It is too late to “prevent global warming;” the current cycle has been in progress for some time. The concern is that unless action is taken now to reduce the rate at which the atmospheric temperature is rising, eventually no possible intervention could suffice to prevent a global catastrophe. The concern arises from the fact that the atmospheric conditions are known to evolve in a nonlinear fashion (e.g., The Butterfly effect).
We aren’t taking any steps to cool the planet. We are attempting to minimise the warming effect of CO2 emissions. Even if we were 100% successful world temperatures would just stay the same, they wouldn’t decrease.
No, of course not. The premise of “doing to much” is not realistic. We’re not doing enough and the political climate in the US (to say nothing about the rest of the world) is simply not going to get us into a situation of doing to much.
I have little doubt that civilization has had a significant impact on the planet, especially the use of petrochemicals and the effects of mining in the last few centuries. Unless we develop more effective ways of dealing with byproducts of agriculture and technology, climate change may be the least of our worries.