Global warming also occurred several million years ago due to Earth orbital changes, according to a new study.
This unexplained phenomenon has hunted some members of the scientific community for years, asking questions like what triggered the event and how it happened.
Ancient Global Warming Event
The study was published in the journal Nature Communications on September 24, wherein an international team of scientists explored the astrochronology of the Paleocene-Eocene Thermal Maximum (PETM), meaning Earth's orbital changes might had triggered an ancient global warming event 56 million years ago.
This confirmed previous evidence that global warming can also be triggered naturally.
Astrochronology is a term pertaining to the dating of sedimentary units in relation with astronomical time measurements.
In short, it is understanding the chronology of cosmic bodies, specifically through a planet's orbit and rotation.
The scientists acknowledged the continued debate on the chronology of PETM, which approximately occurred 10 million years after the Chicxulub impactor killed all non-avian dinosaurs and almost all life on Earth 66 million years ago.
This knowledge gap prevents the complete understanding of what caused the ancient warming phenomenon.
However, existing evidence reportedly suggests PETM was an "interval of global warming" during the said period characterized by a staggering four to five degrees Celsius increase in the global mean surface temperature.
This makes the historic timeline of PETM to be considered of having the highest carbon release rates since the dinosaur-killing space rock struck.
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Understanding PETM
In order to decipher PETM, the research team showed an astrochronology of a carbon isotope excursion on the Atlantic Coastal Plain.
In addition, statistical evaluation of variations in calcium content and magnetic susceptibility indicates "astronomical forcing" was involved in triggering the event.
The findings are based on methods used such as astrochronology and Earth system modeling, suggesting the start of PETM transpired during an extreme in precession of a maximum in eccentricity, favoring high temperatures, the study said.
According to Lee Kump, professor of geosciences at Penn State University in Pennsylvania, the PETM is the closest thing that we have in the geologic record that is somehow similar to what we are experiencing now and could experience in the future amid climate change, as cited by Phys.org.
Kump added that there has been a number of interests on how to better resolving this mysterious historical event and their work addresses the important questions about what caused the event and the rate of carbon emissions.
Modern Global Warming
Based on the study, it is evident that PETM was mainly triggered by natural causes, in contrast to the modern global warming, which scientists attribute to be human-induced because of greenhouse gas emissions, fossil fuel burning, and among others.
The Natural Resources Defense Council (NRDC) said that the global annual temperature has increased by slightly more than 1 degree Celsius (2 degrees Fahrenheit) since the Industrial Revolution started.
Measurements are based since the year 1880 where accurate recordkeeping started, the NRDC adds.
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