Just as with lobbying reform, the Democrats want people to see them as the party better able to deal with national security issues, but the plain truth is that while they're not likely to be any worse than Republicans, they're not going to be any better, either.
With the U.S. in a war that is only going to get worse as we withdraw from Iraq (which doesn't necessarily mean that isn't the right decision; my own position on Iraq remains informed uncertainty), the Democrats have decided that our intelligence assets need to spend some of their limited time and assets evaluating the national security implications of global warming.
Does global warming pose a threat to national security? Quite possibly yes, but there's no way to know right now given the state of the science: we just don't know how soon changes may occur, what changes they may be, or to what extent. Those variables make all the difference in a global warming scenario, and without more information, any assessment offered about its effects on global warming will tell us more about the assumptions underlying the assessment than the real problems.
At another time, this might just be another government boondoggle, spending other people's money to benefit the cause or group of the week. But intelligence is a bit more important than studies on cow flatulence or another building named for Robert Byrd. Al Qaeda has shown a definite pattern in its attacks: it goes after targets more than once, and it seeks to up the ante with each new attack. Further, it is a patient organization. It took them eight years to launch a second attack on the WTC. Defeating those kinds of attacks requires good intelligence, and that is something the United States sorely lacks. Tossing off some of those limited assets to create a largely speculative report is little more than a concession that national security isn't really an issue for the Democratic Party.
Fortunately, both parties are blessed with the knowledge the American system doesn't hold anyone responsible for failures any longer. George Tenet walked away from his tenure as CIA director, having overseen the failure to stop the September 11 attacks and having guaranteed the presence of WMDs in Iraq, with a Presidential Medal of Freedom for his troubles. When the next attack comes, nobody is going to blame the Democrats for sending intelligence assets on a wild goose chase, nor the Republicans for launching a war than inspired who knows how many new jihadis to strike at the United States.
Isn't democracy wonderful?