World faces narrow window to cut carbon emissions — study

Source: Amanda Reilly, E&E reporter • Posted: Tuesday, February 9, 2016

Humans have only a small window to zero out carbon dioxide emissions that could lead to changes affecting the globe for tens of thousands of years, according to new research published today.

The study in the journal Nature Climate Change warned that the climate change debate has focused on time frames that are too short, largely ignoring long-term changes to the ecology and geology of the world.

The only way to avert these long-term changes, the authors wrote, is by shaping a new energy system with net-zero or net-negative carbon dioxide emissions within the next few decades.

“Much of the carbon we are putting in the air from burning fossil fuels will stay there for thousands of years — and some of it will be there for more than 100,000 years,” Peter Clark, an Oregon State University paleoclimatologist and lead author, said today in a statement. “People need to understand that the effects of climate change on the planet won’t go away, at least not for thousands of generations.”

Researchers from the United States, Canada, Germany, Switzerland, France, Australia and the United Kingdom participated in the study.

The authors contend that researchers and policymakers have overwhelmingly focused on relatively short-term shifts linked to climate change, changes in the last 150 years and their effects up to the year 2100.

Using computer models, the research team projected how human actions will affect the globe over the next 10,000 years.

It found that humans have only a few decades to halt “potentially catastrophic climate change that will extend longer than the entire history of human civilization thus far.”

“Our greenhouse gas emissions today produce climate-change commitments for many centuries to millennia. It is high time that this essential irreversibility is placed into the focus of policymakers,” said Thomas Stocker, a climate modeler at the University of Bern in Switzerland. “The long-term view sends the chilling message [about] what the real risks and consequences are of the fossil fuel era.”

The team predicted that sea levels will rise by 25 meters with warming of 2 degrees Celsius and 50 meters with warming of 7 C, over a time frame of the next several centuries to millennia. On the low end, 122 countries will see at least a tenth of their population affected by higher sea levels.

The latest report by the U.N. Intergovernmental Panel on Climate Change found that sea levels could rise by 1 meter by 2100.

“It takes sea-level rise a very long time to react — on the order of centuries,” Clark said. “It’s like heating a pot of water on the stove; it doesn’t boil for quite a while after the heat is turned on — but then it will continue to boil as long as the heat persists.”

According to the authors, studies that focus only on near-term risks, as well as the economic practice of discounting future climate impacts, tend to play down the future, more severe impacts.

While short-term emission reduction targets — such as the ones nations committed to in the recent Paris climate deal — are “important,” the authors said, only a “complete transformation” of the globe’s energy system within the next few decades will halt severe impacts.

They called for a “fourth industrial revolution” entailing changes in energy, land use and agriculture.

“We are making choices that will affect our grandchildren’s grandchildren,” said Harvard University geology professor Daniel Schrag, a co-author of the study. “We need to think carefully about the long-term scales of what we are unleashing.”