Countries representing 190 nations are participating in United Nation Framework Convention on Climate Change talks in Bonn this week and next. At stake is nothing less than the fate of the world.

The meetings in Bonn kick off a process that (hopefully) will culminate in Copenhagen in December with a new pact for curbing greenhouse gases beyond 2012, when provisions under the Kyoto Protocol expire. At long last, after eight years of dithering by the Bush administration, the U.S. is promising to be “powerfully, fervently engaged” in the global talks.

Andrew Jones and Elizabeth Swain at Climate Interactive have collected emissions reductions proposals from countries or groups of countries that have made publicly available proposals for reductions of greenhouse gas emissions (“current proposals” in the graph below) and have modeled the outcomes. They found:

Even if they were fully implemented they would be far from sufficient to meet the goal of stabilizing atmospheric CO2 levels at or below 450 ppm, reaching instead about 730 ppm by 2100.

If the UNFCCC process is to achieve widely accepted climate goals – such as stabilizing CO2 levels between 350-450 ppm and limiting temperature increase to less than 2°C over pre-industrial – then, in the next nine months, the talks will need to result in a global agreement at least as ambitious as the European proposal. But agreements are one thing, actual results another. The EU’s climate plan isn’t delivering the reductions that have been promised.

Only the “80% scenario” – an 80% reduction of global fossil fuel emissions by 2050, relative to 1990 levels, plus a 90% reduction in land use emissions by 2050, relative to 2009 levels – succeeds in limiting CO2 levels to approximately 400 ppm CO2 at 2100.

The bad news is limiting atmospheric CO2 levels to 400 ppm may not be enough to avoid climate catastrophe. The model used lacks many of the positive feedback loops that more and more are being found to exist in the climate system (e.g., feedbacks between temperature and carbon in soil and biomass, and feedback between temperature increase and other greenhouse gasses such as methane in hydrates and permafrost). The absence of such feedback processes in the model implies that temperature increases in the ‘real’ system could be larger than in the simulation runs.

The United States and China are the world’s largest polluters, combining for nearly half of all global emissions. Per capita, the United States emits about four times as much as China.

Obama has promised to cut US emissions about 15% (from 2007 levels) by 2020 and 80% (again, from 2007 levels) by 2050. That’s far short of what the EU is proposing: 20% compared to 1990 levels by 2020 and by 30% if other industrialized countries follow suit, and 80% from 1990 levels by 2050.