Actual Carbon Emissions vs. IPCC Scenarios - how far away is safety?

[GliderGuider]

2. This is the curve that Bill McKibben's "Do the Math" tour is all about.

http://math.350.org/

According to McKibben's numbers, we have enough fossil fuel (2795 GtC) to last until about 2090 on my projection.
And, if we accept McKibben's number of 565 GtC as the maximum safe amount we can emit, we'll hit that around 2040.

There are only two things that I can see that might interfere with that course of events. One is the declining EROEI of fossil fuels (especially oil), and the other is the collapse of the globalized industrial economy (and a little bit later, civilization itself) due to a combination of rising fossil fuel EROEI and rising planetary temperature.

We are unlikely to see renewables magically slow that curve, no matter how well (or not) Germany is doing at that. It would take too long for the replacement to kick in, the number of nations involved is too large, and their self-interest is too strong - as long as the fossil fuels are affordable and offer an EROEI over about 5:1 we will burn them. According to a recent draft paper I've seen by Charles Hall, 5:1 is well below the level necessary to maintain what we think of as a "modern" civilization - he now pegs that at around 14:1.

In any event, we are now committed to +2C of warming, and as Kevin Anderson of Tyndall Cenre warns us, +2 is merely a transition point on the path to +4C. Which means we will see +4, probably by mid-century. Given that what we're now seeing at +0.8C is what we recently expected to see at +2, the world at +4 is likely to resemble the world we hadn't planned on until +5 or +6. Here is what RealClimate says about that, in a review of Mark Lynas' book "Six Degrees: Our Future on a Hotter Planet":

http://www.realclimate.org/index.php/archives/2007/11/six-degrees/

At 5° and 6°, the book really does start to sound alarmist, with the analogy to Dante’s Inferno – used to good literary effect throughout the book – coming very much to the fore. At five degrees, we have “an entirely new planet is coming into being – one largely unrecognizable from the Earth we know today. At six degrees, “… the pump is primed … not for flourishing palm trees in Alaska, but for the worst of all earthly outcomes: mass extinction.”

Aha, say the skeptics! It is alarmist after all. But is it? Lynas’s reference to the “entirely different planet” actually refers to the fact that at five degrees, the “remaining ice sheets are eventually eliminated from both poles.” That’s entirely true. And unlike in Gore’s discussion of sea level in Inconvenient Truth Lynas does emphasize the long timescales (thousands of years) in this case. Furthermore, there is published research that raises the likelihood of the significant loss of ice sheets at lower temperatures, and Lynas could have claimed certainty of a disappearing Greenland ice sheet in an earlier chapter. That he doesn’t do that is characteristic of the book: it doesn’t tend to go beyond the published literature. This is what Lynas claims at the outset — “all of the material in the book comes from the peer-reviewed scientific literature” – and I think he does an admirable job.

And that brings us back to the question I promised to raise at the beginning, which is this:

If a reading of the published scientific literature paints such a frightening picture of the future as Six Degrees suggests – even while it honestly represents that literature – then are we being too provocative in the way we write our scientific papers? Or are we being too cautious in the way we talk about the implications of the results?

Extinction. It's not just McPherson and me saying stuff like this.