Earth's CO2 levels highest in over 3 million years, US scientists say

The Covid-19 pandemic did nothing to slow the root cause of global warming. In fact, the level of carbon dioxide in the Earth's atmosphere is now higher than it has been in at least 3.6 million years, US scientists announced Wednesday. – File photo: AP

The Covid-19 pandemic did nothing to slow the root cause of global warming.

In fact, the level of carbon dioxide in the Earth's atmosphere is now higher than it has been in at least 3.6 million years, US scientists announced Wednesday.

At that time, sea levels were as much as 78 feet (23.77m) higher, the average temperature was 7 degrees Fahrenheit higher than in pre-industrial times, Greenland was mostly green, and Antarctica had trees.

Overall, levels of carbon dioxide (CO2) and methane — the two most important greenhouse gases — continued their unrelenting rise in 2020 despite the economic slowdown caused by the pandemic, according to scientists from the National Oceanic and Atmospheric Administration.

"Human activity is driving climate change," Colm Sweeney of NOAA's Global Monitoring Laboratory said in a statement released Wednesday. "If we want to mitigate the worst impacts, it's going to take a deliberate focus on reducing fossil fuels emissions to near zero — and even then we'll need to look for ways to further remove greenhouse gases from the atmosphere."

The burning of fossil fuels such as coal, oil and gas releases greenhouse gases such as carbon dioxide and methane, which has caused the temperature of Earth's atmosphere to rise to levels that cannot be explained by natural causes, scientists say.

In the past 20 years, the world's temperature has risen about two-thirds of a degree, NOAA said.

"We're completely certain that the increase in CO2 is warming the planet," Kate Marvel, a climate scientist at NASA, told the Capital Weather Gang this week. "I'm even more certain CO2 causes global heating than I am that smoking causes cancer. The world is already more than 2 (degrees) warmer than it was before the Industrial Revolution."

Carbon dioxide is called a greenhouse gas because of its ability to trap solar radiation and keep it confined to the atmosphere.

It is invisible, odourless and colourless yet is responsible for 63% of the warming attributable to all greenhouse gases, according to NOAA's Earth System Research Laboratory in Colorado.

The global surface average for carbon dioxide was 412.5 parts per million (ppm) in 2020, rising by 2.6 ppm during the year. The global rate of increase was the fifth-highest in NOAA's 63-year record.

The pandemic-fuelled economic recession was estimated to have reduced carbon emissions by about 7% in 2020, NOAA said. Without the economic slowdown, the 2020 increase would have been the highest on record, according to Pieter Tans, senior scientist at NOAA's Global Monitoring Laboratory.

NOAA's analysis also showed the annual increase in atmospheric methane — a far more potent greenhouse gas than carbon dioxide when it comes to global warming — for 2020 was 14.7 parts per billion, the largest annual increase recorded since measurements began in 1983.

"Although increased fossil emissions may not be fully responsible for the recent growth in methane levels, reducing fossil methane emissions are an important step toward mitigating climate change," said NOAA research chemist Ed Dlugokencky. – USA Today/Tribune News Service