Stanford University climate researchers warn that the likely rate of climate change over the next century will be 10 times faster than the rate of any climate shift in the past 65 million years, meaning the planet will undergo one of the largest changes in climate since the dinosaurs went extinct.
Noah Diffenbaugh, an associate professor of environmental Earth system science, and Chris Field, a professor of biology and of environmental Earth system science at the Stanford Woods Institute for the Environment, report in the journal Science that if the climate change trend continues at the current pace, it will place stress on terrestrial ecosystems around the world and that adaptation to a world with a new climate will be necessary many species to survive.
Earth has gone through periods of global warming and cooling in the past, but most current climate research fingers anthropogenic factors in facilitating greater climate change.
"There are two key differences for ecosystems in the coming decades compared with the geologic past," Diffenbaugh said in a statement. "One is the rapid pace of modern climate change. The other is that today there are multiple human stressors that were not present 55 million years ago, such as urbanization and air and water pollution."
For their latest research, Diffenbaugh and Field conducted a "targeted but broad" review of scientific literature on aspects of climate change that can effect ecosystems and compared recent climate observations against the geological record.
"We know from past changes that ecosystems have responded to a few degrees of global temperature change over thousands of years," said Diffenbaugh. "But the unprecedented trajectory that we're on now is forcing that change to occur over decades. That's orders of magnitude faster, and we're already seeing that some species are challenged by that rate of change."
The researchers analyzed two dozen climate models to describe climate outcomes from today to the end of the century, finding that heatwaves and heavy rainfall are expected to become more frequent and more severe.
At the high end of the climate scenarios models predict that greenhouse gas emissions will push up annual temperature averages by 2 to 4 degrees Celsius by 2046-2065. At that rate, the models predict the hottest summer of the last 20 years to occur ever other year. By the end of the century, should the high-end greenhouse gas emissions remain unchecked, the models predict a temperature increase in the Northern Hemisphere of 5-6 degrees Celsius warmer than today's averages, hot enough to make the hottest summer of the last 20 years to new annual norm.
"It's not easy to intuit the exact impact from annual temperatures warming by 6 C," Diffenbaugh said. "But this would present a novel climate for most land areas. Given the impacts those kinds of seasons currently have on terrestrial forests, agriculture and human health, we'll likely see substantial stress from severely hot conditions."
Diffenbaugh said some climate change is already "baked into the system" by greenhouse emissions already released and that even if every new power plant or factory in the world produced zero emissions there would still be a climate impact.
He noted that humans have the ability to slow -- or increase -- the pace of climate change towards the end of the century. As more people gain more access to more energy, their quality of life will improve but their increased energy demand will likely hasten global warming, but improvements in technology may lower emissions associated to energy production and transportation.
"There's no question that a climate in which every summer is hotter than the hottest of the last 20 years poses real risks for ecosystems across the globe," Diffenbaugh said. "However, there are opportunities to decrease those risks, while also ensuring access to the benefits of energy consumption."