Evaporating a small percentage of ocean water into space

[starchaser137]

Could we build structures similar to space elevators that use water as a heat-carrying source and spray it into space to reduce the global temperature? Considering that we could one day have the technology to build the structure ( keeping money out of the question ), how much ocean water would we need to evaporate to reach comfortable global temperatures? And also could doing that really work? What would be the effects on ocean life?

[swansont]

Ferrying water into space is not evaporation.

You would be moving a relatively small amount of thermal energy, that won’t cool anything, at the cost of a lot of propulsion energy.

Escape velocity is ~11 km/s, so you need 1/2 v^2 of energy, minimum, to get 1 kg of mass away from the earth. Roughly 6 x 10^7 joules.

Moving a kg of water doesn’t cool anything off - no reduction in temperature. If you remove a bucket of water from a pool, the pool isn’t any cooler. It’s marginally easier to heat up for the same energy being added.

You would have to heat the water up, and at 4.18 kj/kg-C, it’s going to be a lot less than the energy cost of the propulsion.

[Danijel Gorupec]

Another problem with the idea is that Earth continuously receives energy from Sun and must release that heat to space at the same rate (to keep its temperature steady). So, if your anti-global-warming method depends on the water evaporation, you would need to evaporate water continuously... Therefore, the answer to the question "how much ocean water would we need" would be "all of it, eventually, if you don't switch to another method in the meantime".