International

"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.

"Refugee workers in the Sahel region where thousands of Malian refugees are fleeing violence in their country said this week they are witnessing firsthand the knotted challenges of food security, climate change and conflict in Africa."

"TEHRAN, Iran - Computer technicians battling to contain a complex virus last month resorted to the ultimate firewall measures - cutting off Internet links to Iran's Oil Ministry, rigs, and the hub for nearly all the country's crude exports."

Some new lines of evidence are confirming a decades-old conclusion that climate change was the key cause for the end of the ancient Harappan civilization in what is now the Indus valley of India, Pakistan, and neighboring regions.

"Low levels of nuclear radiation from the tsunami-damaged Fukushima power plant have turned up in bluefin tuna off the California coast, suggesting that these fish carried radioactive compounds across the Pacific Ocean faster than wind or water can."

"The latest round of international climate change talks finished on Friday in discord and disappoint

"TOKYO — What passes for normal at the Fukushima Daiichi plant today would have caused shudders among even the most sanguine of experts before an earthquake and tsunami set off the world's second most serious nuclear crisis after Chernobyl."

"Hopes are fading that climate talks in Qatar late this year will make even modest progress towards getting a new globally binding climate deal signed by 2015, as preliminary negotiations in Germany this week have left much work to be done."

The Atlantic Hurricane season starts officially June 1. Hurricane Bud, a Pacific storm, weakened to Category 2 as it approached Mexico, and NOAA is watching another potential storm off the East coast of Florida. Tropical storm Alberto, which formed Saturday off South Carolina, dissipated Tuesday over the Atlantic without ever reaching shore. Meanwhile, NOAA issued its official forecast, which echoed earlier private forecasts for a fairly normal 2012 season, despite the early start.

"BEIJING --  China’s Commerce Ministry accused the United States government on Thursday of violating free-trade rules through support for six renewable energy projects, but did not identify the projects or the trade rules that had allegedly been violated. It was the latest volley in a widening conflict between the two countries over clean power.

The United States and China, the world’s two biggest energy users, have pledged to work together to develop renewable sources. But they accuse each other of improperly subsidizing or protecting their manufacturers.