LONDON – After less than a year and a half in which so much energy news seemed troubling – nuclear meltdowns, oil spills, rising gas prices – it might be startling to find out that worldwide installed capacity of renewable energy has now surpassed that of nuclear power. In fact, global investment in clean energy, driven by enlightened, forward-looking national policies, grew to a record $243 billion in 2010, up 30% from the previous year.