Obama's looking for a new foreign-policy adviser, and he could do far worse than Columbia's superstar economist, that rare critic of the Bush administration and the global power structure who deigns to offer actual solutions. His latest, eminently accessible volume describes exactly how an outlay of 3 percent of global income can curb global warming, world poverty, and population growth for generations to come. Then, of course, comes the hard part — creating the political will to aim for multilateral solutions.