Police estimate that between 10,000 and 25,000 demonstrators will gather today in Gothenburg, Sweden, where U.S. President Bush will be called upon by European Union leaders to defend his rejection of the Kyoto treaty on climate change. The 15 E.U. leaders are kicking off a two-day summit, with the environment at the top of the agenda. European Commission President Romano Prodi wants the leaders to back a sustainable development strategy he drafted last month, which include tough targets for cutting greenhouse gas emissions, limiting the growth of transportation infrastructure, and controlling the use of hazardous chemicals.