Humans May Reverse a 50 Million Year Climate Trend After Just Two Centuries

50 million years ago, the world started cooling. The industrial revolution marked the beginning of the end of this climate trend.

Dec 10 2018, 8:00pm

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If the world’s greenhouse gas emissions are left unchecked, the Earth’s climate will be similar to how it was 50 million years ago by 2150. This period, known as the Eocene, was characterized by an ice-free Earth and an arid climate across most of the planet.

This is the conclusion of new research published today in Proceedings of the National Academy of Sciences that used leading climate models and archaeological data to compare Earth’s future with its past.

“If we think about the future in terms of the past, where we are going is uncharted territory for human society,” Kevin Burke, graduate student in paleoecology at the University of Wisconsin and lead author of the study, said in a statement. “We are moving toward very dramatic changes over an extremely rapid time frame, reversing a planetary cooling trend in a matter of centuries.”

According to the predictions made by Burke and his colleagues, the world won’t have to wait until 2150 to see dramatic climate change that resembles the Earth’s ancient past. Burke and his colleagues predicted that by 2030 the Earth’s climate will be similar to how it was 3 million years ago during the Pliocene. To put this in perspective, this is right about the time our human ancestors were first learning to make stone tools.

All three models showed that Earth’s climate would resemble that seen about 3 million years ago by either 2030 or 2040.

The Earth’s 4 billion year history is defined by cyclic warming and cooling periods, but these cycles normally occur over the course of tens of millions of years. Yet as Burke and his colleagues report, humans will have managed to effectively reverse a 50 million year cooling trend within a matter of a few centuries. The slow pace of Earth’s natural transitions means that some species are able to adapt and survive the changes, but it’s unclear whether plants and animals will be able to survive such a rapid transition.

To make these predictions, Burke and his colleagues examined two different climate scenarios with three different state-of-the-art climate simulations. One of these scenarios is known as Representative Concentration Pathway 9.5 (RCP8.5.) This is a worst case scenario in which we do not reduce our greenhouse gas emissions at all. The other is known as RCP4.5 and represents a future in which we moderately reduce greenhouse gas emissions.

In both of these scenarios, all three models showed that Earth’s climate would resemble that seen about 3 million years ago by either 2030 (RCP8.5 scenario) or 2040 (RCP4.5 scenario.) In the case of the RCP4.5 scenario, the Earth’s climate stabilized at these conditions, which would be characterized by temperatures about 3 to 6 degrees Fahrenheit higher than today.

In the RCP8.5 scenario, however, the Earth’s climate begins to resemble conditions found about 50 million years ago by 2100 and by 2150 these conditions are generalized across the entire planet. Based on fossil evidence, this time in Earth’s history—known as the Eocene—was about 23 degrees Fahrenheit warmer on average. This would spell the end of Earth’s arctic regions, which would come to resemble swamp lands instead.

Burke and his colleagues also found that the rapid climate change induced by the RCP8.5 scenario would introduce “novel” climates across nearly 10 percent of the Earth. These local climates would be unprecedented for those locations.

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While the predictions of Burke and his colleagues are alarming, things needn’t turn out like their models. Burke suggested that climate-friendly policies, like switching to renewable energy, could push reality closer to the RCP4.5 scenario. Unfortunately, politicians like Donald Trump continue to question the reality of climate change or the dangers it poses.

“Many species will be lost and we live on this planet,” John Williams, a paleoecologist at the University of Wisconsin, said in a statement. “These are things to be concerned about, so this work points us to how we can use our history and Earth’s history to understand changes today and how we can best adapt.”