Last week I asked a few reporters and scholars why it is that a major paper in Nature last week on hurricanes and global warming received almost no media coverage whereas another paper released last summer received quite a bit more. Andy Revkin raised the issue on his blog which stimulated many more responses. With this post I’d like to report back on what I’ve heard, and what I’ve concluded, at least tentatively, on the role of the media in the climate debate.

First, there are a wide range of explanations for the differences in media coverage of the two papers. Here is a summary of what I heard (warning: not all explanations are consistent with each other):

*The media is biased toward sensational stories, and Vecchi/Soden was not sensational.

*The relevant media was distracted by the Bali climate meeting.

*The relevant media was distracted by the AGU meeting.

*The relevant media had an interest in stories that added to pressure to act on climate change in Bali.

*The media has (recently) begun to downplay research that suggests uncertainty in climate science.

*Nature did not promote the Vecchi/Soden paper, whereas NCAR aggressively promoted Webster/Holland.

*Vecchi/Soden buried their main message, so the news value was hard to see.

*The hurricane/climate change issue is “s/he said-s/he said” and not interesting.

*Hurricane season is over.

One question I asked of several people is the apparent paradox between the recent “balance as bias” thesis which holds that skeptical voices are given too much play in debate over climate change with the claims from several people I spoke to that the media tends to favor alarming stories in the climate debate. The best answer I got to this came from a reporter:

In general, news coverage favors the sensational rather than the mundane. For example, there were tons of stories this year on the arctic sea ice extent. Next year, if the sea ice doesn’t set a record, the coverage will be less by orders of magnitude.

However, within stories on global warming, there is a great pressure to be balanced. So if we have scientists saying human activity is causing the melting, there’s a desire to represent another viewpoint, no matter how much in the minority it may be.

So there’s an overall bias for sensationalism (or alarmism, when it comes to global warming). The simple reason is this attracts eyeballs. But within stories there’s an effort for balance.

To test this out the hypothesis of a general bias against skeptical voices I searched Google News for references (2004 to present) to “climate change” and “hurricanes” for both “William Gray” who advocates no discernible effect of global warming on hurricanes and “Kerry Emanuel” who advocates a very strong effect. There were 268 stories quoting Emanuel and 297 quoting Gray. This would suggest that, on the hurricane issue at least, there is no indication that the media has disfavored skeptical voices. These data don’t say much about the media favoring the sensational, as Gray’s presence in news stories might just be “balance” in a sensationalized story. More work would need to be done to say anything on that.

Looking to the academic literature Mullainathan and Shleifer (2002, full cite and link below) provide the best piece of research that I have seen on media bias. They focus on ideological biases and also what they call “spin.” which is the same thing as favoring (or creating) sensational stories as suggested above. They suggest that (emphasis added):

. . . competition is an important argument for free press: despite the ideological biases of individual news suppliers, the truth comes out through competition. We show that, with Bayesian readers, this is indeed the case: competition undoes the biases from ideology. With readers who are categorical thinkers, however, the consequences of competition are more complex. We show that, in the absence of ideology, competition actually reinforces the adverse effects of spin on accuracy. Not only do the media outlets bias news reporting, but the stories reinforce each other. As each paper spins stories, it increases the incentives of later outlets to spin. This piling on of stories means non-ideological competition worsens the bias of spin. Moreover, spin can exacerbate the influence of one-sided ideology. When the first news outlet that uncovers the story is ideological and later ones are not, the first one sets the tone and later ones reinforce this spin. This can explain why and how inside sources leak information to news outlets: their principal motivation is to control how the story is eventually spun.

Our theory of news reporting falls between two extremes. The traditional view is that readers demand, and media outlets supply, pure information about political and economic markets, and thereby facilitate better consumer and voter choice (Coase 1974, Besley and Burgess 2001, Besley and Prat 2002, Djankov et al. 2002, Stromberg 2001, Dyck and Zingales 2002). The opposite but also plausible view, pursued by Mencken (1920) and Jensen (1976), sees the media as entertainment, with no obvious grounding in reality. The perspective of this paper is that media outlets provide neither unadulterated information, nor pure entertainment. News outlets may be biased for ideological reasons. And consumers, while not desiring pure entertainment as might be the case with sensational or human interest stories, do indirectly affect news content because of how they process information. So for reasons of ideology news outlets may bias information to please their owners, and for reasons of consumer psychology they may bias the information to please their readers.

These results have significant implications for media accuracy. They explain, in particular, how the media in the aggregate are likely to get to the bottom of a news story with significant ideological dimension. Ideological diversity serves as a safeguard against spin. Our results are consistent with Richard Posner’s (1999) highly favorable assessment of the press in the coverage of the Clinton affair. Our results also show why media bias is most severe in the cases where no or little ideological diversity bears on the story, such as the investigation of Wen Ho Lee. In this case, the bias comes from spin, and spin causes the followers to pile on. Competition among media outlets is not a solution to the problem of spin – indeed, it makes the problem worse. Our paper makes the case for extreme ideological diversity in the media – in such diversity lies the best hope against spin.

If these findings are anywhere close to the mark, then they offer a powerful counterargument to the “balance as bias” thesis. The climate issue is characterized by a wide range of ideological perspectives, and it seems hard to justify why any of those perspectives should not be represented by the media. That means reporting on a wide range of political perspectives and the justifications for those views offered by those holding those perspectives, even if the reporter, or the vast majority of scientists or other groups, happens to disagree with either the politics or justifications. Where there is diversity balance is not bias, but bias is bias.

S. Mullainathan and A. Shleifer. 2002. Media Bias, NBER WORKING PAPER SERIES, Working Paper 9295 NATIONAL BUREAU OF ECONOMIC RESEARCH, 1050 Massachusetts Avenue, Cambridge, MA 02138, October 2002, © 2002 by Sendhil Mullainathan and Andrei Shleifer. http://www.nber.org/papers/w9295

For further reading, see this New York Times book review on media bias by Richard Posner.