A new study published in the Proceedings of the National Academy of Sciences says humans are reversing a long-term cooling trend racing back at last 50 million years, in just two centuries.
The study predicts that by 2030 Earth’s climate will resemble that of the mid-Pliocene, going back more than three million years in geologic time.
Without reductions in greenhouse gas emissions, Earth’s climates by 2150 could compare to the warm and mostly ice-free Eocene, an epoch that characterized the globe 50 million years ago, the study said.
The University of Wisconsin research project, funded by the National Science Foundation and Wisconsin Alumni Research Foundation, was also reported online at EurekAlert, the website of the American Association for the Advancement of Science.
All species on Earth today had an ancestor that survived the Eocene and the Pliocene, but whether humans and the flora and fauna humans today are familiar with can adapt to these rapid changes remains to be seen. The accelerated rate of change appears to be faster than anything life on the planet has previously experienced, researchers said.
The study builds on work paleoecologist John “Jack” Williams, a professor of geography on the UW-Madison campus, and his colleagues first published in 2007, comparing future climate projections to historical climate data from the early 20th century.
During the Eocene, Earth’s continents were packed closer together and global temperatures averaged 23.4 degrees Fahrenheit warmer than they are today. Dinosaurs had recently become extinct and the first mammals, like ancestral whales and horses, were spreading across the planet. The Arctic had swampy forests like those found now in the southern United States.
During the Pliocene, North and South America were joined tectonically, the climate was arid, land bridges allowed animals to spread across continents and the Himalayas formed. Temperatures were between 3.2 and 6.5 degrees Fahrenheit warmer than today.
For this study Williams and lead author Kevin Burke worked with colleagues at the University of Bristol, Columbia University, University of Leeds, NASA Goddard Institute for Space Studies and the National Center for Atmospheric Research to examine similarities between future climate projections as set forth by the Intergovernmental Panel on Climate Change Fifth Assessment Report and several periods of geologic history.
“In the roughly 20 to 25 years I have been working in the field, we have gone from expecting climate change to happen, to detecting the effects, and now, we are seeing that it’s causing harm,” Williams said. “People are dying, property is being damaged, we’re seeing intensified fires and intensified storms that can be attributed to climate change. There is more energy in the climate system, leading to more intense events.”
