Preposterous Guru

For the past seven years, this German set-up has been looking for gravitational waves - ripples in space-time thrown off by super-dense astronomical objects such as neutron stars and black holes. GEO600 has not detected any gravitational waves so far, but it might inadvertently have made the most important discovery in physics for half a century.

For many months, the GEO600 team-members had been scratching their heads over inexplicable noise that is plaguing their giant detector. Then, out of the blue, a researcher approached them with an explanation. In fact, he had even predicted the noise before he knew they were detecting it. According to Craig Hogan, a physicist at the Fermilab particle physics lab in Batavia, Illinois, GEO600 has stumbled upon the fundamental limit of space-time - the point where space-time stops behaving like the smooth continuum Einstein described and instead dissolves into "grains", just as a newspaper photograph dissolves into dots as you zoom in. "It looks like GEO600 is being buffeted by the microscopic quantum convulsions of space-time," says Hogan.

If this doesn't blow your socks off, then Hogan, who has just been appointed director of Fermilab's Center for Particle Astrophysics, has an even bigger shock in store: "If the GEO600 result is what I suspect it is, then we are all living in a giant cosmic hologram."

The holograms you find on credit cards and banknotes are etched on two-dimensional plastic films. When light bounces off them, it recreates the appearance of a 3D image. In the 1990s physicists Leonard Susskind and Nobel prizewinner Gerard 't Hooft suggested that the same principle might apply to the universe as a whole. Our everyday experience might itself be a holographic projection of physical processes that take place on a distant, 2D surface.

Such a situation would not be unprecedented in physics. Giant detectors built to look for a hypothetical form of radioactivity in which protons decay never found such a thing. Instead, they discovered that neutrinos can change from one type into another - arguably more important because it could tell us how the universe came to be filled with matter and not antimatter (New Scientist, 12 April 2008, p 26).

It would be ironic if an instrument built to detect something as vast as astrophysical sources of gravitational waves inadvertently detected the minuscule graininess of space-time. "Speaking as a fundamental physicist, I see discovering holographic noise as far more interesting," says Hogan.

The research, led by one of the world's top climate scientists, suggests that almost one-third of the global warming recorded during the 1990s was due to an increase in water vapour in the high atmosphere, not human emissions of greenhouse gases. A subsequent decline in water vapour after 2000 could explain a recent slowdown in global temperature rise, the scientists add.

The experts say their research does not undermine the scientific consensus that emissions of greenhouse gases from human activity drive global warming, but they call for "closer examination" of the way climate computer models consider water vapour.

Satellite measurements were used to show that water vapour levels in the stratosphere have dropped about 10% since 2000. When the scientists fed this change into a climate model, they found it could have reduced, by about 25% over the last decade, the amount of warming expected to be caused by carbon dioxide and other greenhouse gases.

They conclude: "The decline in stratospheric water vapour after 2000 should be expected to have significantly contributed to the flattening of the global warming trend in the last decade."

They fear the warming caused by increased methane emissions will itself release yet more methane and lock the region into a destructive cycle that forces temperatures to rise faster than predicted.

Palmer said: "This study does not show the Arctic has passed a tipping point, but it should open people's eyes. It shows there is a positive feedback and that higher temperatures bring higher emissions and faster warming."

Those happy souls you see dancing through the icicles? They're the ones who believe that humans are now off the hook for climate change, even as greenhouse gases continue to accumulate in our air. Cowering in the corner is another group: those who fear that Greenland's melting ice sheets are already starting to pinch off the Atlantic's warm conveyor belt, a hypothesis explored most luridly in the film The Day After Tomorrow. In real life, any such slowdown would be expected to unfold in decades rather than weeks.

Rather than seeking vindication or catastrophe in this cold snap, now is a good time to remind ourselves that weather, like death and taxes, will always be with us. Spectacular regional swings in temperature and precipitation, sometimes lasting for months, often emerge from the natural jostlings of atmosphere and ocean. By themselves, none of these prove or disprove a human role in climate change.

In any given year, we could find ourselves in a season as shocking as Britain's epic winter of 1962-63 - when snowdrifts were measured in metres, and temperatures stayed below freezing for most of January - or the summer of 2003, when tens of thousands died in some of the worst heat ever recorded in Europe.

If you're craving a scapegoat for this winter, consider the Arctic oscillation. The AO is a measure of north-south differences in air pressure between the northern midlatitudes and polar regions. When the AO is positive, pressures are unusually high to the south and low to the north. This helps shuttle weather systems quickly across the Atlantic, often bringing warm, wet conditions to Europe. In the past month, however, the AO has dipped to astoundingly low levels - among the lowest observed in the past 60 years. This has gummed up the hemisphere's usual west-to-east flow with huge "blocking highs" that route frigid air southward.

Handy as it is, the AO describes more than it explains. Forecasters still don't know exactly what sends the AO into one mode or the other, just as the birth of an El Niño is easier to spot than to predict.

What we do know with crystal clarity is that the atmosphere's load of greenhouse gases is increasing by more than 10 million tonnes every year. The tepid agreements out of Copenhagen are unlikely to change that trend anytime soon.

If this winter tells us anything, it's that we'll have to remain on guard for familiar weather risks as well as the evolving ones brought by climate change. Juggling all of these at once will not be an easy task.

In a series of coordinated announcements at several US laboratories, researchers said they believed they had captured dark matter in a defunct iron ore mine half a mile underground. The claim, if confirmed next year, will rank as one the most spectacular discoveries in physics in the past century.

Tantalising glimpses of dark matter particles were picked up by highly sensitive detectors at the bottom of the Soudan mine in Minnesota, the scientists said.

Dan Bauer, head of the Cryogenic Dark Matter Search (CDMS), said the group had spotted two particles with all the expected characteristics of dark matter. There is a one in four chance that the result is due to some other effect in the underground detectors, Bauer told a seminar at the Fermi National Accelerator Laboratory, near Chicago.

Rumours that Bauer's group was on the verge of making an announcement surfaced on physicists' blogs a few weeks ago. Though tentative, tonight's results triggered an immediate wave of excitement in the science community.

"If they have a real signal, it's a seriously big deal. The scale on which people are looking for dark matter is vast," said Gerry Gilmore at Cambridge University's institute of astronomy. "Dark matter is what created the structure of the universe and is essentially what holds it together. When ordinary matter falls into lumps of dark matter it turns into galaxies, stars, planets and people. Without it, we wouldn't be here," Gilmore said.

"People do not quite realise the scale of the issue," added Bevan. "This is one of the most serious problems that science has ever faced." In Britain the lives of hundreds of thousands of people will be threatened by food shortages. Across the globe, tens of millions - if not hundreds of millions - will be affected.

A guide to the amount of light given by a CFL bulb is given on its box as a comparison to the wattage of an incandescent bulb. But the European Commission says in a FAQ document this can be misleading.