This report explores the environmental and economic effects of the pledges submitted by industrialized and major developing countries for 2020 under the Copenhagen Accord and provides an in-depth comparison with results arrived at in other model analyses. Two scenarios reflect the lower (“weak”) and upper (“ambitious”) bounds of the Copenhagen pledges. In addition, two scenarios in accordance with the IPCC range for reaching a 2°C target are analyzed with industrialized countries in aggregate reducing their CO2 emissions by 30 % in 2020 compared to 1990 levels. For all four policy scenarios the effects of emission paths leading to a global reduction target of 50 % below 1990 levels in 2050 are also simulated for 2030. In addition, a separate scenario is carried out which estimates the costs of an unconditioned EU 30 % emission reduction target, i.e. where the EU adopts a 30 % emission reduction target in 2020 (rather than a 20 % reduction target), while all other countries stick with their “weak” pledges. Not included in the calculations is possible financial support for developing countries from industrialized countries as currently discussed in the climate change negotiations and laid out in the Copenhagen Accord.