I've written several Hubs on the history of global warming science, as well as reviewing contemporary books on the topic (check out my profile to have a look at any of these.) Studying that history leads me to believe that humanity has a real problem on its collective hands.
What should we do? Implement an effective international agreement to reduce emissions; implement national, regional and local policies to reduce emissions; take what steps we can individually to reduce emissions.
I think such a plan will necessarily involve a mix of carbon-free energy sources, wind, solar, geothermal, nuclear, biofuel--as well as novel energy storage methods--better batteries, flywheel energy storage such as that being pioneered by Beacon Energy, pumped hydro and more.
It will involve changing our economic framework in such a way that there is a cost associated with carbon pollution; now the atmosphere is a trash dump with no tipping fee.
It will involve changing our lifestyles to some degree, in all likelihood--not just a simple "doing without," as some like to caricature it, but definitely a "doing smarter."
And it may also involve active carbon sequestration--by burying biochar (aka "terra preta"), by accelerated reaction with olivine or similar minerals, or by technological methods such as the "Lackner trees" now under commercial development by Kilimanjaro Energy.
The problem is that we're already behind the eight-ball; we just don't know it yet as a society. Many are convinced that the atmospheric concentration of CO2 should not be allowed to exceed 350 parts per million (ppm) for an extended time, and we're already at around 390, and rising at about 2 ppm per year. It will be a struggle, based on current trends, to keep it below 450. So the ability to draw down CO2 concentrations would seem to be crucial.