According to a new review of 27 climate models, scientists say the global climate is likely to experience a warmth as great as any in the last 65 million years, only much, much faster. According to the study published today in Science, the Earth’s land temperature will rise by 4 degrees Celsius (7.2 degrees Fahrenheit) from pre-industrial levels by 2100 if we continue on our current emissions trajectory.
“What is perhaps most noteworthy is the rate of change,” says co-author Noah Suresh Diffenbaugh with Stanford University. “For instance, the rapid global warming event that occurred some 55 million years ago was as large as these warming projections, but that event occurred over many thousands of years, not a mere century.”
If it occurs, the temperature rise would be at least 10 times faster than anything seen since the mass extinction of the dinosaurs, creating unknown impacts on the Earth’s species and ecosystems.
“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.”
More warming, the scientists warn, will certainly intensify severe weather and make today’s hottest summers the norm. The scientists write that this warming over such a short span could make it impossible for many species to adapt.
“Species and ecosystems will encounter not only a range of climate conditions that is potentially different from any in the past but also the broader conditions of the Anthropocene , in which human actions either dominate or strongly influence a wide range of Earth system processes,” the researchers write.
Even if a species is capable of outrunning global climate change, it may not be able to in the face of habitat destruction, pollution, invasive species, and overexploitation. The scientists note that the combination of rapid global warming and human ecological impacts “will
present terrestrial ecosystems with an environment that is unprecedented in recent evolutionary history.”
Greenhouse gas emissions from burning fossil fuels, deforestation, and industrial agriculture have already warmed the Earth around 0.8 degrees Celsius (1.44 degrees Fahrenheit) over the last hundred years. The warming to date has led to rising sea levels, worsening heatwaves, melting Arctic sea ice, and vanishing glaciers among other impacts.
Still, the scientists note that a number of uncertainties underpin the path of future warming, including feedback processes like the carbon cycle and clouds. However, the largest of the uncertainties is how much additional fossil fuels will human civilization burn? While some warming is unavoidable given past emissions, the worst impacts could still be eluded.
“The future of the planet lies in our hands,” notes co-author Chris Field also with Stanford.
Top: The change in annual temperature projected for the late 21st century using simulations from 27 global climate models. The change is calculated as the 2081-2100 mean minus the 1986-2005 mean. Bottom: The velocity of climate change required to maintain the current annual temperature should the late-21st-century climate change occur. The velocity is calculated foreach location by identifying the closest location in the future climate that has the same annual temperature as the starting location has in the present climate.
Image courtesy of Noah Diffenbaugh.
CITATION: N.S. Diffenbaugh and C.B. Field. Changes in Ecologically Critical Terrestrial Climate Conditions. Science. 2013.
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