The cause of global warming shows no signs of slowing down, as the carbon dioxide that traps heat in Earth’s atmosphere has risen to record highs during the annual spring peak, at one of the fastest rates on record, officials announced Monday.
Carbon dioxide levels in the air are now the highest in more than 4 million years due to the burning of oil, coal and gas. The last time the air had similar amounts was during a less hospitable greenhouse on Earth before human civilization took root, scientists said.
The National Oceanic Atmospheric Administration announced that carbon dioxide levels measured in Hawaii in May averaged 424 parts per million. That’s 3 parts per million more than the May average last year and 51% higher than the pre-industrial level of 280 ppm. It is one of the largest annual increases in carbon dioxide levels from May to May on record, behind only 2016 and 2019, which had jumps of 3.7 and 3.4 parts per million.
“For me as an atmospheric scientist, that trend is very concerning,” said Arlyn Andrews, leader of NOAA’s greenhouse gas monitoring group. “CO2 emissions not only continue to increase despite efforts to reduce emissions, but they are also rising faster than they were 10 or 20 years ago.”
Emissions used to rise by maybe 1 part per million a year, but now they are rising twice or even three times that, depending on whether there is an El Nino, Andrews said.
“The relentless increase in CO2 in the atmosphere is incredibly concerning, if not completely predictable,” said Brown University climate scientist Kim Cobb, who was not part of the study.
Carbon dioxide levels are rising so that each year is higher than the previous one. However, there is a seasonal cycle of carbon dioxide so that it reaches its highest saturation point in May. That’s because two-thirds of the world’s land is in the Northern Hemisphere and plants suck carbon dioxide from the air, so during late spring and summer, carbon dioxide levels drop until they start to rise again in November, Andrews said.
Carbon dioxide levels rise more during El Nino climate cycles because the northern hemisphere is drier. There’s an El Nino brewing. That 3.0 rise could be a sign of an El Nino bump, she said.
There are two main ways to track greenhouse gases. One is to monitor what comes out of chimneys and tailpipes, but about half of that is absorbed by the oceans and land, Andrews said.
The other way is to measure how much carbon dioxide is in the air. NOAA and partner agencies measure around the world. Hawaii has the longest history of direct measurements and is home to the Scripps Institution of Oceanography’s Keeling Curve, which has tracked atmospheric carbon since 1958, when the measurement peaked at 317.5 in May. Emissions have since increased by about 33%.
“Current emissions will remain in the atmosphere for thousands of years, and they will continue to trap heat energy near the Earth’s surface for thousands of years,” Andrews said.
Therefore, “we are still dealing with CO2 in the atmosphere that was emitted in the early to mid-20th century,” Jason Furtado, a meteorology professor at the University of Oklahoma who was not part of the monitoring teams, said in an email. . “That is why we need to see emissions fall in order to reverse climate change. And even if/when we reduce CO2 emissions, it will take some time before the climate system reacts.”
This year NOAA had a reading complication.
NOAA and the Scripps Institution have two different monitors with slightly different sizes. Scripps measured 423.8 parts per million and often runs slightly below NOAA. Both have been on the remote Mauna Loa volcano for decades, but last November’s eruption cut off power to the NOAA monitor and it has been out of action since then. NOAA located another at Mauna Kea volcano, 21 miles away.
Scripps got their Mauna Loa site working and placed one on Mauna Kea, and their data shows that Mauna Kea is an accurate substation for Mauna Loa, Andrews said.
Many activists and scientists are calling for a return to levels of 350 parts per million.
“CO2 is now higher than at any time in the past 4 to 4.5 million years when the atmosphere was about 7 degrees Fahrenheit (3.9 degrees Celsius) warmer and sea levels were 5 to 25 meters (16 to 82 feet) higher,” Andrews said.
Temperatures were higher with a similar amount of carbon dioxide in the air because carbon dioxide retains heat for so long, and millions of years ago, the buildup of carbon dioxide was much more gradual, allowing heat to build and ice to melt to raise seas, scientists said.
“We are definitely at levels unseen in human civilization,” Furtado said. “People are conducting a massive experiment on Earth’s climate system by burning carbon, and the results are turning out not to be great for many people on this planet.”
Follow AP’s climate and environment coverage at https://apnews.com/hub/climate-and-envirment
Follow Seth Borenstein on Twitter at @borenbears
The Associated Press’ climate and environmental coverage is supported by several private foundations. Read more about AP’s climate initiative here. The AP is solely responsible for all content.