Call it sinflation. The Vatican has doubled the number of mortal sins and one of them is really dirty: polluting the environment.It could be argued that one of the Original Seven Deadlies, sloth, adequately covers polluting, but clearly the Vatican wanted to issue a more precise -- and more powerful -- dictum. To the faithful, mortal sins are the worst kind there is.

Sloth, or 'acedia' for you Latin scholars, is what keeps many of us from separating trash from recyclables, from shutting off our computers/lights/engines rather than leaving them on, and from putting the brakes on what and how much we consume.

In issuing the new list of cardinal transgressions -- which threaten eternal damnation -- the Vatican takes a step further along its path to eco-friendliness.

Pope Benedict XVI, the spiritual leader of the world's 1 billion Catholics, has been increasingly vocal about his concerns over the environment. In September, dressed in bright green liturgical vestments, the Pope urged attendees of an Italian youth rally to save the planet. Last year the Vatican hosted a scientific conference on the subject of climate change. And in his Christmas homily, the pontiff addressed the global "abuse of energy" and described the planet as "ill-treated." In April he is expected to address the United Nations.

The strongest environmental message so far came over the weekend, in the form of seven "social sins," among them polluting or littering.

Setting an example on its own turf, Vatican engineers are in the process of replacing a crumbling auditorium rooftop with a solar system. The solar array will produce some 315,000 kilowatt-hours of power a year, offsetting 315 tons of carbon dioxide emissions, according to SolarWorld, its manufacturer.

SolarWorld donated and will install by this summer about 2,000 solar panels to heat and cool the auditorium. Any excess power generated by the system will be uploaded to the Vatican City grid. By planting a forest in Hungary, Vatican City is offsetting its carbon footprint, and has reportedly sealed its position as the first fully carbon-neutral state in the world.

The Vatican is making visible signs of progress in its own backyard. In other corners of the world, where there are limited means for acting in a more environmentally responsible manner, even the threat of eternal damnation may not be enough to motivate action.