Reply #11: Our benifits to earth lie in the distant future

[Odin2005]

Various things dealing with nuclear reactions and the gas laws cause the Sun's core to slowly become more dense ( and therfore causing the rate of fusion to increase) as more hydrogen is converted to helium, this causes the sun to slowly get brighter over billions of years. 4 billion years ago the sun was 30% dimmer, requiring Earth to have lots of atmospheric CO2 to keep warm. as the sun brightened warming caused increased rainfall and therefore erosion, which caused more CO2 to be trapped as limestone in the oceans, this feedback loop has generally kept the earth's average temperature between 12C and 22C.

Now, the ever brightening sun is casing the Earth is starting to run low on CO2 (the current human-caused mess will correct itself in a couple million years one we've stoped using fossil fuels, and so is insignificant on the timescales I'm talking about). 500 million years from now the CO2 levels will reach the minimum level that photosynthesis can occur (40ppm). If the level drops below the minimum plants will begin to die on a massive scale, the rotting releasing CO2 back into the atmosphere; the feedback loop keeping the earth mild will go haywire and Earth will eventually the ever-brightening sun will cause the oceans to start boiling way, and Earth will become a new Venus.

This is where inteligent life can help. in the distant future when we are super-advanced we could slowly move the Earth outward as the sun brightens, or even sooner put up a "sunshade" allowing us to control the amount of light comming in. This could allow us to keep the Earth alive untill the Sun dies.