Concentrations of greenhouse gases, the major cause of global warming, are at their highest levels ever recorded and are still climbing, the U.N. World Meteorological Organization said yesterday.

 

The head of the agency, Michel Jarraud, said the trend could be pushing the world towards the most pessimistic assessments of the rise in temperatures expected in coming decades.

 

The worst-case scenario in an IPCC 2007 report was that temperatures could rise between 36 to 44 degrees Fahrenheit by the end of this century.