The head of the United Nations Environment Programme (UNEP) has pushed for moves to cut emissions of a range of greenhouse gases and pollutants along with carbon dioxide to more effectively combat climate change, improve human health and reduce damage to crops. Scientists estimate that non-carbon dioxide pollutants, such as black carbon, methane, low-lying ozone and nitrogen compounds, make up some 50 per cent of emissions causing global warming, according to UNEP. Achim Steiner, UNEP Executive Director, underscored the urgency for additional scientific assessments of such pollutants, as well as options for action: "There remains some scientific uncertainty about some of these pollutants' precise contribution to global warming, but a growing body of science points to a potentially significant role." Stressing that the world must deploy all available means to fight global warming, he said that no substance contributing to climate change or any measure to mitigate it should be overlooked. "The international community's over-arching concern must be to seal a convincing deal at the UN climate change meeting in Copenhagen in less than 100 days time � one that puts the world on track towards swift and significant cuts in carbon dioxide while also providing the funding to assist vulnerable countries and communities to adapt," said Mr. Steiner. Black carbon � soot mostly from diesel engines, coal-fired stations and burning wood and dung � is key among a range of air contaminants that are also linked to over 1.6 million premature deaths a year resulting from indoor exposure and 800,000 from outdoor exposure, said UNEP. UNEP spotlighted tropospheric ozone � including near-surface ozone which is often called smog � as a major greenhouse gas linked to harming human health and causing significant damage to crops and ecosystems.