The commitment the international community made in Copenhagen in December 2009 to limit climate change to a maximum of two degrees Celsius by the end of the century implies limits to global emissions by 2050, and has brought physical constraints to the decision-making process in this area. These constraints will be very much in the minds of the heads government when they meet this June in Rio at the United Nations Conference on Sustainable Development. Luiz Gylvan Meira Filho, a leading  Brazilian climatologist and former co-chairman of the Science Working Group of the Intergovernmental Panel on Climate Change (IPCC) says emissions limits can be “easily established,” as long as governments agree that nations have differentiated responsibilities. 

On March 28^th, Dr. Meira addressed the issue at a seminar hosted by the Brazil Institute. He spoke on possible criteria to make such differentiation, as a means to facilitate the necessary global engagement in the mitigation of climate change. A former head of the Department of Meteorology at Brazil’s National Institute of Space Research and founder of its Center for Weather Prediction and Climate Studies (CPTEC), the country’s weather and climate modeling facility, Dr. Meira argues that a certain amount of geo-engineering is not a question of choice, but of necessity as a result of emissions that have already occurred.