Gradual Climate Changes Could Cause Sudden Impacts

http://www.climatecentral.org/news/gradual-climate-changes-could-cause-sudden-impacts-16792

By Brian Kahn
Dec. 3, 2013

Abrupt shifts in the climate have already begun, with more possible by the end of this century according to a report released Tuesday by the National Research Council. At the same time, even gradual changes to the climate could lead to more unforeseen, sudden impacts. The report recommends creating an early warning system, instead of simply reacting to the changes.

Greenhouse gas emissions from human activities have already altered the climate. Most changes have been gradual, but the possibility of abrupt shifts concerns the scientific community.

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Tipping points from abrupt climate change became a research priority in the early 2000s. At that time, there were growing concerns that melting ice in the northern Atlantic could cause ocean circulation to come to a halt.

“Since then, knowledge has gotten better,” Richard Alley, a geoscientist at Penn State and one of the report’s authors, said in an interview. “Now we are less worried about an Atlantic shutdown.”

The new report highlights shifts that are of growing concern. The precipitous decline of summer Arctic sea ice since 1979, but particularly over the past decade, is one of the most notable sudden changes already occurring. That trend is likely to continue and have a cascade effect on ecosystems in the region as well as impacting shipping, oil and natural gas exploration, and national security.

While changes in the Arctic might be most visible, it’s changes in the globe’s lower latitudes and oceans that are of equal or greater concern, Alley said. Those areas are where the majority of people and animals live and most of the world’s food is produced.

The current rate of climate change is one most likely not seen in 65 million years. The rate of warming is likely to increase in the coming century, and that means some species, particularly those in mountainous regions, might not be able to adapt fast enough or they’ll simply run out of room to migrate.

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“By end of the century, average summers are supposed to be hotter than the hottest we’re already seeing,” he said. “Our food is already heat stressed. If we move to unprecedented levels (of warmth), what does that do for eating?”

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Slow and steady changes in the ocean’s height can cause major damage to coastal infrastructure. Alley used New York’s subway system during Superstorm Sandy as an example.

“Either the water got into it the subway or it didn’t. The difference can be billions and billions of dollars,” he said. “A pretty small sea level change can be sufficient to push you over that threshold and make a really big difference.”

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