World leaders have been adding their voices to those of scientists on climate change, following the latest warning that levels of greenhouse gases in the atmosphere reached a record high last year.<br /><br /> The World Meteorological Organization (WMO) has produced evidence showing that carbon dioxide levels have climbed steadily each year since reliable records began in 1984.<br /><br /> “We have broken a new record once again. Over the last 25 years between 1990 and 2014, there was a 36 percent increase in the radiative forcing of greenhouse gases,” said the World Meteorological Organisation’s Secretary-General Michel Jarraud.<br /><br /> UN weather/climate agency chief calls for urgent action on #greenhousegas https://t.co/kD7eRTeObp #COP21 WMOnews pic.twitter.com/h8bUBWRtyd— UN Geneva (UNGeneva) November 9, 2015<br /> <br /><br /> Officials including environment ministers from dozens of countries have started early negotiations ahead of the UN Climate Change Conference COP21 which starts at the end of the month in Pa
