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Yes, really, 350 ppm
Alex Steffen, 26 Mar 08

Ally Andy Revkin has a good post up on Jim Hansen's latest paper, in which Hansen and his co-authors reaffirm their belief that humanity needs to aim to stabilize global CO2 levels at 350 ppm.

Here's the critical excerpt:

We suggest an initial objective of reducing atmospheric CO2 to 350 ppm, with the target to be adjusted as scientific understanding and empirical evidence of climate effects accumulate. Limited opportunities for reduction of non-CO2 human-caused forcings are important to pursue but do not alter the initial 350 ppm CO2 target. This target must be pursued on a timescale of decades, as paleoclimate and ongoing changes, and the ocean response time, suggest that it would be foolhardy to allow CO2 to stay in the dangerous zone for centuries. A practical global strategy almost surely requires a rising global price on CO2 emissions and phase-out of coal use except for cases where the CO2 is captured and sequestered. The carbon price should eliminate use of unconventional fossil fuels, unless, as is unlikely, the CO2 can be captured.

A reward system for improved agricultural and forestry practices that sequester carbon could remove the current CO2 overshoot. With simultaneous policies to reduce non-CO2 greenhouse gases, it appears still feasible to avert catastrophic climate change. Present policies, with continued construction of coal-fired power plants without CO2 capture, suggest that decision-makers do not appreciate the gravity of the situation. We must begin to move now toward the era beyond fossil fuels. Continued growth of greenhouse gas emissions, for just another decade, practically eliminates the possibility of near-term return of atmospheric composition beneath the tipping level for catastrophic effects.

The most difficult task, phase-out over the next 20-25 years of coal use that does not capture CO2, is herculean, yet feasible when compared with the efforts that went into World War II. The stakes, for all life on the planet, surpass those of any previous crisis. The greatest danger is continued ignorance and denial, which could make tragic consequences unavoidable.

It's worth restating here that few people think that even in the best case scenario we're going to be able to avoid driving atmospheric levels up more before we bring them back down -- the difference between stabilization and peak targets.

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feasible when compared with the efforts that went into World War II

I've heard (and agreed with) this a lot. The crucial difference, though, is that populations in WWII were reacting to the imminent, palpable threat of other countries with bombs ready to go. As we know, when the threats posed by climate change are imminent and palpable to the populations who need to totally transform their lifestyles, it'll be too late. I'm all for optimism, and there's a first time for everything, but let's be clear that there is no real historical precedent for the task at hand.

Posted by: Gyrus on 27 Mar 08

There's a good post on Switchboard today about Hansen's recent papers -- NRDC's climate-science guy Dan Lashof makes the point that if Hansen, long the preeminent mind in the field, says that we must -- and can -- cut atmospheric coal down to 350 ppm, we really, really ought to listen: "Hansen has compiled a remarkable track record of publishing testable hypotheses that have been born out by subsequent data.... Twenty years ago [he] went out on a limb to warn us that pollution-driven global warming was underway. We mostly ignored him to our everlasting regret. He is out on a limb again. If we ignore him this time we may find that we are all on the limb with him and that it is being sawn off."

Posted by: Ian Wilker on 27 Mar 08

I saw Bill McKibben make the same plea at SXSW a couple of weeks ago. In fact, he's started a web-based movement called, in fact.

Posted by: Toby on 28 Mar 08

It's interesting that he specifically mentions changes to agricultural and forestry practices. I've been wondering recently if we might actually be able to get a pretty major carbon sequestration effort going just by applying the Rodale Institute's findings on the carbon sequestering potential of intensive organic farming, and using that to justify a major change in farm policy. You'd have to fight agribusiness on it, but in terms of concentration of power and wealth, agribusiness is much lower on the totem pole than other major players.

And honestly as cap and trades take off and an industry develops for carbon sink bundling (as is already starting to happen with forestry) then maybe this could happen alongside government policy reform. If a slew of organic farms could get bundled together for a major carbon credit, it might create a pretty strong mechanism for rapid change.

Posted by: donald on 30 Mar 08

Hey thanks for the great blog, I love this stuff. I don’t usually do much for Earth Day but with everyone going green these days, I thought I’d try to do my part.

I am trying to find easy, simple things I can do to help stop global warming (I don’t plan on buying a hybrid). Has anyone seen that is promoting their Earth Day (month) challenge, with the goal to get 1 million people to take their carbon footprint test in April? I took the test, it was easy and only took me about 2 minutes and I am planning on lowering my score with some of their tips.

I am looking for more easy fun stuff to do. If you know of any other sites worth my time let me know.

Posted by: Adrian on 31 Mar 08



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