A new study by researchers at the University of Wisconsin-Madison reveals that the Earth is moving into a future that closely resembles conditions existing about 50 million years ago on the planet.
The research, which was recently published in the Proceedings of the National Academy of Sciences, shows that humans have taken just two centuries to reverse a long-term cooling trend going back at least 50 million years.
According to the study, Earth's climate by 2030 is likely to resemble the mid-Pliocene, which goes back more than 3 million years in geologic time; by 2150, the climate will be comparable to the Eocene, a warm and mostly ice-free period from 50 million years ago.
The study’s lead author Kevin Burke conducted the research as a graduate student in the lab of paleoecologist John ‘Jack’ Williams, professor of geography at the University of Wisconsin-Madison, and builds on the work of Williams, which was published in 2007.
Burke says that humans are moving into uncharted territory at an extremely rapid pace, reversing a planetary cooling trend in a matter of a couple of centuries. Though all of the species on Earth today had an ancestor that survived the Eocene and the Pliocene epochs, it’s not known whether they can adapt to these rapid changes.
Earth's continents were closer during the Eocene epoch when global temperatures averaged 13 degrees Celsius warmer than they are today.
Dinosaurs were extinct and the first mammals were spreading across the globe.
During the Pliocene epoch from about 3 million years ago, North and South America joined tectonically, the Himalayas formed, land bridges allowed animals to migrate across continents and temperatures were 1.8 to 3.6 degrees Celsius warmer.
Collaborating 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, Burke and Williams compared future climate projections set forth by the Intergovernmental Panel on Climate Change Fifth Assessment Report to several periods of geologic history including the Early Eocene, the mid-Pliocene, the Last Interglacial (129 to 116 thousand years ago), the mid-Holocene (6,000 years ago), the pre-industrial era (before A.D. 1850) and the early 20th century.
The researchers used Representative Concentration Pathway 8.5 (RCP8.5), a future climate scenario in which greenhouse gas emissions are not mitigated, and RCP4.5, a scenario where greenhouse gas emissions are moderately reduced.
Climate simulations were based on three different models: the Hadley Centre Coupled Model version 3, the Goddard Institute for Space Studies ModelE2-R and the Community Climate System Model.
Using these scenarios and models, the researchers found that the Earth's climate will most closely resemble the mid-Pliocene by 2030 (under RCP8.5) or 2040 (under RCP4.5).
In the absence of any mitigation of greenhouse gas emissions, Earth’s climate will continue to warm till it achieves Eocene-like conditions by 2150. Over time, the Earth will experience rising temperatures and precipitation, melting ice caps and more temperate climate near the poles. Conditions that do not have any known geologic or historical precedent will be seen in eastern and south-eastern Asia, northern Australia and the coastal Americas.
Williams, who has been working in this field for about 25 years, says that the Earth is experiencing the harmful effects of climate change today in terms of deaths, damage to property, and intensified fires and storms.
While initiatives such as switching from fossil fuels toward more sustainable and carbon-free energy sources are helping, more needs to be done, he observed.