Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.
Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years. Furthermore, according to the World Bank’s “Turn Down the Heat” Report, the world is on track to a 4 degree C warmer world, marked by extreme heat-waves and life-threatening sea level rise. Adverse effects of this warming will have a disproportionate impact on the world’s poorest regions and are likely to undermine development efforts and goals.
Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions. Under the Convention, all Parties have agreed to formulate and implement national and regional programs containing measures to mitigate climate change by addressing emissions by sources and removals by sinks of greenhouse gases.