Close to 4,000 people from 163 countries converged on Marrakech, Morocco, today for the beginning of a two-week conference on the Kyoto treaty on climate change. The opening was characterized by unusually heavy security, because the conference is the largest international gathering to be held since Sept. 11 and the first in a Muslim country. Delegates hope to forge a legally binding agreement to slow climate change, and will seek ratification of that agreement by 55 nations, including countries that together produce more than 55 percent of the industrial world’s greenhouse gas emissions. Although the Bush administration has pulled out of Kyoto, it sent representatives to Marrakech to ensure that the terms of the final accord do not create indirect costs for the U.S. or set unwanted precedents.