The five-year stretch from 2011 to 2015 was the hottest half-decade on record, the World Meteorological Organization (WMO) announced Tuesday, pointing the finger directly at human activity. The period was also marked by significant ice melts and rising sea levels, the U.N. agency said in a new report.
The WMO said it evaluated data covering the five years in order to provide greater understanding of warming trends and extreme events over multiple years. That data can assist governments in implementing the United Nations Framework Convention on Climate Change, according to the report.
“The conclusions are very clear that it was the warmest five-year period on record,” WMO Deputy Secretary General Elena Manaenkova said at a press conference on the sidelines of the 22nd session of the Conference of Parties to the UNFCCC in Marrakesh, Morocco.
Among the key findings:
- Based on the mean of three top worldwide datasets, global temperatures from 2011-2015 were were 0.57 degrees Celsius above the 1961-1990 reference period. By comparison, the period from 2006 to 2010 was 0.51 degrees higher than average.
- 2015 was the warmest year in recorded history, with temperatures of 0.76 degrees Celsius above the 1961-1990 reference period.
- Atmospheric concentrations of major long-lived greenhouse gases spiked throughout the 2011-2015 time frame. For example, last year, the annual mean concentration of carbon dioxide in the atmosphere reached 400 parts per million. Roughly 44 percent of all CO2 from human activity from 2004 to 2015 remained in the atmosphere, according to the 2015 Greenhouse Gas Bulletin.
- Melting of ice was widespread outside of the southern ocean. Minimum summer Arctic sea-ice extent at 3.39 million square kilometers was a record low. The 2011 extent was the third loweest on record, followed by the fourth lowest in 2015 under the satellite record after 1979. Meanwhile, “winter maximum extents were below the 1981–2010 mean in all five years from 2011 to 2015,” the report says. In comparison, the Antarctic sea-ice extent for a large portion of the 2011-2015 period exceeded the 1981-2010 mean, WMO said.
- Worldwide sea level began the 2011-2015 period about 10 millimeters below the long-term trend value, connected to a La Niña system at the time. However, sea levels had reached roughly 10 millimeters above the trend by the last half of 2015.
“The effects of climate change have been consistently visible on the global scale since the 1980s: rising global temperature, both over land and in the ocean; sea-level rise; and the widespread melting of ice. It has increased the risks of extreme events such as heatwaves, drought, record rainfall and damaging floods,” WMO Secretary General Petteri Taalas said in a prepared statement.
Example of such major events include the 2010-2012 East African drought connected to roughly 258,000 death, heatwaves that killed over 4,100 lsat year in India and Pakistan, and the 2012 Hurricane Sandy on the U.S. East Coast, which inflicted $67 billion in economic damage, WMO said.
The organization is scheduled to issue early climate findings for 2016 next Monday at COP22, where member nations are focusing on implementation of the Paris Agreement on climate change, which entered into force last Friday.