Earth’s atmosphere now holds more carbon dioxide than it has in millions — possibly tens of millions — of years, according to new data from the National Oceanic and Atmospheric Administration (NOAA) and scientists at the University of California San Diego.
For the first time in recorded history, global average CO₂ concentrations exceeded 430 parts per million (ppm) in May. That’s a new all-time high, rising by more than 3 ppm from last year.
Climate scientists say the spike highlights the world’s failure to curb emissions of the heat-trapping gas, a key driver of global warming.
“Another year, another record,” said Ralph Keeling, a climate scientist at UC San Diego’s Scripps Institution of Oceanography. “It’s sad.”
Fast-rising CO₂
Carbon dioxide, produced mainly by burning fossil fuels, lingers in the atmosphere for centuries. Its buildup leads to rising global temperatures, melting ice caps, rising sea levels, and more extreme weather.
Atmospheric CO₂ has risen sharply since preindustrial times due to human activity. Decades ago, the idea of breaching 400 ppm seemed far off. That mark was reached in 2013.
Now, with levels hitting 430 ppm, scientists warn the world could see 500 ppm within 30 years.
“Uncharted territory”
Keeling said Earth has not seen this much carbon dioxide in over 30 million years, when the climate was radically different — and humans didn’t exist.
“It’s changing so fast,” Keeling told NBC News. “If humans had evolved in such a high-CO₂ world, there would probably be places where we wouldn’t be living now. We probably could have adapted, but we built our society around yesterday’s climate.”
Tracking the climate signal
CO₂ levels are plotted on the Keeling Curve, named after Keeling’s father, Charles David Keeling, who began daily measurements in 1958 at Hawaii’s Mauna Loa Observatory.
The curve shows a sharp rise since the Industrial Revolution — the clearest signal of human-caused climate change.
In May, Scripps recorded an average of 430.2 ppm, while NOAA’s monitoring lab reported 430.5 ppm. Both are the highest monthly averages ever recorded.
Scientists monitor these levels as a critical gauge of Earth’s climate health.
“They’re telling you about your whole system health with a single-point measurement,” Keeling said. “It’s a holistic measurement from a very simple set of data.”
About The Author
