A group of scientists has determined that humanity is reversing a trend of long-term planetary cooling, which goes back at least 50 million years, according to a study published in the journal PNAS.
“We are moving towards very dramatic changes in an extremely fast time frame, reversing a global cooling trend in a matter of centuries,” warned one of the authors of the report, Jack Williams, of the University of Wisconsin-Madison.
According to the team’s projections, it is expected that by 2030 the climate of the Earth will resemble that of the middle Pliocene, which dates back more than 3 million years in geological time.
Likewise, without reductions in our greenhouse gas emissions, Earth’s climates in 2150 could be compared to the warm Eocene, an almost ice-free era that characterized the world 50 million years ago.
“If we think about the future in terms of the past, where we are going is an unexplored territory for human society,” said the lead author, Kevin Burke, a researcher at the same university.
All species on Earth today had an ancestor that survived the Eocene and Pliocene, but it remains to be seen if humans and the flora and fauna with which we are familiar can adapt to these rapid changes.
“The rate of accelerated change seems to be faster than anything else the planet has experienced before,” the scientists wrote.
The new study is based on the work that Williams and his colleagues published for the first time in 2007, which compared future climate projections with historical climate data from the early 20th century.
“We can use the past as a criterion to understand the future, which is very different from everything we have experienced in our lives,” Williams argued.
During the Eocene, the continents of the Earth were grouped and global temperatures averaged about 23.4 °F more than at present times.
The dinosaurs had recently become extinct and the first mammals, such as whales and ancestral horses, were spreading all over the world.
The Arctic was occupied by swamp forests like those found today in the southern United States.
In the Pliocene, North and South America joined tectonically, the climate was arid and the Himalayas were formed, among other landmarks.
At that time, temperatures were between 3.2 and 6.5 °F higher than today.