Even with La Niña, 2021 ranks as one of hottest years on record

Despite global temperatures being tempered by the onset of consecutive La Niña events, 2021 has ranked among the seven hottest years on record, according to an assessment published by the World Meteorological Organisation.

According to the latest global temperature update published by the international body, average global temperatures for 2021 were estimated to have reached 1.11°C above pre-industrial levels, seeing 2021 become the seventh consecutive year where global temperatures have exceeded 1°C above pre-industrial levels.

The result also means each of the seven warmest years on record has occurred since 2015 – with 2016, 2019 and 2020 continuing to rank as the top three hottest.

The WMO said the latest figures further underscored the evidence of the continuing impacts of global warming on temperatures and noted that the temperature anomaly was higher than those observed during earlier La Niña events.

La Niña events, which see cooler ocean surface temperatures across much of the Pacific Ocean, generally lead to a temporary reduction in global average temperatures and bring higher levels of rainfall to Australia’s eastern regions. However, the effects offer a temporary reprieve from rising temperatures, including the extremes often observed during the warmer El Niño events.

“Back-to-back La Niña events mean that 2021 warming was relatively less pronounced compared to recent years. Even so, 2021 was still warmer than previous years influenced by La Niña,” WMO secretary-general professor Petteri Taalas said.

“The overall long-term warming as a result of greenhouse gas increases is now far larger than the year-to-year variability in global average temperatures caused by naturally occurring climate drivers.”

“The year 2021 will be remembered for a record-shattering temperature of nearly 50°C in Canada, comparable to the values reported in the hot Saharan Desert of Algeria, exceptional rainfall, and deadly flooding in Asia and Europe as well as drought in parts of Africa and South America,” Taalas added.

The WMO’s temperature result was the culmination of its analysis of six leading international datasets, combining millions of meteorological and marine observations collected by agencies including NASA, the National Oceanic and Atmospheric Administration (NOAA) and the United Kingdom’s Met Office Hadley Centre.

CSIRO research scientist, Dr Pep Canadell, said that 2021 ranking amongst the warmest years on record despite the influence of La Niña events was cause for concern – particularly given the inevitable return to warmer El Niño conditions at some point in the future.

“It is extraordinary that 2021 was among the hottest years since the beginning of the Industrial Revolution,” Canadell said.

“In the past, a La Nina year was a globally cool year, a time for a break from warmest weather. Now, a La Nina year is a globally very hot year. I am concerned of what the next super El Niño will bring, when temperatures do get seriously hot.”

Also reacting to the WMO announcement, professor Martina Doblin from the University of Technology Sydney’s Climate Change Cluster said the 2021 result was further evidence of the impacts of global warming, which was already having a damaging impact on the world’s marine ecosystems.

“Our temperature record is now long enough for scientists to be able to attribute anthropogenic warming as opposed to natural variability. We know that warming is not occurring evenly around the globe and that some people may even welcome warm seawater temperatures where they go swimming and surfing,” Doblin said.

“However, the increasing record-breaking temperatures are already inflicting harm on marine ecosystems, with well documented impacts of coral bleaching, and massive biodiversity loss during marine heatwaves.”

“How organisms will respond to more frequent, extreme and unpredictable changes in their environment remains little known, and is slated by the IPCC as urgently required if we are to manage its consequences for human society,” Doblin added.

The WMO noted the importance of considering the longer-term trends of global temperatures. Each decade since the 1980s has experienced increasingly higher average temperatures, with this trend expected to continue into future decades.

University of Queensland economist professor John Quiggin, who previously served on the board of the Climate Change Authority, said the temperature figures further highlighted the urgent need for governments to take stronger actions to cut emissions.

“Temperature fluctuations associated with the Southern Oscillation – El Nino and La Nina – and other short-term cycles cannot conceal the remorseless upward trend in global temperatures,” Quiggin said.

“This La Nina year was hotter than El Nino years only a decade ago. Despite the need for urgent action, the Australian government remains committed to doing as little as possible to reduce emissions in Australia, and nothing that would limit our exports of coal and gas.”