Conclusions, based on the Copenhagen promises about 2020:
This doesn't mean I won't stop trying to slow anthropogenic climate change. But from this point forward all major planning exercises should include a worst case scenario for global warming. For instance, with respect to HSR, route selection should consider a ten foot (three meter) sea level rise and a 50% increase in the maximum predicted storm surge. The new design assumptions wouldn't affect just projects on the Gulf Coast and in Florida; there are also extensive low-lying areas in the San Francisco and NYC regions. Something that will have to be considered everywhere is water, as much of the US will become drier. Of course, there is always a chance that new technologies will come along in time to save us. There is also the chance that humans will fully grok the problem in time to change, but it's much smaller. The political and cultural dynamics at play are don't give me much hope.
Update 2009/12/16: Sites expected to be in use or toxic for more than 200 years should take into account a full 33 foot (9 meter) rise.