Reining in greenhouse gas emissions has been an international priority for decades. Under the United Nations Framework Convention on Climate Change (UNFCCC) adopted in 1992, the Kyoto Protocol (1997) set legally binding targets for cutting emissions in economically developed countries, and the Copenhagen Accord (2009) highlighted the importance of keeping average global temperature increases below 2 °C. After more than two decades of negotiations, the member states of the UNFCCC are meeting in Paris for the 21st Conference of the Parties (COP21) to forge a new agreement and to set mitigation targets post-2020. Here, we look back on some successes and missed opportunities for climate mitigation since 1990, the benchmark year for the Kyoto Protocol. We also present new data for 2014 and a projection for 2015 indicating that the rapid growth in global CO2 emissions from fossil fuels and industry since 2000 slowed dramatically in the past two years (Fig. 1), despite continued global economic growth. Time will tell whether this surprising interruption in emissions growth is transitory or a first step towards emissions stabilization. In either case, the trend is a welcome change from the historical coupling of CO2 emissions with economic growth and should be strengthened through efforts at the Paris COP and beyond.