This paper summarizes the main results of a study on the costs of abatement of CO2 emissions in Brazil. It discusses three possible futures for the long run (2010 and 2025) activity of the Brazilian economy and -- with the help of a linear programming model for Brazil's energy sector -- three scenarios for energy production and use. One of these scenarios illustrates the possibility of halving future carbon emissions originating from energy generation and consumption, with relatively small increases in energy associated costs and investments. This abatement scenario would require, on the supply side of the Brazilian energy balance, increased amounts of hydropower, ethanol and bagasse from sugarcane, plus wood and charcoal from reforestation [...]