In another indication of the profound, and perhaps irreversible, change humans are having on the planet, new research has shown that our species is pumping carbon dioxide into the atmosphere 10 times faster than at any time during the past 66 million years. This means that the last time the rate of carbon emissions was this high, dinosaurs were still walking on the face of Earth.
“In studying one of the most dramatic episodes of global change since the end of the age of the dinosaurs, these scientists show that we are currently in uncharted territory in the rate carbon is being released into the atmosphere and oceans,” Candace Major, program director in the National Science Foundation (NSF)’s Division of Ocean Sciences, which funded the research, said in a statement.
According to the study, published Monday in the journal Nature Geoscience, we — the humans — are releasing carbon at an even faster rate than what was seen during the Palaeocene-Eocene Thermal Maximum (PETM) — an event that took place approximately 56 million years ago, when a mysterious surge in atmospheric carbon sent global temperatures soaring.
New analysis of the sediment record concludes that the carbon rush at the start of the PETM extended over a period of at least 4,000 years. That translates to about 1.1 additional gigatons of carbon per year.
In contrast, humans are now emitting 10 gigatons of carbon annually.
“Because our carbon release rate is unprecedented over such a long time period in Earth’s history, it also means that we have effectively entered a ‘no-analogue’ state,” co-author Richard Zeebe from the University of Hawaii at Manoa, said in the statement. “This represents a big challenge for projecting future climate changes because we have no good comparison from the past.”
It is not yet clear what triggered the PETM event, although volcanic eruptions and methane gas releases from natural sources have been put forward as suggestions.
Be that as it may, this excess carbon resulted in a “hothouse” Earth, with global temperatures rising by nearly 5 degrees Celsius (9 degrees Fahrenheit).
Now, it seems, we are headed down the same path. And, much like the PETM event, which triggered rapid extinctions and unpredictable changes in distribution of plant and animal populations, something similar may be expected in the coming decades and centuries.
“Regarding impacts on ecosystems, the present/future rate of climate change and ocean acidification is too fast for many species to adapt, which is likely to result in widespread future extinctions in marine and terrestrial environments that will substantially exceed those at the PETM,” the researchers wrote in the study.