This past decade is also the hottest on record, according to the provisional State of the Global Climate report, published by the World Meteorological Organisation (WMO), the UN’s voice on weather, climate and water. All six hottest years have happened since 2015.
The report is based on contributions from dozens of international organisations and experts but the climate extremes in 2020 have been painfully clear.
There has been an unprecedented wildfire season in the western United States, while blazes have consumed vast areas of Australia, Siberia and South America.
Death Valley in California hit 54.4C (129.9F) on 16 August, believed to be the highest temperature ever recorded.
Devastating cyclones and typhoons impacted south-east Asia and the Indian subcontinent. Severe flooding has displaced millions of people in East Africa and the Sahel region of western and north-central Africa, along with south Asia, China and Vietnam.
A record-breaking Atlantic hurricane season struck in 2020, including unprecedented back-to-back category-4 hurricanes in Central America last month.
The health and economic stability of millions has been impacted, compounding the threat already posed by the coronavirus pandemic. And despite the near global lockdown, greenhouse gas levels continue to rise, locking in future heating of the planet.
“The average global temperature in 2020 is set to be about 1.2C above the pre-industrial (1850-1900) level. There is at least a one in five chance of it temporarily exceeding 1.5C by 2024,” says WMO secretary-general Professor Petteri Taalas.
“This year is the fifth anniversary of the Paris Agreement on climate change. We welcome all the recent commitments by governments to reduce greenhouse gas emissions because we are currently not on track and more efforts are needed.”
A core ambition of the 2015 Paris Agreement among nations has been to pursue efforts to limit global heating to 1.5C.
Prof Taalas notes that previous years of record heat have coincided with an El Nino, the complex weather system that happens around every five years in the Pacific Ocean, as it happened in 2016.
But 2020 has seen a La Nina event, which has an overall cooling effect on global temperatures.
The La Nina “has not been sufficient to put a brake on this year’s heat”, says Prof Taalas.
The WMO assessment, based on five global temperature datasets, currently places 2020 as the second warmest for the year to date, following 2016 and ahead of 2019.
However the difference between the warmest three years is marginal, and the rankings could shift once the full picture of 2020 is available.
Among the most striking evidence has been the temperature increases in the Siberian Arctic, where it has been 5C above average.
In June, the highest-ever temperature was recorded inside the Arctic Circle when the town of Verkhoyansk hit 38C (100.4F), fuelling the most active wildfire season in two decades.
Prof Dave Reay, chair in carbon management at the University of Edinburgh, describes the state of the global climate as “parlous”.
“These annual updates of deteriorating planetary health always make for bleak reading; this year’s is a full red alert. Surging heat, intensifying droughts and rampant wildfires all speak of the acute impacts of climate change in 2020,” he says.
“They also warn of the chronic undermining of global carbon sinks – the oceans, trees and soils around the world – that is underway. Throw yet more emissions and warming at them and they will rip the Paris Climate goals from our grasp forever. The year ahead will be defined by our recovery from Covid-19, the centuries ahead will be defined by how green that recovery actually is.”
The WMO findings make for dire reading on the health of the planet: ocean heat is at record levels, with more than 80 per cent of the global oceans experiencing a marine heatwave in the past year as it alleviates much of the impact of the climate crisis.
Much of the ocean experienced at least one “strong” marine heatwave at some point in 2020, according to satellite monitoring of sea surface temperature. There was an extreme marine heatwave in the Laptev Sea, off the coast of Siberia, that lasted from June to October.
The oceans are becoming more acidic as they absorb excess carbon dioxide (CO2), sucking up about a quarter of the annual carbon emissions that humanity pumps into the atmosphere.
This has consequences for marine life: the more acidic the oceans, the faster that organisms with shells and skeletons made of calcium carbonate dissolve, affecting their ability to grow and reproduce. This in turns impacts the entire health of the food chain.
Since the mid-1980s, the Arctic has warmed at least twice as fast as the global average. Arctic sea ice reached its annual minimum in September, the second lowest, based on 40 years of satellite records. Arctic sea ice in July and October 2020 was the lowest on record. The vast losses of ice mass from the ice sheets is also driving sea level rise.
Katie White, director of advocacy and campaigns at WWF, says that 2020 has shown that “we are breaking records that should not be broken”.
“The whole world now needs to act ahead of next year’s UN climate conference and as hosts, we in the UK must show leadership by urgently raising our own ambitions. It’s imperative that we act now – for people, nature and our planet,” she adds.
The provisional State of the Global Climate report is based on temperature data from January to October. The final report will be published in March 2021.