatory in the Yucatán on 3–11 July are produced by strange new physics, world even though it is only three- new measurements of the such as the spontaneous decay of quarters finished. It sprawls across energy spectrum of cosmic unknown massive particles. more than 3,000 square kilometres rays. The team confirms An experiment in Japan called of the Argentine pampas near A small component of a large observatory. that above a threshold the Akeno Giant Air Shower Array the city of Malargüe — an area energy known as the GZK sparked excitement when it failed a tenth the size of Belgium. detectors and 24 telescopes have cut-off the number of cosmic-ray to see the cut-off in data obtained Researchers from the 15 countries been commissioned around the events falls sharply. Particles up to 2004. Since then, though, collaborating on the US$50-million end of this year the observatory that start off with energies above data from the High Resolution Fly’s project hope that after its 1,600 may reveal the origins of the this threshold are expected to Eye — a detector in Utah — have 8 NATURE|Vol 448|5 July 2007 NEWS ASTEROID MISSION GEARS UP FOR LAUNCH NASA mission leaders hope Dawn will rise on time. www.nature.com/news The great gig in the South When Al Gore and his colleagues the performance will be recorded ‘as live’ a dreamed up the idea of a climate-change day or so beforehand. “We’re effectively e- consciousness-raising Live Earth event mailing it in,” says Balmer. featuring concerts on every continent, they Despite the technical delay, the came up against a problem. The event’s performance should be pretty authentic. 7 July date corresponds with midwinter in The band plans to perform outside the Antarctic, when no one gets on or off — which might make their instruments the seventh continent. So flying in Bono “sound a bit funny”, according to the BAS’s and Madonna to frolic with penguins Linda Capper, back in balmy Cambridge, would not be an option. UK, not withstanding the rigours faced by Enter Nunatak, a five-strong band of the performers. guitar, bass, drums, fiddle and sax, whose Balmer is tough enough to dismiss such members are part of the crew at the Rothera worries: “It’s only minus six outside; you Research Station, run by the British get used to these sorts of temperatures.” Antarctic Survey (BAS). Nor does the prospect of a It is not the only band on “They will be throwing global audience chill him, W. BURGESS/REUTERS W. the continent. Every New their underwear.” in part because it doesn’t particle-physics laboratory near Geneva in Year’s Day, the US McMurdo feel that real. “We don’t Switzerland, who is leading an experiment base hosts the Icestock festival, and even in have an appreciation of it,” says Balmer. aimed at simulating the effect of cosmic rays on winter there’s plenty of music. “All the bases “We see the world through the Internet.” clouds. “Past climate changes have clearly been have bands except maybe Bird Island, as The last ship out of Rothera left in April. associated with solar activity. Even if this is not there are only four overwintering people “Until October we won’t see anybody else.” the case now, it is still important to understand there,” explains Julius Rix at the BAS’s Saxophonist and marine biologist Alison how solar variability affects climate.” more southerly Halley base. But being the Massey expects the rest of the base to be an Ken Carslaw, an atmospheric scientist at the farthest north of the bigger bases gives appreciative audience, not least because University of Leeds, UK, points out that solar Nunatak an advantage. “Rothera has double after weeks of rehearsal at close quarters, effects might still be possible. They might have the satellite bandwidth compared to us,” “it will be the last time they’ll hear the acted to cool the climate in recent decades, but says Rix. And so Nunatak got the gig. songs”. Balmer hopes for something a bit been overwhelmed. If so, the climate could Even so, the webcam set-up on Rothera more rock and roll: “There will probably be more sensitive to greenhouse gases than isn’t quite up to sending broadcast-quality be groupies throwing their underwear at is generally thought, and future temperature sound and visuals live to the world. “To do it us,” he says. With only 17 people in the increases might be greater than expected if a live we would need a very fast satellite link,” audience, though, matching the knickers to countervailing solar effect comes to an end. ■ says Matt Balmer, an electronics engineer the punters may not be too hard. ■ Quirin Schiermeier and Nunatak’s guitarist and songwriter. So Katharine Sanderson provided evidence for the reality of the cut-off. The new Pierre Auger data seem to confirm that the cut-off is real. If there is no new physics in the form of particle decays or other exotic effects, though, SURVEY BRITISH ANTARCTIC there should be plenty of new astrophysics in understanding what sort of celestial mechanism might be pumping up incoming protons to energies millions of times higher than those produced by the most powerful Earth-based accelerators. One crucial step is to identify where in the sky they are coming from. Alan Watson of the University of Leeds, UK, a spokesman for the Pierre Auger project, says that the team has identified some interesting candidate regions of the sky, but won’t reveal the details until it has obtained more data.

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