Molecules released by trees can seed clouds, two experiments have revealed. The findings run contrary to an assumption that the pollutant sulphuric acid is required for a certain type of cloud formation — and suggest that climate predictions may have underestimated the role that clouds had in shaping the pre-industrial climate, .i.e. pre-industrial skies were less sunny than thought. If the results of the experiments hold up, predictions of future climate change should take them into account. For 20 or more years, clouds have been the largest source of uncertainty in understanding how manmade emissions affect the atmosphere. http://www.nature.com/news/cloud-seeding-surprise-could-improve-climate-predictions-1.19971
