Yesterday at the Hague, delegates from over 160 nations began meeting to try to hammer out details of the 1997 Kyoto agreement which mandated that nations reduce their greenhouse gas emissions to pre-1990 levels by the year 2012. This sixth session of the UN's Framework Convention on Climate Change will have to overcome significant obstacles if delegates are to emerge with an agreement within the conference's scheduled two weeks. To begin with, there is disagreement between the European Union and the United States on the use of "clean development mechanisms" (CDMs), which give states a number of ways of reaching the treaty's targets without actually reducing emissions. Among these is a proposal to allow for the trading of emissions credits -- disparagingly viewed by most environmentalists as licenses to pollute -- and the possibility of states with high emissions investing in reforestation projects in developing countries that would serve as "Carbon sinks" to absorb these emissions. Naturally, the US, responsible for 24 percent of the world's greenhouse gases, favors such measures, while the EU -- believing its recent coastal flood to be greenhouse-related -- opposes them in favor of across-the-board reductions and tough sanctions for noncompliance. The US is also concerned that the current draft allows developing nations, including China and India, to pledge to reach emissions limits in the future, but does not hold them to any legal obligation for failure to do so. The United Kingdom has stated that an effective agreement can be reached with or without US support. However, given that the US is the main producer of greenhouse gases, most analysts feel that an agreement without US cooperation is liable to have little long-term consequence.