If the solar system has an underachiever, it has to be Venus. The planet is about the same size as Earth; it sits closer to the sun than we do, but not by much — 67 million miles, compared with 93 million miles (or 108 million km vs. 150 million km). Its year, at 243 days, is not even all that different from our standard 365-day model. The big distinction is the temperature. A hot day on Earth is perhaps 85°F (30°C); a simply average day on Venus is 800°F (427°C). That's a little too toasty for life — at least as we know it. But if new European Space Agency (ESA) findings from the Venus Express spacecraft are correct, it looks as if Venus coulda been a contender. The reason: it once had water.
The relatively small distance that separates Venus' and Earth's proximity to the sun makes a very big difference in temperature. Light falls off exponentially with distance, so a planet that is, say, twice as close to the sun as Earth is would get much more than twice the solar energy.
Making problems much worse for Venus, its atmosphere is a thermal quilt, 93 times denser than Earth's and made up mostly of carbon dioxide and sulfur dioxide. That leads to a runaway greenhouse effect — and that, in turn, makes it awfully hard to hold on to the oceans and seas that served as the incubators for all terrestrial life. If you could collect all of the water on Earth and distribute it evenly around the planet, it would make a global ocean 1.9 miles (3 km) deep. Do the same with the trace amounts of water in the Venusian atmosphere, and the depth of your ocean would be just 1.8 in. (3 cm).
http://www.time.com/time/health/article/0,8599,1999792,00.html Quote:What you actually mean is " without any thermostatic switch that we know of"
The switch is 'changing human behaviour'.
And Venus' past shows enough evidence, that those opposed to conscious geo-engineering, rather their continual path of unconscious geo-engineering of the planet, are risking all life on this planet.
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