To prevent Earth's average temperature from rising more than 2 degrees Celsius above pre-industrial levels, several teams of researchers say that cumulative carbon emissions must be limited to no more than 1 trillion metric tons. The findings, released April 30 in the journal Nature, are daunting because human activity has already exhausted more than half that allotment since the Industrial Revolution began. Human activity will likely emit the rest of that budget in just a few decades, even if emissions are held at the current rate. The two-degree limit comes from the most recent report by the Intergovernmental Panel on Climate Change as a target to reduce the impacts of climate change.

Iran launched a cross-border air attack on Kurdish rebel positions in Iraq May 2—the first time Tehran has used aircraft against Kurdish guerillas. Kurdish border guards claim that Iranian helicopters began shelling three Kurdish villages—Kani Saif, Jomarasi and Kara Sozi—in the remote Panjwin district of Iraq's autonomous Kurdistan region at 1:30 AM local time. The attacks continued for over an hour. The aircraft reportedly did not enter Iraq and there were no reports of casualties.

Police in Germany's capital Berlin arrested nearly 300 at the city's May Day march, with riot police battling hundreds of protesters deep into the night. According to authorities, militants attacked police with rocks, bottles and Molotov cocktails. Riot police responded with tear gas and pepper spray. 237 officers were reported injured. There were also riots reported in Germany's second city Hamburg. (Radio Netherlands, May 2)

Despite the cancellation of the official May Day parade as a measure to combat the spread of "Swine Flu," some 200 workers marched on Ciudad Juárez's central Avenida 16 de Septiembre, chanting "Este día no es de influenza; es de lucha y de protesta" (This isn't a day of flu; it's a day of struggle and protest). At the city's Plaza de Armas, they burned three piñatas representing the educational, economic and labor reforms of Mexico's federal government.

A May Day rally in Tehran, organized by independent Iranian labor organizations, was attacked by security and intelligence forces, with many beaten and arrested. Security forces did not allow some 2,000 people who had come to the city's Laleh Park for the rally to gather, dispersing them with tear gas and baton charges. Violence and arrests are also reported from the city of Sanandaj, where a May Day rally was similarly attacked by police.

Venezuela's President Hugo Chávez April 30 defied the request of his Colombian counterpart Alvaro Uribe to help catch FARC guerrillas that apparently killed eight Colombian soldiers and then fled to Venezuelan territory. Chávez said he had been "very clear with President Uribe and with Colombia: we do not support the Colombian guerrillas...but it is also not our war, it is Colombia's war." He added: "We will not interfere in that war. And there is no point in any kind of pressure. This is what President Uribe knows and what Colombia knows very well."

Seventeen people were arrested on the Dutch Caribbean island of Curaçao for involvement in a drug-trafficking ring with connections to Hezbollah, the police there said April 29. The suspects, detained the previous day, included four people from Lebanon and others from Curaçao, Cuba, Venezuela and Colombia, the police chief, Carlos Casseres, said. Some of the proceeds, funneled through the Middle East, went toward supporting groups linked to Hezbollah in Lebanon, Casseres said. The ring is also accused of forwarding requests from Lebanon for arms to be shipped from South America. (AP, April 30)

A judge for the UN Special Tribunal for Lebanon (STL) has ordered the release of four generals who had been held on suspicion of their involvement in the February 2005 suicide bombing that killed former Lebanese prime minister Rafiq Hariri and 22 others. The court's pre-trial decision came after prosecutor Daniel Bellemare announced Monday that he was declining to seek a continuation of the generals' nearly four-year detention because of a lack of evidence and due to the legal principle of presumed innocence. The generals' release was celebrated with cheers and fireworks throughout Beirut.