We actually have the technological capability already, we just need to apply the resources/technology & manpower we already have into it.
The problem is that capitalism & democracy forces us to only consider the short term for a long term issue (mostly) - as I'm no fan of either the solution is actually pretty straightforward to me (as it can be).
The purpose of an economy is to service the needs of the population, if our current model is driving us into destroying our own ecosystem then I'd argue it's failed it's most basic test & requires a serious redesign.
If collectively we manage to destroy ourselves while we have the means to resolve the problems we face sitting on the shelf then maybe we don't deserve to survive as a species. (not that I believe we are looking at any doomsday style scenario) - as a species we will continue, but huge parts of the world will most likely suffer significantly more than they do already.
The problem with necessity is, it arrives significantly sooner to the poorest & most desperate parts of the world & last to those most able to shield themselves from the impact of ignoring it.
There is only really one long term solution to all the earths human made problems (climate change being just one symptom).
Population reduction.
There is no way we (as a species) can all live like the west with a population increasing, we need to make a concerted effort to reduce our population by a few billion and keep it there at a sustainable level. How we do that is the question, lots of teaching, access to birth control and greater women's rights in many countries would help. Other more draconian possibilities could include global child limits (say one child per adult - 2 per couple). That would help reduce the population. There are charities out there trying to affect the former, unfortunately they have few funds and little political power.
Reduction in population would help the other major symptoms of "humanity", extinction of species, over fishing, deforestation, pollution and water shortages, desertification and potentially wars (over resources). Unfortunately it's a difficult task and as yet no major party (outside China) have even broached the fact, probably in part because so many so called environmentalists aren't environmentalists at all, rather "humanists", only caring about how it affects humans rather than the environment as a whole.
There is only so much land we can cover in concrete, so many valleys we can flood and dam, so many deserts we can cover in solar power (which seems to be the policy of many CO2 reduction policies). If you really want to reduce your carbon footprint significantly, don't have kids*. Simple...
*gets off soapbox*
*Or alternatively, a more realistic option is to have only one or max 2 kids.