The whole "fault" meme is Garden of Eden bullshit, the implication being that we need to busy ourselves—pronto—with barfing up the forbidden apple.
To get a good chance of staying below 2C, the report's scenarios show that world emissions would have to fall by between 40 and 70 percent by 2050 from current levels and to 'near zero or below in 2100.
This forecast has about a 5% chance of being vindicated retrospectively by future generations of scientists as being mostly on the mark. Isn't it amazing how it comfortably falls within the parameters—as tuned by the 2C free parameter—of what might fly politically (if we really did busy barfing up the forbidden apple).
No species on planet earth has ever before barfed up a forbidden apple. The general principle in the biological world is "see food, eat food". It applies to every life form from bacteria on up.
Our species has managed to turn coal into sugar. It's a clever bit of business in the department of thermodynamic laundering, but hardly the cleverest trick mother nature has yet tossed into the soup—were it not for the human fixation on human exceptionalism.
Prudence might actually be the right path forward. I was in favour of prudence growing up in the 1970s, a point in time where it would have been almost trivial to enact. What was then coming out of most tail pipes was richer in unburnt hydrocarbons than much of what now comes out of the ground. It was one of the hardest things to understand about the world back when I was that age. I now understand that what America was paying for hydrocarbons from the Middle East was a tiny fraction of the wealth one could create through its consumption, this being the primary reason the race was on—the race to exhaust what was already then strongly suspected of being a soon-limited resource. Had the western world slowed its consumption out of prudence, less of the wealth would have crossed the divide. That was too high a price on prudence in the Nixon era, and realistically, it probably still is, because—you know—Sun Tsu and Machiavelli have grown so outdated since the advent of the microchip they are now relegated to the category of mere historical curiosities along with books, and land lines, and VHS.
One of the first professional software developers I ever met was a young fellow driving a first or second generation Honda Civic as The Right Thing To Do (circa 1979). Since then, because the debate has been hijacked by self-serving neo-Luddites vs anyone with even half a clue, the science itself gets more smug by the day. So far as I'm concerned, there is no scientific certainty or consensus on the appropriate societal response to these changes which appear to be taking place with ever greater confidence, though not yet as judged by the standards of scientific process established over hundreds of years as taking hundreds of years, in the ideal case.
Increasingly they just wave around the smoking gun—the gun, the gun, the gun, we've proven the smoking gun—and then they expect their policy recommendations to be given the same heft as the conclusions they are actually trained to reach. Are they crisis management experts? Are they economists? Are they political scientists? Have they traced the precautionary principle all the way back to the primordial soup?
There's no great track record of science getting anything much right over time periods of under twenty years. Give me a century any day. Every year I read another paper outlining yet another carbon sink now suspected. The target is still bobbing around faster than a UFO hand-filmed from a topless Corvette before the invention of wishbone suspension. It's absolutely clear that there's an anthropic contribution to the future condition of the blue marble. I wouldn't have argued against that in the mid-seventies barely out of elementary school. We simply can not un-eat the apple of our own success. Any precautionary principle that suggests otherwise is no precaution of mine. (Side note: The Catholic church did us no favours in this department, not since way back, by making human procreation the prerequisite for animal-nature equilibrium.)
I bear the same hostility toward the anthropic principle physicists, who want us to believe that this new physics dovetails with the past eminence of physics as we have grown to know it. Not at all. This anthropic business is an entirely new and highly dubious venture, and by no means warranting a free pass just because the proponents of this new approach trained beside physicists who still actually do experiments.
This IPCC science—whatever it turns out to be—is not the science of my childhood that I have grown to know and love. It's a whole new beast, with a whole new urgency, an urgency unbecoming of the sober enterprise they claim to represent. And that's a scary things, boys and girls, when they claim to hold the balance of the planet in their palms. I hope they realize somewhere deep down just how far out on a limb this newly discovered enlightenment really is.
We all know where this ends—should the human species even survive: being told that had they not advocated 2C in 2014, we would never have held the line on 3C in 2080. Even if they're wrong, they'll still be vindicated. Where have we seen this shit before?
Neo-con: There's no solid evidence the stimulus package accomplished anything useful at all.
Paleo-lib: Without the hopelessly inadequate stimulus we actually enacted, we'd be infinitely more SOL than we have now become.
First law of hard nature: If you've got a good rejoinder to any outcome at all, there's barely a hint of real science in whatever it is you think you're doing. Even the outcome we actually get can't be construed as non-stochastic, so the chance that this ever turns into hard science of the first order is not high.