In the August 13th issue of Science, Stephen Pacala and Robert Socolow of Princeton's Carbon Mitigation Initiative published a paper identifying 15 existing technologies that could each prevent 1 billion tons a year worth of carbon emissions by 2054. Pacala and Socolow have created a graph that divides the problem into the seven 1 billion-ton-per-year "wedges" which are required to halt the rise in greenhouse gas emissions, and stabilize the concentration of carbon dioxide in the atmosphere at 500 parts per million (ppm) (see figures in full document).

Their findings provide a strong counter to the argument that major new technologies need to be developed before significant mitigation of emissions can begin.

I strongly reccomend that you read the full document HERE