The amount of global warming-causing greenhouse gases in the atmosphere rose to a new high in 2010, and the rate of increase has accelerated, the UN weather agency said on Monday. Levels of carbon dioxide -- a greenhouse gas and major contributor to climate change -- rose by 2.3 parts per million between 2009 and 2010, higher than the average for the past decade of 2.0 parts per million, a new report by the World Meterological Organisation found.