Carbon dioxide measured at NOAA’s Mauna Loa Atmospheric Baseline Observatory peaked for 2022 at 420.99 parts per million in May, an increase of 1.8 parts per million over 2021, pushing the atmosphere further into territory not seen for millions of years. Scientists at Scripps Institution of Oceanography, which maintains an independent record, calculated a similar monthly average of 420.78 parts per million.
Carbon dioxide 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 parts per million. During that time, sea levels were between 5 and 25 meters higher than today, high enough to drown many of the world’s largest modern cities. Temperatures then averaged 7 degrees higher than in pre-industrial times, and studies indicate that large forests occupied today’s Arctic tundra.
“The science is irrefutable: humans are altering our climate in ways that our economy and our infrastructure must adapt to,” said NOAA Administrator Dr. Rick Spinrad. “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.”
Carbon dioxide 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, carbon dioxidetraps 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.
On land, higher temperatures and changing precipitation patterns cause ice caps and glaciers to melt. Within the next 25 years, many glaciers in the Alps, Rocky Mountains, the Andes could be gone as a result of climate change. High altitude plant and animal species are struggling to adapt to a warmer environment. Climate change has become a significant factor in triggering rockfalls and landslides.
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.
Prior to the Industrial Revolution in the 18th and 19th century, carbon dioxide levels were consistently around 280 parts per million for almost 6,000 years of human civilization. Since then, humans have generated an estimated 1.5 trillion tons of carbon dioxide pollution, much of which will continue to warm the atmosphere for thousands of years.
NOAA’s Mauna Loa Atmospheric Baseline Observatory, situated high on the slopes of the Mauna Loa volcano, is the global benchmark location for monitoring atmospheric carbon dioxide. At an elevation of 3,400 meters above sea level, the observatory samples air undisturbed by the influence of local pollution or vegetation, and produces measurements that represent the average state of the atmosphere in the northern hemisphere.
Charles David Keeling, a scientist with the Scripps Institution of Oceanography, initiated on-site measurements of carbon dioxide at NOAA’s weather station on Mauna Loa in 1958. Keeling was the first to recognize that carbon dioxide levels in the Northern Hemisphere fell during the growing season, and rose as plants died back in the fall, and he documented these fluctuations in a record that came to be known as the Keeling Curve. He was also the first to recognize that, despite the seasonal fluctuation, carbon dioxide levels were rising every year.
NOAA began measurements in 1974, and the two research institutions have made complementary, independent observations ever since.