Under cloud of climate change, nothing is certain

It's time to expect the unexpected. Leading environmental researchers issued that warning on 13 February at the AAAS meeting in Chicago, during a symposium to address how Earth's ecology is responding to climate change. According to the scientists, the debate on why the world is warming has ended. Now that researchers have established that humans are at least partially responsible, they said, it's critical to focus on how climate change might affect life in the 21st century and what can be done to manage the impacts.

But while society anticipates changes, it must also be aware that the predictions are shrouded with uncertainties and likely underestimated, the scientists said.

"Be prepared for surprises," said Jonathan Overpeck, director of the University of Arizona's Institute for Environment and Society. Overpeck was one of three speakers at the symposium, titled "Global Change and Paleoecology: Ecological Responses to Environmental Change."

Although scientists can forecast potential impacts of climate change, such as rises in sea level and temperature, there are unknowns and degrees of uncertainty in model projections, Overpeck said.

"There's no 'spirit of ecosystems future' to tell us what will happen," said Stephen Jackson, director of the University of Wyoming's Department of Botany. However, he added that 'ghosts of ecosystems past' do provide scientists with evidence of potential impacts.

"The good news is that climate change is nothing new. It's part of the world we live in," he said. But the bad news is that a time of climate change is not a good time to be around, Jackson said.

There will be winners and losers, he said, meaning that the changes will be good for some species and bad for others. As far as which species will benefit and which species will lose, there are "no guarantees," he said.

Although climate variation is nothing new on our planet, human activities have intensified its impact and its consequences, the speakers said.

Stacking human activity on natural variation will likely have grave ecological impacts, including the extinction of species that have survived climate change in the past.

"We're facing major obstacles," said biologist Jason McLachlan of the University of Notre Dame.

McLachlan offered a simple metaphor about the threat posed by climate change: It's like an oncoming train, with babies in carriages sitting on the tracks to represent aspects of ecology that are vulnerable to be struck.

Society must now focus on evaluating which resources and species are most at risk and develop strategies to get them further down or off the track, he said. "But keep in mind we're driving the train," he added.

He noted that humans influence the train. However, at this point the world has already committed itself to climate change and must face its challenges even if our species were to stop contributing.

High levels of carbon dioxide produced by humans will have a long lifetime in the atmosphere, said Overpeck. "We can't magically cool the Earth down," he said, noting that impacts will persist for hundreds to thousands of years.

"What we're talking about is for keeps."

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Evan Pellegrino is a NASA Space Grant intern at the Arizona Daily Star and a senior at the University of Arizona's School of Journalism. He hopes to work as a science reporter or an investigative environmental reporter at a daily newspaper. Reach him at evan462@email.arizona.edu