The state of the climate—and of climate science

In the list of world challenges, global warming might be at once the most alarming and the most controversial. According to some predictions, climate change caused by human activity could cause mass extinction in the oceans, redraw the planet’s coastlines, and ravage world food supplies. At the same time, a significant portion of the American public questions whether global warming will really cause any major harm; many still doubt that human-driven warming is happening at all. How can we settle the debate? And can we intervene in the process or find ways to adapt to the new conditions? In conjunction with the National Science Foundation and the San Francisco Exploratorium, DISCOVER brought together four experts to discuss the reality and meaning of climate change. In a highly nuanced exchange of ideas, these researchers weighed the various scenarios and laid out a road map for navigating the warmer world to come. The conversation was moderated by DISCOVER’s editor in chief, Corey S. Powell.

Ken Caldeira: Another indication of how unusual all this is can be seen by looking at ocean chemistry. When we drive our car and carbon dioxide comes out of the tailpipe, within a year it has spread throughout the atmosphere and is integrated with the surface ocean. When carbon dioxide dissolves in seawater, it forms carbonic acid, and in high enough concentrations carbonic acid is corrosive to the shells and skeletons of many marine organisms. To measure the impact, people go out in ships and drill holes in the ocean floor, where shells of marine organisms have settled throughout geologic history. What we see is that if we continue in our current trends in burning fossil fuels, the ocean will become more acidic than it has been at any time in the past 65 million years. The last time the ocean was as acidic as it has the potential to become in the coming decades, we saw a mass extinction event.

Schneider: When you’re covering climate change, you don’t get somebody from a deep ecology group to tell you we’re near the end of the world and then somebody from the Competitive Enterprise Institute who’s going to tell you carbon dioxide is a fertilizer while forgetting about ocean acidification. If you do that, the two lowest-probability outcomes get most of the time in the media and you get this dumbed-down debate. It’s bipolar, and that’s not how system science works. There are multiple potential outcomes. What we do is whittle out the relative likelihood of each of these outcomes so we can make a value judgment about whether or not the risks are adequate to move forward. Risk is what can happen, multiplied by the probability of its happening. That’s what we call an objective or scientific assessment. We try to make the risk aspects clear and then leave the risk management where it properly belongs, which is out among the public and in the political world.

Timothy Archibald, DISCOVER, 30 June 2009. Full article.

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