If you asked most people where they choose to exercise, they would surely tell you they run or bike or Zumba, if they can carve out the time, somewhere close to home or work, perhaps on a treadmill, in the basement. Since the beginning of his mayoralty, though, Bill de Blasio, forsaking convenience for familiarity, has instead elected to be driven 11 miles, from Gracie Mansion in Manhattan to a Y.M.C.A. branch in Park Slope, Brooklyn, a few blocks from where he used to live. The trip, made on many weekdays, typically requires two S.U.V.s, except on the occasions when he is joined by his wife, Chirlane McCray, in which case it often takes three.

While this routine had been written off as an indulgent peculiarity, from a politician who manages to embody all of the arrogance of a corporate chief executive with little of the efficiency, it has recently left the mayor fighting off charges of hypocrisy, at a time when he has asked New Yorkers themselves to take on more individual responsibility to combat climate change. During a regularly scheduled radio appearance on WNYC recently, Mayor de Blasio implied that he would not be baited into the “cheap symbolism’’ of taking mass transit to the gym, and that caravan-style mobility was, in effect, his right. His life, he maintained, was not like, “everyone else’s,” a claim that assumes we have forgotten that he ran in opposition to the image of his plutocratic predecessor, Mayor Michael R. Bloomberg, as a man of ordinary habits, like any other you might encounter on the R train.

Leaving aside whether or not it is “cheap symbolism” for the mayor of the country’s largest city to ride the subway, at a moment when the system itself is so distressed, Mr. de Blasio has hardly seemed resistant to fits of shallow posturing in the past. During his 2013 mayoral bid, for example, he engaged in ostentatious acts of protest against the prospective closing of Long Island College Hospital in Cobble Hill, Brooklyn — getting arrested and availing himself of the media exposure that comes with handcuffs — only to drop his support for a full-service hospital when he won, and back a plan for residential towers on the site.

Just how damaging are the mayor’s fitness proclivities? According to Charles Komanoff, an energy analyst and founder of the Carbon Tax Center, who phoned in last week to suggest the mayor seek alternative transportation, his one-way trip from Gracie Mansion to Park Slope releases approximately 12 pounds of carbon into the atmosphere. There are 2 million registered vehicles in New York City; what if every one of them were dispatched once a day to take a superfluous ride to a recreational facility over 10 miles away?