Unsettled: What Climate Science Tells Us

Book Preface

The Science.” We’re all supposed to know what “The Science” says. “The Science,” we’re told, is settled. How many times have you heard it?

Humans have already broken the earth’s climate. Temperatures are rising, sea level is surging, ice is disappearing, and heat waves, storms, droughts, floods, and wildfires are an ever-worsening scourge on the world. Greenhouse gas emis-sions are causing all of this. And unless they’re eliminated promptly by radical changes to society and its energy systems, “The Science” says Earth is doomed.
Well . . . not quite. Yes, it’s true that the globe is warming, and that humans are exerting a warming influence upon it. But beyond that—to paraphrase the classic movie The Princess Bride: “I do not think ‘The Sci-ence’ says what you think it says.”

For example, both the research literature and government reports that summarize and assess the state of climate science say clearly that heat waves in the US are now no more common than they were in 1900, and that the warmest temperatures in the US have not risen in the past fifty years. When I tell people this, most are incredulous. Some gasp. And some get downright hostile.
But these are almost certainly not the only climate facts you haven’t heard. Here are three more that might surprise you, drawn directly from recent published research or the latest assessments of climate science published by the US government and the UN:

• Humans have had no detectable impact on hurricanes over the past century.
• Greenland’s ice sheet isn’t shrinking any more rapidly today than it was eighty years ago.
• The net economic impact of human-induced climate change will be minimal through at least the end of this century.

So what gives?

If you’re like most people, after the surprise wears off, you’ll wonder why you’re surprised. Why haven’t you heard these facts before? Why don’t they line up with the narrative—now almost a meme—that we’ve already broken the climate and face certain doom unless we change our ways?

Most of the disconnect comes from the long game of telephone that starts with the research literature and runs through the assessment reports to the summaries of the assessment reports and on to the media coverage. There are abundant opportunities to get things wrong—both accidentally and on purpose—as the information goes through filter after filter to be packaged for various audiences. The public gets their climate information almost exclusively from the media; very few people actually read the assessment summaries, let alone the reports and research papers themselves. That’s perfectly understandable—the data and analyses are nearly impenetrable for non-experts, and the writing is not exactly grip-ping. As a result, most people don’t get the whole story.

But don’t feel bad. It’s not only the public that’s ill informed about what the science says about climate. Policymakers, too, have to rely on information that’s been put through several different wringers by the time it gets to them. Because most government officials—and others involved in climate policy for the public and private sectors—are not themselves scientists, it’s up to scientists to make sure that non-scientists making key policy decisions get an accurate, complete, and transparent picture of what’s known (and unknown) about the changing climate, one undistorted by “agenda” or “narrative.” Unfortunately, getting that story straight isn’t as easy as it sounds.

I should know. That used to be my job.

WHERE I’M COMING FROM

I’m a scientist—I work to understand the world through measurements and observations, and then to communicate clearly both the excitement and the implications of that understanding. Early in my career, I had great fun doing this for esoteric phenomena in the realm of atoms and nuclei using high-performance computer modeling (which is also an important tool for much of climate science). But beginning in 2004, I spent about a decade turning those same methods to the subject of climate and its impli-cations for energy technologies. I did this first as chief scientist for the oil company BP, where I focused on advancing renewable energy, and then as undersecretary for science in the Obama administration’s Department of Energy, where I helped guide the government’s investments in energy technologies and climate science. I found great satisfaction in these roles, helping to define and catalyze actions that would reduce carbon dioxide emissions, the agreed-upon imperative that would “save the planet.”

But then the doubts began. In late 2013 I was asked by the Amer-ican Physical Society—the professional organization of the country’s physicists—to lead an update of its public statement on climate. As part of that effort, in January 2014 I convened a workshop with a specific objective—to “stress test” the state of climate science. In ordinary terms, that meant analyzing, critiquing, and summarizing humanity’s accumu-lated knowledge about the past, present, and future of the earth’s climate. Six leading climate experts and six leading physicists, myself included, spent a day scrutinizing exactly what we know about the climate system and how confidently we can project its future. To focus the conversation, we physicists had spent the prior two months preparing a framing doc-ument based on the UN assessment report that had just been released.1 We posed some specific and crucial questions along the lines of: Where is the data poor or the assumptions weakly supported—and does that matter? How reliable are the models that we use to describe the past and project the future? Many who’ve read the workshop transcript were struck by how successfully—and unusually—it brought out the certainties and uncer-tainties of the science at that time.2