BergZ writes: The world's air has reached what scientists call a troubling new milestone for carbon dioxide, the main global warming pollutant. Monitoring stations across the Arctic this spring are measuring more than 400 parts per million of the heat-trapping gas in the atmosphere. The number isn't quite a surprise, because it's been rising at an accelerating pace. Years ago, it passed the 350 ppm mark that many scientists say is the highest safe level for carbon dioxide. It now stands globally at 395.
BergZ writes: Scientists from around the world are providing even more evidence of global warming. "A comprehensive review of key climate indicators confirms the world is warming and the past decade was the warmest on record," the annual State of the Climate report declares. Compiled by more than 300 scientists from 48 countries, including Canada, the report from the National Oceanic and Atmospheric Administration said its analysis of 10 indicators that are "clearly and directly related to surface temperatures, all tell the same story: Global warming is undeniable."
BergZ writes: The Ordovician ice age happened 444 million years ago, and records have suggested that CO2 levels were relatively high then. But when Seth Young of Indiana University in Bloomington did a detailed analysis of carbon-13 levels in rocks formed at the time, the picture that emerged was very different. Young found CO2 concentrations were in fact relatively low when the ice age began.