Bob Murphy's critique of Nordhaus is up at IER. Nordhaus's original piece from the Spring is here.
By the way, Krugman was Nordhaus's RA at Yale as an undergrad.
Daniel Kuehn is a doctoral candidate in economics at American University. He has a master's degree in public policy from George Washington University.
Evan, his brother, occasionally blogs on F&OST, but can usually be found here.