On May 9, the Mauna Loa Observatory in Hawaii measured for the first time a daily average carbon dioxide (CO2) concentration surpassing 400 parts per million. In other words, out of every million air molecules, an average of 400 were CO2. The last time CO2 concentrations were this high was probably during the Pliocene geological epoch, during 5 to 2.5 million years ago. CO2, of course, warms the planet.
Before contemplating this, I’d like to make a point about history and science education. Science has discovered the history of humans, animals, the planet, and the universe during an unimaginably longer time than just the past 10,000 years considered in standard history courses. University and high school general history courses should spend at least a week on pre-human history (birth of the planet, origin of life, and evolution up to the ape-human separation 6 million
years ago), followed by a week on early human history (the 20-plus human species since 6 million years ago, emphasizing forbears such as Ardipithecus, Australopithecus, and Homo erectus). Humankind’s geological, biological, anthropological and historical ignorance causes immense grief in this turbulent world, and is an anachronism today. We will not understand who we are until our education is appropriate to the scientific age in which we live.
A May 9 National Geographic news article puts the new CO2 benchmark into perspective. CO2 levels, along with changes in Earth’s orbit, are the main drivers of long-term climate. Throughout the many ice ages that alternated with warm “interglacials” during the past 2.5 million years, and up until the industrial age just 250 years ago, CO2 levels ranged between 180 and 300 ppm.
Going back much further, during the Eocene some 50 million years ago there were alligators in northern Greenland living in swampy forests similar to those in our southeastern states today. This warm period, nicknamed “Hothouse Earth,” can only be explained by CO2 that was belched from volcanoes, causing CO2 concentrations two to ten times higher than today.
During the next 45 million years, CO2 levels dropped as atmospheric CO2 was deposited in limestone while volcanic activity subsided. By the time of the Pliocene, 5 to 2.5 million years ago, CO2 levels had dropped to under 500 ppm. Some time toward the end of the Pliocene, CO2 levels probably crossed the 400 ppm mark and headed further downward. It was the end of the long hothouse, and the beginning of a slow slide into the Ice Ages. As our ancestors were climbing down from the trees in Africa, the planet was 3 to 7 degrees warmer than it is today and there were camels and little ice in northern Greenland. The 400 ppm CO2 concentration created a climate very different from today’s. Because there was so little ice, sea levels were 30 feet to 130 feet higher than today. Even the lower estimate would flood land inhabited by 75 million Americans.
For further perspective, consider the interglacial period a mere 400,000 years ago when CO2 levels are known (via Antarctic ice core measurements) to have peaked at 290 ppm, far below today’s 400 ppm. The evidence is strong that some of the ice sheets of Greenland and Antarctica melted, raising sea levels
30 feet above today’s levels.
CO2 concentrations are rising every year by more than 2 ppm.
Continued high CO2 levels could cause the climate to switch gears into something resembling the Pliocene. The geological record tells us the system is quite sensitive to CO2. Experts believe we’re nearing the threshold for losing the Greenland and West Antarctic ice sheets. CO2 has increased from 280 to 400 ppm, and temperatures by 1 degree, in the geological instant since 1750. Even the strongest efforts to limit emissions cannot prevent an increase to 450 ppm, implying another 1,000 years of high CO2 levels.
The only solution is to soon stop emissions, and that will not happen until we put a price on carbon. The fossil fuel industry is spending a fortune on propaganda and politics to convince us they should be allowed to ignore the enormous damage they cause. Putting a price on carbon can be easy and nearly free. Simply enact a revenue-neutral carbon tax that is refunded to Americans as an income tax reduction. Industry must begin to incorporate their environmental and social overhead into their own cost of doing business, or the environment, business, and society will collapse.
ART HOBSON IS A PROFESSOR EMERITUS OF PHYSICS AT THE UNIVERSITY OF ARKANSAS.