The current epoch of human-made carbon dioxide emission can only be compared to the Paleocene-Eocene Thermal Maximum (PETM), a time period 55.6 million years ago. In this ancient era, the planet was considerably hot, even more than what it is today. Also, the carbon dioxide level was soaring high, which caused the planet to have a temperature higher by another 5 to 8 degrees Celsius. This extraordinary carbon dioxide level was absorbed by the oceans, thus, initiating chemical reactions which caused waters to become highly acidic and killed many marine species.
The massive carbon dioxide emission during the PETM was known to scientists for quite some time, but what caused this extraordinary CO2 level had remained unknown so far. One of the prominent theories was that volcanoes had sparked waves of carbon dioxide release for thousands of years.
Now, a recent study solidifies the volcanic eruption theory and it also compares the CO2 release in the ancient period with that of the current epoch of human-induced climate change. The study was published in PNAS (Proceedings of the National Academy of Sciences). According to the estimates of the study, human activities are outpacing the CO2 emission at a rate three to eight times faster than what the volcanic eruptions might have done. The consequences of it, obviously, are catastrophic to all species both in water and on land.
Commenting on it, Laura Haynes, the lead author of the study said, “The research is directly relevant to today. We want to understand how the earth system is going to respond to rapid CO2 emissions now. The PETM is not the perfect analog, but it’s the closest thing we have. Today, things are moving much faster.”
The researchers of the study took resort to the foraminifera, the amoeboid organisms that survive in deep seawater. Each foram creates a shell primarily made up of calcium in process of their reproduction. The researchers cultured the tiny amoeba in the lab in a condition that resembled the highly acidic ocean situation during the PETM. They recorded the way the organism took up boron into the shells during development and reproduction. The researchers then compared this boron uptake data of the lab-cultured foraminifera with the fossilized foraminifera from the Pacific and Atlantic Ocean floor. These fossils are from the PETM era.
This allowed them to estimate the signature carbon isotope with specific carbon source and led them to infer that the massive CO2 of the PETM was sourced at volcanic eruptions that probably were centered in and around what is today Iceland.
These eruptions were periodic and could release as much as 14.9 quadrillion (1000 trillion) metric tonnes of CO2 to the oceans. Previous estimates say that the carbon pulses lasted for 4,000 to 5,000 years. With the CO2 increased extraordinarily, oceans absorbed more and more of it and became highly acidic in return.
When compared with the CO2 emissions of the present time, caused by human activities, a grim picture emerges. Atmospheric CO2 levels have soared from 280 ppm (parts per million) in the 1700s to a staggering 415 ppm today, and it is nowhere close to stopping in the near future.
Another devastating consequence of the human-induced CO2 emission is that it is released rapidly. If CO2 is absorbed by the oceans slowly, marine life could adapt to it, but when this takes place very rapidly, the situation can prove catastrophic.