Guardian: Scientists have raised urgent new concerns over the latest efforts to mitigate the catastrophic oil spill in the Gulf of Mexico caused by the oil rig explosion on BP’s Deepwater Horizon. Latest efforts to limit the environmental damage involve an untried deep-water technique, using a toxic dispersant that they believe may damage ocean life. But the new method has so far only succeeded in ratcheting up the growing controversy surrounding the spill. On Friday, Barack Obama appeared to …