Physics Colloquium

The world's critical energy problems require solutions
beyond those policy makers are exploring now. Global warming is accelerating the rate at which radical transformations of energy systems away from fossil fuels are needed to avoid "dangerous human interference with the climate system." Given the world's large -- but
climatically problematical, if CO2 is freely vented to the atmosphere -- coal resources, such a transition might be deferred to the 22 Century. But global warming is the canary in the mine. Already arctic sea ice, tundra, alpine glaciers and the Greenland Ice cap are melting; sea level is rising; tropical disease vectors carrying West Nile virus and cholera penetrate temperate latitudes; and sea surface temperatures have warmed to the point where intense hurricanes like Katrina are not only more probable; but happen. These impacts will only worsen under "business as usual." What to do? To prevent > 2 degree Celsius warming, above which disintegration of the Greenland Ice Sheet and West Antarctic Ice sheets may become irreversible, as
global GDP continues growing 2-3%/yr, carbon cycle and climate models indicate that 100-300% of human primary power consumed today must come from some combination of non-CO2 emitting energy sources and "negawatts" of demand reduction from by midcentury. No "silver bullet" or combination of bullets on the shelf will easily solve this
problem. But technological options exist in principle that could work with prompt and massive R & D and scale-up: (1) coal gasification combined cycle power plants producing electricity and fuel cell grade hydrogen with CO2 sequestered underground, (2) new generations of
operationally safe, proliferation-resistant and waste-managed nuclear reactors burning fuel bred from U-238 and thorium (and eventually fusion) and (3) renewable energy, primarily solar and wind, with innovative transmission and storage technologies deployed at the global scale (including, space-based