Most scientists know and acknowledge these uncertainties, and reason as follows. We're in an unprecedented situation, with regard to the concentration of CO2 in the atmosphere and the rate at which it is rising. Because this is unprecedented, we are not sure what is going to happen. But global warming is very likely, and reasonably probable outcomes could be fatal. Ignoring it would be like Russian roulette. Want to play?.... (here, via AS)Data here. Photo here.