In a clear sign of continuing long-term climate change associated with record atmospheric concentrations of greenhouse gases, 2015, 2016, 2017 and 2018 have been confirmed as the four warmest years on record.
A consolidated analysis by the World Meteorological Organization of five leading international datasets showed that the global average surface temperature in 2018 was approximately 1.0° Celsius (with a margin of error of ±0.13°C) above the pre-industrial baseline (1850-1900). It ranks as the fourth warmest year on record.
The year 2016, which was influenced by a strong El-Niño event, remains the warmest year on record (1.2°C above preindustrial baseline). Global average temperatures in 2017 and 2015 were both 1.1°C above pre-industrial levels. The latter two years are virtually indistinguishable because the difference is less than one hundredth of a degree, which is less than the statistical margin of error.
“The long-term temperature trend is far more important than the ranking of individual years, and that trend is an upward one, “ said WMO Secretary-General Petteri Taalas. “The 20 warmest years on record have been in the past 22 years. The degree of warming during the past four years has been exceptional, both on land and in the ocean.”
“Temperatures are only part of the story. Extreme and high impact weather affected many countries and millions of people, with devastating repercussions for economies and ecosystems in 2018,” he said.
“Many of the extreme weather events are consistent with what we expect from a changing climate. This is a reality we need to face up to. Greenhouse gas emission reduction and climate adaptation measures should be a top global priority,” said Mr Taalas.
The globally averaged temperature in 2018 was about 0.38°C (±0.13°C) above the 1981-2010 long-term average (estimated at 14.3°C). This 30-year baseline is used by National Meteorological and Hydrological Services to assess the long-term averages and inter-annual variability of key climate parameters, such as temperature, precipitation and wind, which are important for climate sensitive sectors such as water management, energy, agriculture and health.
WMO will issue its full Statement on the State of the Climate in 2018 in March. This report will provide a comprehensive overview of temperature variability and trends, high-impact events, and key indicators of long-term climate change such as increasing carbon dioxide concentrations, Arctic and Antarctic sea ice, sea level rise and ocean acidification.
The final statement will include information submitted by a wide range of United Nations agencies on human, socio-economic and environmental impacts as part of an effort to provide a more comprehensive, United Nations-wide policy brief for decision makers on the interplay between weather, climate and water and United Nations global development goals.
Australia had its warmest January on record, with heatwaves unprecedented in their scale and duration. Tasmania had its driest January on record, with destructive bushfires. There has been a long-term increase in extreme fire weather, and in the length of the fire season, across large parts of Australia, according to its Bureau of Meteorology.
Intense heatwaves are becoming more frequent as a result of climate change.
Extreme heat in the southern hemisphere contrasted with extreme cold in parts of North America in January.
“The cold weather in the eastern United States certainly does not disprove climate change,” said Mr Taalas. “The Arctic is warming at twice the global average. A large fraction of the ice in the region has melted. Those changes are affecting weather patterns outside the Arctic in the Northern Hemisphere. A part of the cold anomalies at lower latitudes could be linked to the dramatic changes in the Arctic. What happens at the poles does not stay at the poles but influences weather and climate conditions in lower latitudes where hundreds of millions of people live,” he said.