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Climate Changing at Fastest Pace Since the Age of Dinosaurs

By Terrell Johnson (Weather.com) - August 6, 2013

Earth’s climate is changing more quickly today than at any time since the extinction of the dinosaurs some 65 million years ago, according to a new report by a pair of Stanford University researchers in the latest issue of the journal Science.

Over the next century, the pace of climate change is expected to continue to pick up speed, the report warns, which could lead to a rise in average annual temperatures of 5 to 6 Celsius degrees (about 9 to 11 Fahrenheit degrees) by 2100.

If that happens as forecast, the report says, many plant and animal species in a wide range of terrestrial ecosystems will need to be able to adapt rapidly to changing conditions in their environment — or migrate quickly toward the North and South poles — in order to survive.

Velocity of Climate Change

“The planet has not experienced changes this rapid in 65 million years,” Christopher Field, one of the report’s co-authors, said in an interview with ClimateWire. “Humans have never seen anything like this.”

Field, a senior fellow with the Stanford University Woods Institute and the director of the global ecology department at the Carnegie Institution for Science, wrote the report with Noah Diffenbaugh, also a Stanford Woods Institute senior fellow and an associate professor of environmental earth system science.

Their findings come from a wide-ranging review of scientific literature on how climate change affects ecosystems around the planet, and how projections for the next century compare with past changes in Earth’s climate.

Already, they note, a certain amount of global warming is “baked into the system,” as a result of past greenhouse gas emissions. But the degree to which climate change warms the planet by the end of this century still depends largely on what humans do between now and then, they add.

An increase in global temperatures of just 1.5 Celsius degrees by 2100 would mean a pace of climate change that’s 10 times faster than anything seen since the dinosaurs’ extinction — and that’s with “aggressive mitigation efforts” (i.e., major efforts to reduce greenhouse gas emissions) of the kind that the world’s industrialized nations so far have shown little willingness to undertake.

But a rise of 5 to 6 Celsius degrees would mean a warming pace that’s 50 to 100 times faster than any seen in the past 65 million years, ClimateWire explains.

“We know from past changes that ecosystems have responded to a few degrees of global temperature change over thousands of years,” Diffenbaugh said in a press release, noting that after the last ice age ended about 20,000 years ago, plants and animals moved into the areas that had been covered by glacial ice.

“But the unprecedented trajectory that we’re on now is forcing that change to occur over decades,” he added. “That’s orders of magnitude faster, and we’re already seeing that some species are challenged by that rate of change.”

Field and Diffenbaugh also projected to 2100 the velocity of climate change, or the distance that plant and animal species would need to migrate toward cooler climates in order to live in temperatures like the ones in which they currently live.

Worldwide, species threatened by warming temperatures would need to move toward the poles (or to higher elevations) by at least one kilometer per year, they found, which works out to roughly a yard per day. While farmers can shift their crops and animals can more easily migrate, it’s tougher for plant species — especially at the speed our warming planet will require.

“Maple trees are not good at moving,” Field told ClimateWire, adding, “You don’t have forests moving over long distances very, very fast.”

While it is “highly likely” that the current trajectory of climate change will continue to intensify in the coming decades, the report adds, the ultimate velocity of climate change is not yet a foregone conclusion.

“Although many Earth system feedbacks are uncertain, the greatest sources of uncertainty — and greatest opportunities for modifying the trajectory of change — lie in the human dimension,” the authors write in the report.

“The rate and magnitude of climate change ultimately experienced by terrestrial ecosystems will be mostly determined by the human decisions, innovations, and economic developments that will determine the pathway of GHG [greenhouse gas] emissions.”