The last time the Earth was as warm as it is now may have been more than 100,000 years ago, a time when the sea level was also 20 to 30 feet higher. We're not underwater yet, because sea level rise lags well behind temperature rise, and we're only beginning to see the impacts of extreme weather. But a new discussion paper argues that in order to prevent future catastrophe, the world will have to do a lot more than politicians have planned so far.
"There's a misconception based on the Paris climate summit, where all the government leaders clap each other on the back, as if some great progress has been made," lead author James Hansen, from the Columbia University Earth Institute, said on a press call. "But you look at the science, and it doesn't compute. We're in fact not doing what is needed."
The paper hasn't been peer-reviewed yet. Hansen, who argues that we're running out of time, rushed to get something into print that could also be useful in the climate lawsuit he's party to with his granddaughter. In the lawsuit, 21 children are suing the federal government. They argue that by not taking enough action to protect the future climate, the government is violating their constitutional rights (in April, a federal judge ruled that the case could proceed; a second judge is now considering certifying that opinion).
In part, the paper is meant to explain the state of the current science to non-scientists like a judge and jury. The authors calculate that by August 2016, the global mean temperature in the 12 months prior was 1.3 degrees Celsius higher than it was in the pre-industrial period. The growth of the three major greenhouse gases—carbon dioxide, nitrous oxide, and methane—is also speeding up.
In Paris, global leaders agreed to make plans to keep global warming below 2 degrees Celsius, with a stretch goal of keeping it below 1.5 degrees. But either goal would result in higher temperatures than has occurred over the Holocene epoch that sustained human life for more than 11,000 years. The paper argues that if temperatures stay that high for too long, it will spur "feedbacks" (like methane released from melting permafrost) that will push temperatures further out of control.
In order to make the climate stable by the end of the century, the paper suggests that emissions need to steeply drop by about 6% a year.
"Technically, it's still possible to solve the climate problem and stabilize climate by the end of the century, but that has two essential requirements," Hansen says. "That would be making the price of fossil fuels honest by having a simple across the board rising carbon fee, which would spur the development of alternative clean energy. Also, I think the government has to be supporting the development of clean energy in a very substantial way, which it's not doing now."
Some current scenarios would require massive use of carbon capture technology in the future—from catching carbon from biofuel plants to sucking it out of the air—which other studies have optimistically estimated would cost hundreds of trillions of dollars, and may not necessarily be feasible. If emissions are reduced more quickly, we could use cheaper systems of carbon capture now, including planting forests and using biochar in soil.
Since the government isn't acting quickly enough, Hansen has turned to the courts. "The court has a role to play," he says. "Not to get involved in the detailed description of solutions to the climate but just forcing the other branches of the government to sit down and come up with a plan that would reduce emissions at the rate that the science dictates is essential. Or young people will be handed a system where the climate is running out of control and they can't do anything about it."
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