December 14, 2009 by Stephanie McCauley
We’re thrilled that, as one of his final set of blog posts as a staff writer at the NY Times, Andy Revkin chose to cover our Climate Scoreboard and the perspective of Climate Interactive team member Dr. John Sterman of MIT. His post is below and here.
December 13, 2009, 11:54 am
COPENHAGEN — Once in awhile, it’s useful in the midst of conflicting treaty drafts (all those bracketed targets) and confusing national emissions pledges (choose your baseline year) to see how all this verbiage relates to what the atmosphere will experience in decades to come. When framing questions for people with climate claims, in fact, I often find it useful to assume the position of the atmosphere, asking how they would “convince” the sky that their proposals would have a meaningful impact on human-generated emissions.
These days, this has become a bit easier, as several groups have developed fast-response tools that can assess the climatic significance (or lack thereof) of a new emissions pledge. For the Copenhagen talks, three groups, under the mantle of Climate Interactive, have joined forces and produced a single barometer of progress produced by creating an ensemble of their model results.
One partner in this effort is John Sterman at the Massachusetts Institute of Technology, who helped convey the cumulative nature of greenhouse gases with his illustrations of the “bathtub effect” behind the building greenhouse effect.
Above you can see the latest analysis of the shortfall between the combined pledges of countries on carbon dioxide emissions, including a slight shift in Japan’s position reported over the weekend, and one of the thresholds for safety being pushed in the talks here by the poorest developing countries (1.5 degrees Celsius above the global temperature in the 1800s). It’s not a promising picture.
I asked Dr. Sterman to provide a bit more context on the analysis, and the model used to generate these results, which is called C-ROADS. I have to issue a jargon and acronym alert, but I encourage you to read on. The “kicker” is worth the journey:
We use the C-ROADS model to examine the impact of all proposals for emissions reductions that have been made by individual nations that are now on the table at Copenhagen. We classify proposals into “confirmed” or “potential.” Confirmed proposals include official governmentt statements, adopted legislaton, and UNFCCC submissions. Potential proposals include conditional proposals, legislation under consideration and unofficial government statements. Full documentation of our characterization and classification of the proposals is at /scoreboard/scoreboard-science-and-data/current-climate-proposals-1/current-climate-proposals.
The current (as of 12 December) analysis shows that confirmed proposals would cause a rise in expected mean global temperature of 3.9 °C (7.0 °F) above pre-industrial levels by 2100.
The 3.9°C (7.0 °F) warming by 2100 is an improvement of 0.9°C (1.6 °F) over the business as usual increase of 4.8 ° C (8.6 °F), but falls far short of the 2 °C (3.6 °F) target that has been widely adopted and that would reduce the risks of the most serious impacts of climate change. The uncertainty range around the estimate of 3.9 °C from current confirmed proposals means warming could be significantly higher, but there is essentially no chance of limiting warming to the 2 °C target.
This conclusion is reinforced by the joint statement issues on 9 December by all the leading groups that analyze current proposals, including the Grantham Research Institute on Climate Change and the Environment, UNEP, Ecofys, Climate Analytics, the European Climate Foundation and ClimateWorks.
Recent independent analyses of current mitigation proposals on the table in Copenhagen by Nicholas Stern, the United Nations Environment Program (UNEP), the Potsdam Institute for Climate Impact Research (PIK), Ecofys, Climate Analytics, the Sustainability Institute (C-ROADS), the European Climate Foundation and ClimateWorks (Project Catalyst), all point to the same conclusion: the negotiations must deliver the high end of current proposals and stretch beyond them, if the world is to have a reasonable chance of containing warming to below 2°C above pre-industrial levels, or the 1.5°C goal of many developing nations.
Some in the media have written that emissions reductions proposed by 2020 are within a few GtCO2e/year* of the rate required to stay on a path that yields a 50/50 chance of limiting warming to no more than 2 °C. This is misleading. One could quibble about the significance of having current proposals being a few gigatons per year higher than the rate required for the 50/50 chance of 2 °C (a few gigatons here, a few gigatons there; pretty soon you are talking about real warming).
But arguing about whether the 2-degree path requires emissions in 2020 to be 45 or 40 gigatons CO2e/year misses the critical issue. The most important determinant of the level of warming by 2100 is not the rate of emissions in 2020 but the rate in 2050. If emissions do not fall significantly by 2050 (and beyond) then there is no chance of limiting warming to 2 °C. As you can see in this graph, showing results from the C-ROADS model (/blog/2009/12/09/2050-copenhagen-targets-really-matter-15-times-as-much-emissions-abatement-will-happen-post-2020/), the cumulative abatement of emissions needed by 2050 is 15 times larger than the cumulative abatement the low emissions path requires by 2020 (relative to business as usual). If emissions do not continue to fall after 2020 then warming is expected to be well above 2°C. Any agreement coming out of Copenhagen that does not commit the parties to continuing, substantial emissions reductions through 2050 cannot claim to have succeeded in putting the world on a path limiting expected warming to 2 degrees C.
Furthermore, there is a real risk of what we call “eroding goals” — of slipping what we strive for in the face of difficulty. Since when is a 50/50 chance of limiting warming to 2 °C by 2100 acceptable as a target? Sure, that’s better than doing nothing, but who thinks playing Russian roulette with half the chambers loaded is a good gamble? To limit the chance that warming will exceed 2 °C by 2100 to no more than, say, 5%, emissions would have to fall even farther and faster than the “Low Emissions” path in the graph above. That’s still like playing Russian roulette with 1 in 20 chambers loaded. Who among us would play that game? Who among us would play that game when the gun is pointed not at our heads, but at our childrens’?
[*GtCO2e is billions of tons of carbon dioxide or the equivalent amount of other greenhouse gases when measured in terms of their potential to warm things up.]