Envoys from more than 180 nations on Monday held crucial talks in Montreal on the UN Kyoto Protocol on curbing greenhouse gases, amid warnings from scientists and environmentalists that climate change could have profound consequences. Experts pointed out that developing countries like China and India will now have to contribute to anti-pollution controls. Further, the present commitment period does not include the planet's worst polluter, the United States, which walked away from the protocol in 2001 because of the high cost of meeting its Kyoto targets.