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Posted at 11:00 AM ET, 05/11/2009

Scientists Suggest Re-framing Emissions Goals

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"Climate scientists have begun to feel like a bunch of Noahs - thousands of Noahs," University of Victoria in British Columbia climate scientist Andrew Weaver told the British science journal Nature, in an article in its April 30 issue. Weaver was alluding to a building sense of frustration, perhaps bordering on desperation, regarding the continuing gulf between research that shows there is an increasingly urgent need to reduce climate disrupting emissions in the next several decades, and the slow pace of climate change policy making to ensure such reductions are achieved.

As several articles and studies in that edition of Nature discuss, perhaps this disconnect can be overcome by re-framing the issue. Up to now, most scientists and policymakers have framed the challenge of mitigating climate change as a matter of trying to limit the concentration of greenhouse gases in the atmosphere to below a particular target, described in terms of parts per million of carbon dioxide equivalent (carbon dioxide is the most important human-produced greenhouse gas ).

Keep reading for more on the challenge of how to frame emissions goals...

The current concentration is about 387 parts per million, and targets that are commonly discussed range from between 350 to 550ppm. Policy solutions, such as so-called "cap and trade" plans, one of which is currently the subject of considerable debate in Congress, or carbon taxes, are being designed with versions of such thresholds in mind.

The targets approach was legally enshrined in a 1992 U.N. Treaty that committed the global community to limiting greenhouse gas concentrations to a level "that would prevent dangerous anthropogenic [man-made] interference with the climate system."

But as the recent edition of Nature spells out, a more effective way to think about the problem, both from a climate science and public policy perspective, may be in terms of how much more greenhouse gas emissions humanity can emit before guaranteeing "dangerous" climate change. In other words, instead of telling policy makers to design solutions that would keep atmospheric greenhouse gas concentrations to a certain, safe level, scientists instead would help define a safe budget of how many future emissions we can afford.

A critical distinction between this approach and concentration targets is that an emissions budget would take into account the considerable scientific uncertainty regarding how the climate system would respond if greenhouse gas concentrations were to climb to, say, 450ppm and level off there for many decades or more.

A computer modeling study published this year in Proceedings of the National Academy of Sciences by NOAA scientist Susan Solomon and colleagues showed that, once greenhouse gas concentrations are stabilized at particular concentration levels, the climate system could require more than a thousand years to bring global average temperatures back down again.

The main reasons it takes so long for the climate system to recover are the inability of natural processes to rapidly cleanse the atmosphere of many long-lived greenhouse gases emitted, and the delayed heat response of the oceans, which warm up slower than the air does.

As Nature writer Richard Monastersky described it, "A focus on total carbon emissions rather than concentrations... wipes away that problem because it demands that concentrations go up and -- eventually -- come back down, never stabilizing at a particular level. So the climate never reaches equilibrium and the uncertain- ties about its long-term response do not matter as much."

Framing climate change mitigation as a greenhouse gas emissions budget problem could be more effective at driving home the point that Weaver and other climate scientists feel they have not succeeded in conveying well enough yet: there is only so much more fossil fuel energy that humanity can use if we hope to avert "dangerous" climate change.

The problem with this re-framing, however, is that the industrialized world, particularly the United States, has not exactly shown a knack for balanced budgets lately. Given current technology, there is no way to implement a 'carbon bailout' if we exceed the emissions budget. And it won't be Wall Street that will judge Washington, but rather Mother Nature, who can be even more unpredictable and vengeful.

As Monastersky wrote, "Unfortunately, the world is behaving as though it expects to be able to arrange a large overdraft. And researchers can only come up with so many ways of presenting the gravity of the carbon problem to the rest of the world."

By  |  11:00 AM ET, 05/11/2009

Categories:  Climate Change, Climate Change, Climate Change

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