I'm a climate scientist. I got to meet Will.i.am on Monday (apologies for the name-drop, but my daughter assures me that he is definitely the safest person a university professor is every likely to meet). He arrived in a helicopter. Lots of sanctimonious journalists then got upset about his carbon footprint.
Which gives me an opportunity to explain why nagging people about their carbon footprint, or worrying about your own, is essentially irrelevant to the issue of climate change. Worse, guilt-tripping individuals provides a handy distraction from our failure to make any progress at all on the measures actually necessary to solve the problem.
Carbon emissions from fossil fuel use and deforestation are currently approaching 300 tonnes per second: check trillionthtonne.org to see what this means. And once it is out there, it accumulates. So the brutal truth is that just burning carbon slower doesn't help: Will.i.am forgoing his helicopter for the train via Reading would have saved the world from global warming for less than a millisecond.
Even if you were, heroically, to reduce your personal carbon footprint to zero for the rest of your lifetime, you would only buy the rest of us a second or two before accumulated carbon emissions were exactly back to where they would have been without your efforts.
"Yes, but if we all were to join in …" the environmentalists reply, betraying a fundamental disconnect with the way free markets work. When a resource is as useful as fossil energy, individual abstinence is not a way to reduce overall consumption. Even if Europe as a whole were ever actually to reduce consumption with a cap-and-trade scheme, reduced demand would depress fossil fuel prices, and consumption would bounce up elsewhere.
"So we need a global cap-and-trade regime …" – but beware what you wish for. Because carbon accumulates in the atmosphere, we aren't going to stop global warming until the net flow of fossil carbon out of the ground is virtually zero. Claiming you can do this with a global emission cap means you believe that someone, someday in the not-too-distant future, will have the power to regulate and ultimately ban every human activity that involves the burning of fossil fuels