Hansen is now famous in the world of climate studies, and infamous to the world of the right wing, but back then he was a 40-year-old researcher who came up with a projection of how rising CO2 levels might affect global temperatures. Science lives for the "falsifiable hypothesis" -- a claim that can be tested against the evidence -- and that is what the paper by Hansen and his colleagues offered up. Three decades later, his worst-case projections were matched against what has happened since then. You should read their full findings, but this gives you the idea:
