But now Cool Earth Solar of Livermore, California, has come up with what it hopes will be a better, cheaper alternative: balloons.
In summer the reverse process takes place: The (comparatively) cool earth becomes a waste dump for unwanted heat that accumulates inside the house.
At low altitudes they help to cool the Earth by reflecting sunlight away from it.
So they would cool the Earth by hanging around and by reflecting more heat from the sun back into space.
The "white parasol" at the top of the planet reflects energy from the Sun straight back out into space, helping to cool the Earth.
Exhaust gases from shipping already brighten clouds over various bits of the ocean, and in so doing are thought to cool the Earth appreciably.
Recently, the scientific entrepreneur Nathan Myhrvold, whose company Intellectual Ventures has invested in several geoengineering ideas, said that we could cool the earth by stirring the seas.
Attended by marching bands and flags and encouraged by a district mayor, the good burghers of several streets were painting their roofs white, to reflect sunlight and cool the Earth.
Regardless of which theory is correct (and both might be wrong), the effect of fewer cosmic rays would be fewer clouds and since clouds tend to cool the earth by reflecting incoming solar radiation away from it a warmer planet.
And the nuclear-winter hypothesis (that the smoke from fires caused by a global nuclear war would blot out the sun's rays and thus cool the earth catastrophically) owes its origin, at least in part, to observations of a planet-wide dust storm on Mars.
Ken Caldeira of Stanford University, another of the authors, reckons that it may be feasible to place sulphates in the stratosphere near the poles and thus cool the Earth in a place where global warming manifests itself most strongly, though that would scarcely please the Russians and the Canadians.
Injecting sulphate particles into the stratosphere, for instance, would cool the Earth by reflecting more sunlight into space. (Nature has already shown that this concept can work, since volcanic eruptions that send sulphur-rich plumes into the stratosphere can temporarily alter the world's climate.) However, Dr Lenton notes that the method becomes less effective as the atmosphere becomes more saturated with particles.
Nearly a century ago, the British scientist John Tyndall suggested that a fall in the atmospheric carbon dioxide could allow the earth to cool whereas a rise in the carbon dioxide would make it warmer.
We will wash water, and warm fire, and cool ice, and underprop the earth.
Kimberlites have the deepest origins of all magmas on Earth and when they cool, they leave behind rocks dense in crystals, sometimes holding diamonds.
That has prompted some to speculate that the Earth may be entering another cool period that could offset the warming caused by greenhouse gases trapping heat in the planet's atmosphere.
"Welcome to the greatest music show on earth, " said rapper LL Cool J at the beginning of the evening in his role as ceremony host.
The good optimism springs from what Silicon Valley does better than anyplace else on Earth: It turns technology into cool products and wraps dynamic companies around them.
Even if I wasn't as cool and thoughtful as I hoped to appear, the first Earth Day's message was good then, and it's better today: We have to take care of the Earth.
Under the studio lights, he can seem with his spectral white hair, pallid skin, cool eyes, and expansive forehead like a rail-thin being who has rocketed to Earth to deliver humanity some hidden truth.
应用推荐