This 2000 edition of the World Energy Outlook presents probable developments from now to the year 2020. It also represents an important methodological advance. The 1998 and earlier editions were based on a "business-as-usual" approach, which projected energy trends in a world where no new policies were enforced to limit climate change. This year’s WEO offers a new "reference scenario", which takes into account those greenhouse gas policies that have been adopted and are now in place in OECD countries. Alternative cases are also presented. These consider the effects of potential climate-change policies for transport and electricity generation sectors. Another important section studies the potential effects of schemes for trading emission permits among developed countries.