It is vintage Bloomberg. He will even unveil an inventory of our emissions, from every belching building to every blackened bus. News stories will, no doubt, compare Bloomie to the green governor from California, though, strangely enough, it is Chicago's stodgy Richard Daley, in the fourth decade of his family's reign, who has greened his City Hall roof and is leading America's municipal pack. The media message here will be one more tweak of presidential posturing, with almost as much energy devoted to finding the right national soundbite as perfecting the right plan.

But there still are legitimate questions about just how green this springtime bloom will be. Neither Foy, nor Rohit Aggarwala, who is running the city's sustainability project, will say if the city is still committed to a goal it already agreed to—namely, cutting the city government's emissions by 20 percent by 2010. Bloomberg was one of a crowd of mayors to sign on to the 20 percent target, but Aggarwala said last week that "few, if any of the cities are set to achieve that goal," adding: "I can't tell you whether we will."

The council hasn't been much of a prod to hit the old goal either, though it once shared it. Speaker Christine Quinn, who sounds more and more like a deputy mayor, and Jim Gennaro, the usually visionary chair of the council's environmental committee, have actually become members of Bloomberg's sustainability advisory board, preferring, apparently, a share in policymaking to critical oversight. Gennaro shelved Intro 20, a bill he pushed for two years that would have mandated the 20 percent, nudged, he concedes, by the make-nice-at-all-times speaker.

He's confident the mayor's plan will do better, pointing out that the baseline for Bloomberg's PlaNYC is the present, while his bill's baseline was 1994, meaning the council proposal used a lower level of emissions as the starting point to measure the cut.

Of course, the Bloomberg goal is grander. But it's also much farther away, and largely the job of future mayors. Bloomberg will be mayor through 2009. Setting goals for 2030 is easy when you'll be long gone, and it will help the public forget about 2010 promises. Of course, there's no reason why adopting the 2030 agenda would require abandoning the more limited and immediate one, and maybe Bloomberg won't.

But the head of the mayor's Office of Environ-mental Coordination, Bob Kulikowski, testified at a Gennaro hearing last June that "current and planned measures" would only get the city to 12 percent, and that "we have more work to do over the next four years" to hit 20 percent. That suggests why Bloomie may want to wiggle out of it and sound like he's moving on up when he did. Like Aggarwala, Gennaro now concedes he has no idea if Bloomberg will even continue to think of it as a goal. That will be the test of the authenticity of whatever Bloomberg says in April.

So will changes in the 40-year-old building code. So will the actual regulatory implementation of Intro 86, a 2005 council law that puts the city's money behind its green-building mouth but has yet to take effect because of Bloomberg delays. So will green roofs, which can dramatically cut the kind of extreme heat that killed 140 New Yorkers in the August wave of 2006, an innovation that Emily Lloyd and others in the administration are championing. So will a full recognition of the need to make adapting our infrastructure and development part of "day-to-day decision-making," as the city's top climate adviser, Cynthia Rosenzweig, has urged.

To be really green, the mayor will have to have guts.

Research assistants: Adam Fleming, Matt Friedman, Dan House, Luke Jerod Kummer, Anna Lenzer, Mordechai Shinefield, Clare Trapasso, Hannah Vahl, Damien Weaver