One single, average human weighs somewhere around 65kg. So, not counting the mass of the fuel and vehicle necessary to do so, evacuating one human costs the energy equivalent of around 1820kWh of electricity. The average American household uses just over 10000kWh per year [1], just for comparison.
Now, let's get to the bad news. Remember the weight of the vehicle and fuel that we just conveniently forgot about? Let's not forget about it anymore.
Falcon 9 weighs around 550,000 kg [2]. So, just to put it in orbit, empty, costs the equivalent of over 1.5x10^6 kWh of electricity, or, roughly the yearly consumption of 1500 years worth of the average American household's energy consumption. That energy has to come from somewhere.
Tell me, how is space going to save us again?
On the other end, in less than 20 years, we need to not only offset the trend of 50% increase in global energy consumption, but also cut back an additional 50% from where we are today. In other words, in 20 years, in order to simply break even in terms of sustainability, we need to become 3x more efficient than we ever have over any 20 year period, if we want to maintain current levels of economic growth.
And you don't find that hard to imagine?
Edit: Alternatively, do you see us supporting 2 billion more people on this planet in 2050 with lower levels of economic growth than we've had the past few decades?
See https://en.wikipedia.org/wiki/Projections_of_population_grow... for population growth estimates.
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[0]: https://space.stackexchange.com/questions/4330/how-much-ener...
Wouldn't the general idea be to put things like solar cells into space, to increase the amount of harvestable energy we can use, not humans?
Very long-term projects like space elevators, mass drivers etc. can help reduce the amount of energy (from Earth) that is required to efficiently launch something.
But, what I think you're saying is that if we can increase efficiency by X%, then we can still sustain current economic output, yes? Well, considering we're 70% over the sustainable level, that means we'd need to get 58% more efficient, with no increase in consumption, in less than 20 years.
How likely do you think that is?
Our current energy needs could be harvested from the sun exclusively. Cover sahara in solar collection and you satisfying energy requirements of all of humanity, several times over.