James Hansen’s latest press conference was positively scary.

NASA’s former chief climate scientist (he recently left government to pursue a more activist role) met with environmental journalists last month at Columbia University to release a new study with the ominous title, “Assessing Dangerous Climate Change: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature.”

Hansen and his co-authors contend that the agreed-to goal of limiting global warming to 2 degrees Celsius (3.6 degrees Farenheit) above pre-Industrial levels prescribed in the recent Intergovernmental Panel on Climate Change report is still too high to prevent “long-lasting, irreversible damage” to our planet — including raising sea levels, submerging coastal cities and turning vast tracts of the earth into virtual furnaces.

Hansen departs from environmental orthodoxy, however, in arguing that there is no way to cut greenhouse gas emissions sufficiently by relying solely on green alternatives like solar and wind power.

“Suggesting that renewables will let us phase rapidly off fossil fuels in the United States, China, India, or the world as a whole” Hansen writes in an essay, “is almost the equivalent of believing in the Easter Bunny and Tooth Fairy.”

Hansen’s controversial conclusion is that we need to build a new generation of nuclear power plants. Nuclear alone, in Hansen’s view, has the potential to produce “clean” (carbon-free) electricity in the prodigious amounts that we will need it in the decades ahead.