Meteorologists: Spring Hottest on Record for Northern HemisphereThe World Meteorological Organization says the Northern Hemisphere has experienced the hottest spring on record as global temperatures reached a new high in May. David Carlson, director of the WMO's World Climate Research Program, said this week that the climate system is changing and that what used to be abnormal is becoming the new normal. He said global levels of carbon dioxide — the main greenhouse gas that leads to global warming — have never been higher. “May has been warmer," he said. "It is warmer ... by almost 1 degree Celsius ... and this is the eighth month that we are at or above 1-degree C warming. So, something is telling us that the system is changing.” WMO scientists said the heat has been especially pronounced in the Arctic, resulting in an extreme amount of Arctic sea ice and Greenland ice sheet melting early this year. Carlson said what happens in the Arctic affects the rest of the globe. “Northern Hemisphere snow cover has never been lower in the 50-year record," he said. Barrow, Alaska, recorded its earliest total loss of snow to melting on record, and the statistics go back 78 years, he said. Carlson said there now have been 370 consecutive months of warm or warmer-than-average surface temperatures. He noted the record temperatures in May have triggered other extreme events. These include heavy precipitation in parts of Europe and the southern United States, as well as widespread and severe coral reef bleaching in Australia’s Great Barrier Reef and other parts of the world.