Carbon dioxide (CO2) levels surged past the 415 ppm level this Saturday, May 11, for the first time in human history. Strong global economic growth combined with a weak El Niño event in the tropical Pacific have caused CO2 levels to rise very rapidly over the past year to 415.39 ppm this Sunday.
The last time in geologic history that CO2 levels were this high was 3 to 5 million years ago in the Pliocene when sea levels were 16 to 131 feet higher. scripps.ucsd.edu/…
As atmospheric carbon dioxide levels rise, scientists look back four million years for answers on what to expect from climate
The Pliocene is the geologic era between five million and three million years ago. Scientists have come to regard it as the most recent period in history when the atmosphere’s heat-trapping ability was as it is now and thus as our guide for things to come.
Recent estimates suggest CO2 levels reached as much as 415 parts per million (ppm) during the Pliocene. With that came global average temperatures that eventually reached 3 or 4 degrees C (5.4-7.2 degrees F) higher than today’s and as much as 10 degrees C (18 degrees F) warmer at the poles. Sea level ranged between five and 40 meters (16 to 131 feet) higher than today.
Obviously, sea levels 131 feet higher would be a catastrophe for human civilization, but sea level rise is a lagging effect of climate change because the global oceans have a vast store of deep cold water that will take hundreds of years to reequilibrate with global atmospheric conditions. The rate of CO2 rise in the present has the potential to create rapid climate change which will drive ecological shifts, extinction events, chaotic weather, and instability in crop growth and food production.
Richard Norris, a geologist at Scripps Institution of Oceanography, UC San Diego, said the concentration of CO2 is one means of comparison, but what is not comparable, and more significant, is the speed at which 400 ppm is being surpassed today.
“I think it is likely that all these ecosystem changes could recur, even though the time scales for the Pliocene warmth are different than the present,” Norris said. “The main lagging indicator is likely to be sea level just because it takes a long time to heat the ocean and a long time to melt ice. But our dumping of heat and CO2 into the ocean is like making investments in a pollution ‘bank,’ since we can put heat and CO2 in the ocean, but we will only extract the results (more sea-level rise from thermal expansion and more acidification) over the next several thousand years. And we cannot easily withdraw either the heat or the CO2 from the ocean if we actually get our act together and try to limit our industrial pollution–the ocean keeps what we put in it.”
Once heat and CO2 go into the oceans it takes thousands of years for them to cycle back out after CO2 levels are stabilized. For practical purposes carbon in the oceans is “forever” just like the slogan “Diamonds are Forever”. When you go to the beach or the coast this summer take a hard look. In only a few decades the most vulnerable beaches and coastlines will either retreat or submerge. That process will continue for hundreds of years because of the carbon that we have already put in the atmosphere.