In the past global warming through natural means such as solar activity has caused melting ice and warming seas to release stores of CO2 which then accentuate the effects of the global warming, this causes the lag between temperatures and CO2 levels in past instances.
However this time around the CO2 levels are rising before the global temperatures as the CO2 is being released by an entirely different mechanism - the burning of fuels. Climate change models, run by people a lot smarter than me on very expensive super computers, all show that the effect of the increased amount of CO2 in the atmosphere will cause and is currently causing another instance of rising global temperatures.
The best way to combat this is to lower the amount of CO2 released into the atmosphere and the best way to do that is to find alternate fuel sources. There are many plausible fuel sources; wind, wave, tide, solar, nuclear, geothermal, biofuel. Of these there are a few which are unable to generate a significant enough amount of energy. Geothermal is limited to geothermal areas and biofuels cause food shortages. However the rest are renewable (except nuclear but a near unlimited resource can be considered renewable) and able to supply the human race without CO2 emissions.
The best technique in my opinion would be either fusion reactors or mirror fields in the Sahara desert.
Edit: @post above me. Solar power can be used if you either use certain types of liquid in the towers which retain heat or if you store the energy. An interesting way of storing energy is to use the energy to pump air into certain types of rock and when you need the energy again to use the stored pressure to drive generators. Not entirely efficient but it would probably work.
