From May 5 to 7, the Petersberg Climate Dialogue IV was held in Berlin, building upon conversations from the recent Ad Hoc Working Group on the Durban Platform for Enhanced Action. 35 countries and other multilateral organizations participated in the talks which were co-hosted by representatives from Germany and Poland. The discussion focused on the universal climate change agreement the United Nations wants finalized by 2015. At the talks, U.S. lead negotiator Todd Stern said America’s proposal to have countries make and hold public comment periods on greenhouse gas emissions reduction commitments would be beneficial. He said the public comment period would ensure the commitments are something the country is willing to defend. Stern also commented that it is not certain if the announcement that carbon dioxide concentrations in the atmosphere are approaching 400 parts per million (ppm) will impact climate change talks. Environmentalists and scientists commented that the 400 ppm has political, not scientific, significance since the last time concentrations were at 400 ppm was 10 million years ago. Two more international climate talks are expected to be held this year: one in Bonn in early June and the 19th Session of the Conference of the Parties to the U.N. Framework Convention on Climate Change (COP 19) in Poland in November.