We're running out of time

The atmosphere is lethal

But I will fear no evil

Because it's not too late,

It's not too late.
-- T-Bone Burnett

Marvelous musician and cracker-jack producer that he is, (responsible for last year's stellar Alison Krauss-Robert Plant collaboration), T-Bone may be dead wrong when it comes to doing something about the climate crisis. So conclude a quartet of researchers from Princeton University and the Brookings Institution. The problem is, we may have waited too long to start bringing down greenhouse-gas emissions.

"Atmospheric stabilization and the timing of carbon mitigation" appears in the current Journal of Climatic Change (DOI: 10.1007/s10584-007-9391-8). Bryan Mignone, Robert Socolow (co-author of the wedge strategy for emissions reduction) et al take on the common attitude among economists, including those associated with the IPCC, that we should delay deploying new climate-change-mitigation technologies for a while, because they'll be cheaper in the future, more cost-effective ;;;;; and faster ;;;;; the longer we wait. Bjorn Lomborg likes to make a similar argument, for similar reasons. Mignone and his co-authors sum up that silly argument like this:

With some notable exceptions (e.g. Yohe et al. 2004; Webster 2002; Ha-Duong et al. 1997), most economic analyses of climate change have concluded that, whenever tradeoffs can be made, some postponement is preferable to immediate action (e.g. Wigley et al. 1996).

The flaw is obvious: natural constraints can easily trump economic strategies. For example:

"... even before the physical constraint binds, it seems likely that the high costs associated with a future rapid decline in emissions would make modest advancements in the onset of mitigation preferable, even when costs are evaluated in terms of net present value.

There are, of course, precious few known predictive data points when it comes to calculating the effects of future fossil-fuel emissions, making the task of estimating how fast we have to reduce them in order to avoid catastrophic climate change rather difficult. But Mignone et al work with what he have, which is the conventional understanding that a doubling of CO2 emissions over the pre-industrial level of 275 parts per million is something we want to avoid. So the question becomes, how aggressive do our mitigation strategies have to be to keep the peak, or "frontier," below 550 ppm? Their answer is:

Assuming a decline rate of 1% year^-1 and a neutral terrestrial biosphere in which net terrestrial emissions are assumed to be zero), we find that immediate mitigation would place the frontier near 475 ppm and that each additional year of delay increases it by about 9 ppm on average, meaning that stabilization below a pre-industrial doubling will require the onset of dedicated mitigation within about a decade.

So if their calculations are correct we have 10 years to start chopping emissions by a mere 1 percent each year. Any further delay, and we're doomed. They add that "as mitigation is postponed, the rate at which societal options disappear actually increases."

For "societal options," read the political tradeoffs between rich and poor countries, the advantages of cap and trade vs. carbon taxes, and so forth. In theory, the authors are saying, we have the luxury of arguing about such things now. But it won't be long before mandatory, and draconian measures will be come the only tools left. Thanks to the inertia involved in the climate forcings, the changing ability of oceans to absorb some that CO2 and other factors, "some amount of postponement cannot be fully offset by simply increasing the intensity of future mitigation."

All of the various scenarios generated by Mignone's team ares predicated on the goal of keeping CO2 levels somewhere between 450 and 550 ppm, which is fair. You've got to pick some number. But there are great many observers out there who would say those kind of numbers constitute a recipe for disaster and we've got to aim for something much lower. This is not to say that Mignone, Socolow and their colleagues aren't keeping up with the program. But their paper was written in September of 2006. It just took far too long to work its way through the publishing process, appearing only a month ago.

Their choice of numbers was made before last winter's unprecedented melt of the north polar ice. Before the lastest figures on the speed at which Greenland's glaciers are disappearing and a whole of other worrisome trends that didn't make it into the IPCC's Fourth Assessment either. Now you hear respectable folks talking about 350 ppm as the safe level, even though we've already blown past that mark.

Responding to such scientific advice, author Bill McKibben, perhaps second only to Al Gore in the pantheon of climate crisis activism, has just launched a new movement organized around a goal of getting us back to 350.

This past week, Lester Brown of the Earth Policy Institute writes in his new book, Plan B 3.0, , that what we really need is "a detailed plan to cut carbon dioxide emissions 80 percent by 2020." Compare and contrast that with the Mignone scenario of cutting emissions by a single percentage point each year. To get rid of 80 percent in 12 years will require between 3 and 4 percent a year. This is an era when demand for electricity and transportation fuels is almost certainly going to increase by at least that much.

Of course, all of this would be moot if we could just invent some kind of newfangled gadget that sucks carbon dioxide from the air. Even better would be technology that then takes that CO2 and turns it into a fuel we can burn. Duncan Graham-Rowe writes about the latest advances on that front in last week's New Scientist. Lots of optimism in the lab, but so far every method we've come up with gobbles oodles of energy. Which is what gave us this problem in the first place.

Mignone, B.K., Socolow, R.H., Sarmiento, J.L., Oppenheimer, M. (2008). Atmospheric stabilization and the timing of carbon mitigation. Climatic Change DOI: 10.1007/s10584-007-9391-8