This Discussion Paper is a background document to the Forest Sector Outlook Study 2020-2040 (FSOS) for the UNECE region (ECE/TIM/SP/51). It provides the details that are summarized in chapter 4 of the main study. This Discussion Paper provides a comprehensive overview of how forests might be affected in the UNECE region and its five different subregions, how forests might help climate mitigation, and how forest management may need to adapt to changing conditions. Climate change impacts on forests will be profound: extended, warmer growing seasons and higher levels of atmospheric CO2, might enhance productivity, but more frequent and severe events, such as drought or storms could increase the likelihood of fire, outbreaks of pests, and disease. The study applies the Global Forest Products Model to projects the effects of climate change and higher levels of greenhouse gases on forest stocks in the UNECE region and globally, as well as the potential impacts on global roundwood prices, production, and the consumption and trade of wood products. It analyses how carbon stocks may evolve under different assumptions of economic growth, population growth, and climate change and covers the years 2020-2040, starting with 2017 as the base year for projections.