I saw this referenced on digg. Thought it was kind of interesting. I didn't know PHP was that slow, but you have to read some of the comments to see a lot of argument.
In the USA, an average of 560 grams CO2 is emitted per generated Killo Watt hour.
Here's the real problem.
Of course it's important to be energy efficient, but that's utterly secondary. Reusable energy sources, or nuclear power, have zero emission.
It's not enough to reduce CO2 emission by a few percent. The source of the issue has never been energy consumption, but releasing CO2 into the atmosphere by burning fossil fuel.
Oh yeah, most of these discussions are a little flaky, and I'm not entirely convinced it's as bad as they say. We went through this with Y2K and everything. It's always something imminently terrible is going to happen any second but these changes are very gradual and a little warming probably isn't that bad considering we're sitting between ice ages. We're going to run out of fossil fuels in a bit anyway and they will continue to become more expensive so alternatives will be found. Fusion will be best if they can work it out. Some countries are dumping nuclear waste in the ocean right now and it has a half life of what, 4 billion years or something? Man alive, that's way more dangerous. Chernobyl came just a little from wiping out a huge percent of the population. It's the snake you don't see that bites you.
I just didn't know that PHP was 10 times slower, but I think, like the discussions, there are a lot of factors involved. Like how much of it actually gets used. These languages are meant only as a glue for c code.