The Blog

Why Did Global Warming "Tip"? (Part I)

How has the issue finally managed to go mainstream, so that even President Bush now seems on the verge of feeling its urgency?
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** Note: "Part II" of this post is now online.**

In my recent conversations with peers in the science policy world (read "fellow geeks"), the same question has come up repeatedly of late: Why did global warming "tip"? How has the issue finally managed to go mainstream, so that even President Bush now seems on the verge of feeling its urgency?

With this weekend's coming Live Earth concert -- a truly global mega-event that will likely prompt even greater awareness of the climate crisis -- the question becomes even more pertinent. We seem to be watching history in the making, which makes it ever more critical to understand how we got here.

When the subject of global warming's "tipping point" arises, it's never long before someone brings up the high profile public intellectual role that has been played by Al Gore (with a lot of help from Hollywood). Yet while it would be foolish to deny Gore's significance, I rather suspect that much as global warming itself is caused by many different greenhouse gases and not just carbon dioxide, so the issue's development has been driven by many factors rather than a single individual or event. In fact, while global warming has indisputably risen in profile of late, that hardly means we have yet achieved adequate awareness of its urgency in the United States.

To see what might be driving the current rash of attention to climate change, it helps to begin with data compiled by Matthew Nisbet, a professor at the School of Communication at American University. Taking two agenda-setting newspapers, The New York Times and The Washington Post, as broad indicators of media coverage patterns, Nisbet used the Lexis-Nexis database to examine how much attention these two outlets have paid to global warming over more than two decades, with a particular emphasis on events that may have driven coverage levels. The resultant figure looks like this:

(For a higher resolution version of the graphic, Download file.)

As you can see, levels of media coverage have generally risen over time, but there have been many valleys accompanying the peaks that have lifted us to the current moment. In the late 1980s, the issue saw its first media spike in association with NASA climatologist James Hansen's famous summer of 1988 testimony before Congress -- which was soon followed in 1990 by the first scientific report from the United Nations' Intergovernmental Panel on Climate Change (IPCC). But the rise in attention could not be sustained: Coverage soon started to decline, even as a new and in some ways troubling pattern set in.

From the early 1990s and on, media coverage would be driven not by increasing scientific knowledge about global warming (and its human causation), but rather, by dramatic political events and controversies: The 1992 U.N. Rio Conference; the 1997 Kyoto Protocol; President George W. Bush's 2001 withdrawal from it. By contrast, the 1995-1996 release of the second IPCC assessment -- a highly significant scientific moment, as this was the first time the global scientific community pronounced that the fingerprint of human greenhouse gas emissions had become detectable in global temperatures -- represented a low moment for media attention.

Nevertheless, Nisbet's data plainly show that the volume of attention to global warming surged towards historic highs beginning in 2005 and especially in 2006 (a rise that has likely continued in 2007). Yet unlike in the case of the previous peaks, Nisbet finds it difficult to attribute this development to any single event or cause. Rather, a multitude of factors seem in play here, which we can now seek to untangle and identify.

2005 saw several key developments, including a focus on global warming at the G8 meeting in Gleneagles, a record temperature year globally, and most of all, Hurricane Katrina. The latter sparked unprecedented levels of discussion of the relationship between global warming and hurricanes in particular. Indeed, when you look at more New York Times and Washington Post data compiled by Nisbet, and published in my new book Storm World: Hurricanes, Politics, and the Battle Over Global Warming, you see a meteoric rise in attention to this single issue in the climate debate:

Much as has occurred with the devastating drought in Australia, Katrina -- a single dramatic event -- seems to have helped galvanize public and political attention to climate change. This is of course rather awkward from a scientific standpoint, in that for both Katrina and for the drought, any direct causal attribution to global warming remains deeply problematic or even impossible.

The movie poster for Al Gore's An Inconvenient Truth features a smokestack belching forth a hurricane, dramatizing how these storms became new icons of climate change. And with that film's release, Gore became, even more than before, the climate issue's top messenger and communicator, while Hollywood -- through the release of Gore's film and, later, by awarding him an Oscar -- blazoned a message about the urgency of addressing climate change. As Gore himself understood -- and as is also plainly evident when we contemplate the Live Earth concert -- using entertainment media to communicate such a message was critical because their broad reach extends far beyond the narrower audiences who tune in regularly to science or policy coverage.

And even as Gore reached many people who may never before have grasped the importance of global warming, in November of 2006 the Democrats regained control of Congress for the first time in over a decade and proceeded to invite Gore to testify before them. With control of congressional committees, Democrats could at last set the political agenda and include global warming as a prominent part of it. Whereas under Oklahoma Republican James Inhofe the Senate Environment and Public Works Committee had served as a forum for the debunking of climate change, under Barbara Boxer of California it has become a driving force for addressing the problem.

There can be little doubt, then, that rising levels of media coverage of global warming over the past several years have helped the issue reach an apparent tipping point. Yet we can't simply point to the total volume of attention -- we must also consider the content of press coverage over time. Several seeming shifts in the narratives that journalists have been telling may have further contributed to progress on the issue, and in my next post -- "Why Did Global Warming "Tip," Part II -- I will break those down and analyze them. Stay tuned....

(Note: This post draws upon the contents of a public lecture entitled "Speaking Science 2.0" that I have delivered on numerous occasions with American University professor Matthew Nisbet.)