The five-year period from 2011 to 2015 has been the warmest five-year period on record globally, with 2015 being the warmest year on record to date.1 The period 2011–2015 was also the warmest on record for every continent except Africa. During this period, concentrations of the major greenhouse gases continued to rise and reached record levels for the instrumental period.
This report describes the evolution of the climate system during the period 2011–2015. The World Meteorological Organization (WMO) has assessed this five-year period in order to contribute to a better understanding of multiyear warming trends and extreme events that can help governments to implement the United Nations Framework Convention on Climate Change more effectively. This applies in particular to the 2015 Paris Agreement, which provides a historic opportunity for the global community to act with greater urgency in curbing greenhouse gas emissions, fostering climate resilience and mainstreaming climate adaptation into national development policies.
The record high temperatures from 2011 to 2015, along with the annual record set in 2015, are consistent with established long-term warming trends, the dominant cause of which is the emission of anthropogenic greenhouse gases. Year-to-year temperature fluctuations occur against the backdrop of the long-term warming trend, in particular as a result of El Niño and La Niña events. High temperatures have been accompanied by the continuation of long-term trends in other indicators that are consistent with warming, such as rising sea levels and declines in Arctic sea-ice extent and in continental glaciers and ice sheets in Arctic and high-mountain regions.