Lomborg has presented us with a false premise: that the way to solve the world's problems is simply to throw money at them--after doing a cost-benefit analysis. There is an inherent absurdity that comes along with trying to reduce social and environmental issues to quantifiable--in Dollars or Euros--terms such as "social good" (let's see, how about if we say that the loss of an island nation to sea-level rise has the same value as a 10% change in cancer incidence). It is equally silly to try and draw a dividing line between social and environmental issues, and then depict the two "separate causes" as competitors.
For instance, coal mining intensifies as the demand for energy rises to meet the needs of an expanding population; and burning that coal increases mercury pollution, which increases the incidence of developmental disabilities; of course, coal also contributes to global warming, which harms many communities in the form of drought, more intense hurricanes, and loss of coastline. Not to mention that working in a coal mine is extremely dangerous--in 2006 a BBC story reported that as many as 6,000 coal miners die every year in mine accidents in China alone.
Socio-environmental problems can not be fixed by separating out their various components. In fact, separating "environmental" and "social" issues from one another virtually guarantees that more egregious eco-social problems will arise.