Record jump in global surface temperatures from 2014 to 2016 has boosted the total amount of warming since 1900 by more than 25 percent in just three years, a study shows.
The study, led by a University of Arizona-led team, has been published online in the journal Geophysical Research Letters.
The researchers analyzed 15 different datasets, including observations of global mean surface temperatures from 1850 to 2016, ocean heat content from 1955 to 2016, sea level records from 1948 to 2016 and records of the El Niño climate cycle and a longer climate cycle called the Pacific Decadal Oscillation, and found the Earth's average surface temperature climbed about 0.9 Celsius degrees from 1900 to 2013.
By analyzing global temperature records, researchers further found that by the end of 2016, the global surface temperature had climbed an additional 0.24 Celsius degrees, which is unprecedented in the 20th and 21st centuries
Although some release of heat from the Pacific Ocean is normal during an El Niño, the researchers found much of the heat released in 2014-2015 was due to additional warming from increases in the amount of greenhouse gases in the atmosphere.
"The result indicates the fundamental cause of the large record-breaking events of global temperature was greenhouse-gas forcing rather than internal climate variability alone," said lead author Jianjun Yin, a University of Arizona associate professor of geosciences.
The researchers also projected how often a 0.24-Celsius-degree global temperature increase might occur in the 21st century depending on the amount of greenhouse gases emitted worldwide between now and 2100. The team used four representative concentration pathway (RCP) models that project future climate change between 2016 and 2100.
For the low-emission RCP scenario, in which greenhouse gas emissions peak by 2020 and decline thereafter, temperature jumps of at least 0.24 Celsius degrees might occur from zero to two times in the 21st century, the team found.
For the highest-emission RCP scenario, in which greenhouse gas emissions rise unabated throughout the 21st century, spikes of record warm temperatures would occur three to nine times by 2100.
"As a climate scientist, it was just remarkable to think that the atmosphere of the planet could warm that much that fast," said study co-author Jonathan Overpeck, dean of the University of Michigan (UM) School for Environment and Sustainability.
Adapting to the increases in the frequency, magnitude and duration of rapid warming events projected by the higher-emission scenario will be difficult.
"If we can reduce greenhouse gas emissions, we can reduce the number of large, record-breaking events in the 21st century-and also we can reduce the risk," Yin said.