"There is more carbon dioxide in Earth's atmosphere than at any time in the past four million years, as the world's continued dependence on fossil fuels keeps humanity hurtling toward a 'global catastrophe,' officials at the National Oceanic and Atmospheric Administration warned on Friday"

NOAA reports its Mauna Loa Atmospheric Baseline Observatory in Hawaii measured CO2 levels averaging 420.99 parts per million (ppm) in May, an increase of 1.8 ppm over levels at this time last year, while scientists at the San Diego-based Scripps Institute of Oceanography, which also tracks atmospheric CO2, calculated a monthly average of 420.78 ppm.

"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 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" toward climate resiliency and action, he added.

As NOAA explains:

“CO2 pollution is generated by burning fossil fuels for transportation and electrical generation, by cement manufacturing, deforestation, agriculture, and many 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.

Impacts to the world's oceans from greenhouse gas pollution include increasing sea surface temperatures, rising sea levels, and an increased absorption of carbon, which makes sea water more acidic, leads to ocean deoxygenation, and makes it more difficult for some marine organisms to survive.”

Before the Industrial Revolution, CO2 levels registered around 280 ppm for the entire history of human civilization, or about 6,000 years. Since then, it's estimated that human activity has released more than 1.5 trillion tons of the planet-heating greenhouse gas.

"CO2 levels are now comparable to the Pliocene Climatic Optimum, between 4.1 and 4.5 million years ago, when they were close to, or above 400 ppm," notes NOAA. "During that time, sea levels were between five and 25 meters higher than today, high enough to drown many of the world's largest modern cities. Temperatures then averaged 7°F higher than in pre-industrial times, and studies indicate that large forests occupied today's Arctic tundra."

Adequately reducing global CO2 emissions would require a dramatic shift in human activity—especially by the world's wealthiest 1%, who according to a September 2020 study by Oxfam emit more than twice as much CO₂ as the poorest 50% of humanity.

"It's depressing that we've lacked the collective willpower to slow the relentless rise in CO2," said Ralph Keeling, who runs Scripps' program at the mountaintop observatory. "Fossil fuel use may no longer be accelerating, but we are still racing at top speed towards a global catastrophe."

Pieter Tans, senior scientist at NOAA's Global Monitoring Laboratory, said that "carbon dioxide is at levels our species has never experienced before—this is not new."

"We have known about this for half a century, and have failed to do anything meaningful about it," he added. "What's it going to take for us to wake up?" 

-Brett Wilkins, Common Dreams