The US experienced its fourth-hottest year on record in 2021, while soaring levels of atmospheric methane helped push global temperatures towards all-time records, a pair of reports released on Monday show.
Underscoring the growing humanitarian and financial cost of climate change, the US National Oceanic and Atmospheric Administration (NOAA) said the death toll for weather-related disasters in the 48 mainland US states and the District of Columbia was 688 last year, more than twice 2020's tally of 262.
Year 2021 "was marked by extremes across the US, including exceptional warmth, devastating severe weather and the second-highest number of billion-dollar weather and climate disasters on record," NOAA said.
Twenty separate weather incidents cost the US $1 billion or more, the second-most billion-dollar events recorded in a calendar year behind 2020, which saw 22, the agency said.
Meanwhile in Europe, the Copernicus Climate Change Service said a substantial rise in atmospheric methane levels helped propel global temperatures in 2021 towards the highest ever recorded.
Copernicus published a report determining that last year was the fifth-warmest in the 52-year European record, slightly hotter than 2015 and 2018.
The last seven years rank as the hottest on record, with 21 of the 22 warmest years occurring since 2000.
Copernicus said atmospheric methane increased by a record amount last year, to 1,876 parts per billion.
The supercharged greenhouse gas with more than 80 times the initial warming impact of carbon dioxide comes from natural sources, such as swamps and termites, as well as human activity that includes oil and gas infrastructure, cow emissions, rice production and landfills.
The multiple sources make it difficult to say with precision which are responsible for the overall spike, but there are new ways to track some previously hard-to-detect methane emitters.
The jump in global atmospheric methane comes as satellite and ground-based sensing has rendered the gas newly visible to cameras. In one recent example, a pipeline-safety measure taken for highway construction in northeast Texas in November led to methane release at an hourly rate equal to a year of CO₂ emissions from 2,500 cars.
Responding to the NOAA report, Rachel Cleetus, policy director and lead economist for the Climate and Energy Program at the Union of Concerned Scientists, called the statistics "sobering."
"The devastating toll and trauma imposed by extreme weather and climate disasters have, and continue to, hit some people harder than others with communities of colour, low-income communities, and communities that have endured multiple disasters often bearing the brunt of its impacts," she said.
NOAA reported that 2021 ranked as America's fourth-warmest year in a 127-year period of record, with average temperatures of 12.5 Celsius in the contiguous US. December 2021 was the warmest on record – 3.75c above average.
The US is the world’s biggest CO₂ polluter historically, and shows no sign of abating despite White House ambition to halve 2005 emissions by the end of the decade.
A preliminary analysis of last year's emissions suggests the US is moving in the opposite direction, with greenhouse gas emissions rising by 6.2 per cent — a faster rate than gross domestic product growth of 3.8 per cent, according to research firm Rhodium Group.
The result marks a 17 per cent leap from 2020 emissions, propelled by increased coal-burning and freight hauling.
Other scientific groups, including NASA, the UK Met Office and Berkeley Earth, maintain climate records that go back to the 19th century and are expected to release their 2021 results later this month.
Agencies contributed to this report.