Susan Cobb / NOAA Global Monitoring Laboratory
The amount of carbon dioxide in Earth’s atmosphere reached 419 parts per million in May, its highest level in more than four million years, the National Oceanic and Atmospheric Administration said Monday.
After dropping last year due to lockdowns caused by a pandemic, greenhouse gas emissions have started to rise again as economies open and people return to work and travel. Newly released data on carbon dioxide levels in May shows the global community has so far failed to slow the build-up of heat-trapping gases in the atmosphere, NOAA said in its announcement.
“We add about 40 billion metric tonnes of CO2 pollution to the atmosphere per year,” Pieter Tans, senior scientist at NOAA’s Global Monitoring Laboratory, said in a statement. “If we are to avoid catastrophic climate change, the top priority must be to reduce CO2 pollution to zero as soon as possible. ”
The May measurement is the monthly average of atmospheric data recorded by NOAA and the Scripps Institution of Oceanography in an observatory at the top of the Mauna Loa volcano in Hawaii. NOAA’s monthly average from its measurements was 419.13 parts per million, and Scripps scientists calculated their average to be 418.92. A year ago, the average was 417 parts per million.
The last time the atmosphere contained similar amounts of carbon dioxide was during the Pliocene Period, NOAA said, around 4.1 to 4.5 million years ago. At that time, the sea level was 78 feet higher. The planet was on average 7 degrees Fahrenheit warmer, and large forests could have grown in what is now arctic tundra.
Homo erectus, an ancestor of humanity, emerged about two million years ago on a much cooler planet. At the time, carbon dioxide levels in the atmosphere averaged around 230 parts per million – just over half of today’s levels.
Since 1958, scientists at the Scripps Institution of Oceanography at the University of California at San Diego, and later NOAA, have regularly measured the amount of carbon dioxide in Earth’s atmosphere at a weather station at the top of the Mauna Loa. Each year, carbon dioxide concentrations increase enough to set a new record.
“We still have a long way to go to stop the rise, as each year more CO2 builds up in the atmosphere,” said Ralph Keeling, Scripps geochemist. “We ultimately need much larger and sustained cuts for longer than the COVID-related closures of 2020.”
Carbon dioxide is a greenhouse gas that stays in the atmosphere for hundreds of years. The last century, marked by a sharp increase in carbon dioxide, is almost entirely attributable to human activity, mainly the combustion of fossil fuels. The effects of climate change are already being felt, as larger and more intense hurricanes, floods, heat waves and forest fires regularly hit communities around the world.
To avoid even more dire scenarios in the future, countries must significantly reduce their emissions of carbon dioxide and other greenhouse gases, scientists say.
The United States officially joined the Paris Agreement on climate change in February. Around the same time, the United Nations warned that the emission reduction targets of the 196 member countries are largely insufficient to meet the agreement’s goal of limiting global temperatures to more than 2 degrees Celsius by the end of the century. Temperatures have already risen by around 1 degree Celsius since the mid-1800s, when the use of fossil fuels became widespread.
NOAA scientist Pieter Tans, however, suggested that the company has the tools it needs to stop emitting carbon dioxide.
“Solar and wind power are already cheaper than fossil fuels and they operate at the scales required,” Tans said. “If we take concrete action quickly, we may still be able to avert catastrophic climate change. “