Boston-area hospitals advanced public health by cutting their energy greenhouse gas emissions by 29 percent between 2011 and 2015, and are on track to reduce 33 percent by 2020, according to a new report released today by Health Care Without Harm. The report includes data from hospitals serving on the Boston Green Ribbon Commission’s Health Care Working Group. Their trajectory delivers a 47 percent reduction in greenhouse gases compared to “business as usual” by 2020.