There are two main issues at stake in the Keystone XL decision: path dependency and US leadership. Path dependency is the term use to describe the fact that once a policy is put into place, it then constrains future options to those within that policy framework. More simply, the choices we make now determine what choices we get to make in the future.
A classic example is the "qwerty" keyboard layout. Even though this layout may not be the most efficient, it was the first one, and so it became the standard. New keyboard layouts would have to compete with an established format, meaning consumers would have to adapt to a new system they had no experience with. On the basis solely of legacy, inferior standards or policies remain in place, more or less out of inertia.Given that Professor Mann is suing columnist Mark Steyn over false claims, it is rather astonishing that he would assert a claim that was debunked by the economists Stan Liebowitz and Steve Margolis over a quarter century ago. As has been documented numerous times at HSIB.
At least Paul Krugman actually is a Nobel laureate.