San Francisco Chronicle: If Hashem Akbari’s plan to stave off global warming is realized, it will come one rooftop at a time. Akbari, a senior scientist at the Lawrence Berkeley National Laboratory, and a group of fellow geoengineers who are trying to counter the effects of climate change, have developed a relatively simple idea to offset carbon emissions and cool the Earth’s urban surfaces: Make all rooftops and paved surfaces white. Or at the very least, convert them to cool gray colors to reflect …