Carbon dioxide, or CO2, measured at NOAA’s Mauna Loa Atmospheric Baseline Observatory in Hawaii peaked for 2022 at 421 parts per million (ppm) in May, “pushing the atmosphere further into territory not seen for millions of years,” experts said.

Prior to the Industrial Revolution - and for almost 6,000 years of human civilization - CO2 levels were consistently around 280 ppm.

Since that period of profound technological transformations, which began in the 18th century, scientists estimate that humans have generated around 1.5 trillion tons of CO2 pollution, much of which will continue to warm the planet for thousands of years to come.

The announcement was made by scientists from NOAA - a federal agency that provides science and service to protect the Earth’s natural resources - and from the Scripps Institution of Oceanography at the University of California San Diego.

“The science is irrefutable: humans are altering our climate in ways that our economy and our infrastructure must adapt to,” NOAA Administrator Rick Spinrad said in a statement.

“We have known about this for half a century, and have failed to do anything meaningful about it,” he said. “What’s it going to take for us to wake up?”

“We can see the impacts of climate change around us every day. The relentless increase of carbon dioxide measured at Mauna Loa is a stark reminder that we need to take urgent, serious steps to become a more Climate Ready Nation,” he added.

According to NOAA, carbon dioxide pollution is generated by the burning of fossil fuels for transportation and electrical generation, as well as cement manufacturing, deforestation, agriculture and other practices.

“Along with other greenhouse gases, CO2 traps heat radiating from the planet’s surface that would otherwise escape into space, causing the planet’s atmosphere to warm steadily, which unleashes a cascade of weather impacts, including episodes of extreme heat, drought and wildfire activity, as well as heavier precipitation, flooding and tropical storm activity,” the agency said.

“It’s depressing that we’ve lacked the collective willpower to slow the relentless rise in CO2,” said Ralph Keeling, a renowned geochemistry professor who runs the Scripps program at Mauna Loa. “Fossil-fuel use may no longer be accelerating, but we are still racing at top speed towards a global catastrophe,” he added.

Pieter Tans, senior scientist with the Global Monitoring Laboratory, shared Keeling’s frustration, saying that the high levels of CO2 in the atmosphere are nothing new - but still, the world has so far refused to act accordingly.

“We have known about this for half a century, and have failed to do anything meaningful about it,” he said. “What’s it going to take for us to wake up?”