The amount of heat-trapping carbon dioxide in the atmosphere had passed a major milestone – more than 50% higher than pre-industrial times – and is at levels not seen since millions of years ago when the Earth was a greenhouse ocean was flooded planet, federal scientists announced Friday.
The National Oceanic and Atmospheric Administration said its old monitoring station in Mauna Loa, Hawaii, averaged 421 parts per million carbon dioxide for May when the critical greenhouse gas reaches its annual peak. Before the industrial revolution in the late 1800s, carbon dioxide levels were 280 parts per million, scientists said, so humans significantly changed the atmosphere. Some activists and scientists want a level of 350 parts per million. Industrial carbon dioxide emissions come from coal, oil, and gas combustion.
The gas levels continue to rise while they should fall, scientists say. This year’s carbon dioxide levels are nearly 1.9 ppm more than a year ago, a slightly larger jump than from May 2020 to May 2021.
“The world is trying to reduce emissions, and you just don’t see it. In other words, if you measure the atmosphere, you don’t see anything happening in terms of change,” said NOAA climate scientist Pieter Tans, who tracks global greenhouse gas emissions for the agency.
Outside scientists said the numbers point to a serious problem of climate change.
“If you look at this incremental but sustained increase in CO2 emissions from year to year, it’s like watching a train moving towards you in slow motion along the track. It’s terrifying,” said University of Wisconsin-Madison climate scientist Andrea Dutton. “If we stay on the track with a last-minute plan to get out of the way, we could die of heat stroke on the track before it even happens. But to us.”
University of Illinois climate scientist Donald Wuebbles said that without reducing carbon pollution, “we will see more and more harmful levels of climate change, more heat waves, more floods, more droughts, more major storms, and higher sea levels.”
Due to the slowdown in the pandemic, global carbon emissions fell slightly in 2020 but recovered last year. Tans said that both changes were small compared to the amount of carbon dioxide pumped into the atmosphere each year, especially considering that carbon dioxide stays in the atmosphere for hundreds to a thousand years.
The world puts about 10 billion tons of carbon into the air every year, much of it being pulled down by oceans and plants. Therefore, May is the peak for global carbon dioxide emissions. As they grow, plants in the Northern Hemisphere begin to suck up more carbon dioxide in the summer.
NOAA said carbon dioxide levels are now about the same as they were 4.1 to 4.5 million years ago in the Pliocene era when temperatures were 7 degrees (3.9 degrees Celsius) hotter, and sea levels were 16 to 82 feet (5 to 25 meters) was higher than it is now. South Florida, for example, was completely underwater. These are conditions that human civilization has never known.
The reason it was much warmer and the seas were higher at the same carbon dioxide levels millions of years ago as they are today is that in the past, the natural increase in carbon dioxide levels was much more gradual. With carbon stuck in the air for hundreds of years, temperatures rose for extended periods and stayed there. The ice sheets of Antarctica and Greenland melted over time, causing sea levels to soar and the Earth to darken and reflect less heat from the planet, Tans and other scientists said.
Scientists at the Scripps Institution of Oceanography calculated the levels differently based on time and average, putting the May average at 420.8 ppm, slightly lower than NOAA’s figure.
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