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Tuesday, December 08, 2015

"Magical Thinking": Will Staying Below 2C Save the Earth?

The politicians love to think that staying below at 2°C rise in average global temperatures over the years 1800-present will somehow “save the planet.” If you believe that, you have yet to realize politicians lie with the regularity of sunrise.

538 points out why The 2-Degree Warming Limit Is Arbitrary And Beside The Point:

Two degrees became the default goal almost by happenstance. The number originated with Yale economist William Nordhaus, who back in the 1970s published a paper suggesting that a rise in global temperature of more than 2 degrees would represent temperatures hardly seen over the past several hundred thousand years. Nordhaus’s number was based on preliminary intuition, though climate data has confirmed that during the past 100,000 years, global mean temperatures have rarely, if ever, reached much higher than 2 C above those around 1800.

Two degrees isn’t a magic number that will somehow hold catastrophe at bay. We have already nearly arrived at a 1-degree temperature rise, and as Reto Knutti and his colleagues argue in this week’s Nature Geoscience, the 2-degree goal is not a scientific one. Although the 2-degree limit is often referred to as a “guardrail,” Knutti told me, “there’s no scientific research to show that 2 degrees of warming is safe.” And there’s a reason for that — science alone can’t determine what’s an unacceptable level of danger.

The best analogy for this, he said, is speed limits on roads. “You could quantify the risk of dying at certain speeds, but even if you could quantify that perfectly, it would still not tell us what speed limit is appropriate — that’s a judgment call,” he said. Set a universal speed limit of 30 mph, and the roads are safer. But now it takes a long time to get places. On the other hand, if the speed limit is set very high, people can get to their destinations faster — but the roads become more dangerous. Science alone can’t determine the right middle ground between these two extremes.

The 2-degree limit is similarly a compromise between costs, benefits and risks. Set the warming limit too high, and it may not inspire the appropriate urgency. Set it too low, and it may be so strict that countries don’t sign on to the agreement because they’re afraid their economies will become too stunted if they have to stop using fuels that produce emissions. Given the social, political, and economic factors at play, science can’t provide a one-size-fits-all solution. Climate change affects regions and countries differently, and it’s difficult to precisely predict at which temperatures and greenhouse gas emission levels climate change will become unbearable. Residents of the Persian Gulf region may cry uncle sooner than those living in northern climates, and island states will feel the change before landlocked countries.

Determining where to draw the line requires judgment calls as well as science. It’s a question of priorities. For instance, Knutti said, the world could ask itself, “Do you care or not if the polar bear goes extinct?” There are reasons polar bears might matter: They’re icons of the fight against global warming, and their extinction might be a harbinger of a cascade of habitat changes that could ripple down the food chain. But on the other hand, setting a temperature limit to save the polar bear may not allow for a developing country to hit its GDP target. Which matters more to the world at large?

There’s not always agreement about what the priorities should be, obviously. Developed nations made their wealth with fossil fuels, and they aren’t going to give them up if that would require relinquishing the lifestyles they’ve become accustomed to. Even staunch environmentalists tend to go green only as long as it’s convenient.

Meanwhile, poor countries would like to develop their economies and lift their standards of living. But doing so without the fossil fuels that got the rest of the world there is an expensive challenge, especially as they face more extreme weather events because of climate change.