CO2 Levels Surging Toward Highest In More Than 200 Million Years


There is no denying humanity’s indelible contribution to climate change. After millions of years of relative stability, just a few hundred years of greenhouse gas emissions will charge the Earth and its creatures toward unprecedented warming. The finding is published in the journal Nature Communications.

If unabated in the next 100 to 200 years, carbon dioxide (CO2) concentrations in Earth's atmosphere will rise to the highest since the Triassic 200 million years ago. If CO2 continues to rise even further, the next 200 to 300 years will surge to a warming state without geological precedent in the last 420 million years.

For the study, the team gathered over 1,241 estimates of atmospheric COconcentrations from 112 published studies to create a record dating back 420 million years. Since a direct measurement of ancient CO2 concentrations is not possible, researchers rely on indirect “proxies” to construct a record. This included published data on fossilized plants, the carbon isotopic composition of ancient soil samples, and the boron isotopic composition of fossil shells.

The cumulation of these proxies reveal a startling truth: While Earth’s climate has fluctuated in the past, the current speed of climate change is uniquely swift. 

Living Ginkgo leaf (left) and fossil (right). Density of stomata in such leaves is a proxy of atmospheric CO2 in past. Dana Royer

Atmospheric CO2 levels depend on a variety of factors, including volcanism, metamorphism, organic carbon weathering, human activity, and more. There have, of course, been fluctuations in the climate record throughout history, but the climate had remained relatively stable for millions of years until the Industrial Revolution. 

Before the Industrial Revolution, carbon dioxide concentrations were around 280 parts per million (ppm). Today, that figure has risen to 400 parts per million. By 2250, that could surge past 2,000 ppm if no efforts are made to mitigate emissions – levels not seen since the Triassic (220-200 million years ago), with the climate reaching a state of warmth not seen since the Devonian (around 400 million years ago). The increase in temperature is partly due to the addition of a future hotter Sun.

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