The solution that I see will be expensive: carbon capture and sequestration from biomass. This is then cardon-negative, and would eventually bring the CO2 down to a tolerable level, if sufficiently widely practiced.

Maybe I’m reading this wrong – but this bit of good news is leading me to conclude that as long as the permafrost release of methane stays low enough, we can offset that natural positive feedback with manmade reductions, right? So with something like over 500 billion tons of carbon in the permafrost – the $64,000 question is what’s the rate of acceleration of the permafrost melt, correct?

With temperature rise locked at another .6 degrees minimum probably more like another 1.0 degree I’d guess, and I’m reading that computer projections are saying 90% of Arctic permafrost will have melted to a depth of 9 feet by 2012, it seems that at minimum acceleration is going to continue, even if the rate is not precisely knowable at the moment. I suspect we’ll be getting allot more data on this over the summer and into the fall this year.

Unfortunately, like much of the climate change data, the choices presented by the uncertainty seem to be between really bad and really, really bad. That kind of uncertainty is not much comforted by the recent flattening of methane emissions I must say.

It may not be a Larson B ice shelf type of moment but it seems to me that we’ve got a runaway train on our hands and I would still characterize the permafrost situation as another tipping point crossed.

It’s fine by me that their are people who think I’m an optimist. I do wonder how those people get through the day. I blog and have a 1 year old daughter.

By the way, if it wasn’t totally clear, I really thought your Salon article was great (with quibble about tipping points) – for what it’s worth….
- Ken

Jim Hansen says that the tipping point for CO2 regarding the “big melt” (my term) is 350ppm. We’re at 383 and climbing I believe. Is Hansen wrong? Otherwise we’ve crossed perhaps the most important tipping point.

The Arctic summer sea ice is disappearing far ahead of schedule. Greenland and the West Antarctic ice sheet melting are accelerating at a breathtaking pace as documented by Eric Rignot. These are surely crossed tipping points, no?

From Daniel Nepstad’s latest papers, it seems that if the Amazon isn’t crossing a tipping point right at this very moment – it’s teetering on a knife’s edge and it may very well happen in the very near term.

The permafrost is melting – in a continually growing area it’s no longer perma now. The bottom line is that the permafrost has crossed a tipping point. You reply that the net methane releases have flattened. I’m not sure how – as clearly the work of such scientists as Katey Walter and Euan Nisbet suggest that the methane releases are accelerating. (please point me to the flattening studies – I’d be appreciative.) Anyway this is a slow feedback, which I would describe as already feeding back. And if the additions are negligible now the cumulative effect of the continued melting will cause terrible results by mid century. Unless we halt the warming, the cat is out of the bag – again, tipping point crossed.

If I may be a little coarse, it’s a bit like saying because the hole in the space shuttle’s wing didn’t cause the shuttle to disintegrate in outer space that no tipping point had been crossed while they were still in space. Yet those astronauts’s fate was already set. Do we really need to be witnessing the disintegration of our climate before we acknowledge what’s happened and is happening?

With 1.5 degree temp rise “built-in” at this point – can we stop at 2 degrees? Above 2 even the conservative predictions get especially horrendous.

The various environmental changes will be non-linear and surprising – but they are coming. I’d suggest that the overall climate state has crossed a tipping point from a state where the changes could be expected to be gradual and “safely predictable” to one where so many variables are falling off the cliff, the only predictably certain thing is that we are falling. I’d suggest that’s a meta tipping point crossed.

Finally, I whole heartedly agree that 80% reductions by 2050 would be astonishing, and the important thing is to get started. I plan to read your book.

Sincerely,
Ken

I am reading your Salon article and you write:
“Even when concentrations stop rising, global temperatures will continue to increase for many decades because it takes a long time for the planet’s temperature to come into equilibrium with any new level of GHG concentrations. Ultimately, by 2100, we will probably need net human GHG emissions to be close to zero, if not negative, to avert catastrophe. We can’t stop global warming in the next decade.”

It is my relatively uninformed opinion that they need to be net zero by 2060. Of course the pace of reductions is important when setting a target date for net zero. A slower initial reduction will push the requisite time of a necessary net zero status closer to the present – or, possibly, simply miss the chance to slow warming sufficiently to avoid catastrophic impacts and positive feedback loops that put the climate in an imposingly radical state that will make current human settlement patterns and agriculture/survival a very different kind of a challenge.

I have a very hard time imagining the next Pres, whoever it may be, taking this position and getting serious enough about the issue to do what it takes — work vigorously, make the necessary deals, but stay focused and on task without compromise.

Hal