This is the charge made by Arnold Kling at econlog and in more detail by Andrew Biggs. Biggs is former Bush hit man on social security, and he and Kling both see those who doubt that social security is "in crisis" and those who doubt that global warming "is a problem" as being somehow similar, namely confused, and if one is supporting one and not the other, not just confused, then (implicitly, although neither used this word) hypocritical.
I have commented on Biggs's blog that I think it is not unreasonable to support social security as is while supporting doing something about global warming. He claims that changes to social security are "permanent" (as are changes to global climate), and of course supports the usual pessimistic forecasts. I argue that on social security that a) the pessimistic forecasts have not done too well so far, and b) social security can be changed at any time if indeed things go bad. However, with global warming, the downside is much worse and the lead times are much longer. Also, they do not have the same probability distributions, with social security essentially more of a normal distribution, but with global warming, as Martin Weitzman has pointed out (and similar to financial market returns), there are these non-normal "fat tails," too high a chance of extreme events due to nonlinearities and positive feedbacks in the system, with the geological record supporting the idea that very rapid temperature change has happened in the past. So, we must worry about those non-trivial catastrophic outcome possibilities, much more serious than possible underfunding of the US social security system.