The index, which comprises the top scoring 10% of companies included in the Carbon Disclosure Project's analysis of 200 Nordic companies, scored businesses on their climate change disclosure, focusing on greenhouse gas emissions and reduction targets.
According to UPM, the group has invested more than €1bn (£900m) since the early 1990s in biomass-fired power plants and recovery boilers. Its investments have cut CO2 emissions by 40% per tonne of paper, it claimed.
Anja Silvennoinen, senior vice president of UPM's energy business area, said: "We have a very good track record when it comes to reducing greenhouse gases."
She added: "For example, changes in the fuel mix and improved energy efficiency resulted in a 12% decrease in fossil CO2 emissions per tonne of paper in 2008 compared to 2007."