On Monday, journalists preparing to cover Pope Francis’s intensely anticipated encyclical on the environment were stunned to learn that a version of the document had been leaked online three days early. A mad dash ensued to translate the Italian language text, whereupon sure enough, we learned that Francis’s words mostly surprised no one — they included repeated invocations of how environmental degradation imperils the poor and disadvantaged, and a robust statement that climate change is mostly caused by humans, the scientific consensus view.

“The Pope may not be a climate scientist but, unlike many of the prominent climate change-denying Republican politicians in the U.S., he knew to consult with the best scientists to make sure he got the science right—and he did,” Michael Mann, a prominent climate researcher at Penn State University, said by e-mail.

We’re used to leaks in the rough and tumble of politics — but with a major papal document? That seemed somehow shocking.

“To have it leaked and become part of the political circus that is our politics today, it’s not consistent with the gravity of an encyclical letter,” said Andrew Hoffman, professor of sustainable enterprise at the University of Michigan. “That’s unfortunate. But I  think it also speaks to the importance that the Pope is bringing to his office….I think back on other encyclical letters that have been released by the Vatican and I can’t imagine any that would have generated this much attention had they been leaked.”

But if leaks are not something we expect with papal encyclicals, they are indeed something that has shaped the highly charged climate change debate.

For instance, in 2013, a draft version of the United Nations’ Intergovernmental Panel on Climate Change’s “Summary for Policymakers” was leaked and widely reported on and discussed. And that shaped the debate significantly.

In particular, as I reported back then, the leaked document contained a different treatment of the so-called global warming “pause” or “hiatus” than did the final document. It stated that the rate of warming was lower between 1998 and 2012 than over a much longer time period, but lacked several caveats for interpreting this statement that the final document contained. The final document, in contrast, warned that 1998 was a strong El Nino year – thus starting the time series at a sharp high point — and added that, “Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends.”

Thus, the leak of the 2013 Summary for Policymakers had the effect of feeding into the global warming “pause” narrative — which soon became the number one means of challenging the validity of the climate concerns that the new report articulated.

Unlike the Vatican leak, at least climate science leaks aren’t all that surprising. There are plenty of potentials for leaks in the IPCC process, said climate researcher Kevin Trenberth of the National Center for Atmospheric Research. “Clearly with IPCC there are hundreds of scientists involved and many ways leaks can occur either deliberately of even unintentionally as scientists share with colleagues when they are not supposed to,” Trenberth said by e-mail.  “It is an honor-based system.”

“It is a sign of utmost disrespect to leak a draft of the encyclical against Pope Francis’s wishes,” adds Penn State’s Michael Mann. “While this sort of thing is par for the course w/ e.g. the reports of the IPCC, this sort of disrespect is unprecedented, to my knowledge, in the history of the Papacy.”

A different kind of climate-related leak probably had even more severe consequences. In 2009’s so-called “ClimateGate” scandal, a computer hacking led to the revealing of a large trove of e-mails from climate scientists. The e-mails’ contents were subsequently pored over and sometimes taken out of context, creating in some cases the appearance that researchers had been engaged in twisting data to make climate change appear worse than it actually is.

For instance, a sentence in one e-mail, referring a scientific “trick” of “adding in the real temps to each series for the last 20 years (ie from 1981 onwards) amd [sic] from 1961 for Keith’s to hide the decline,” was often misunderstood. “Trick” simply referred to a skilled scientific technique, and the “decline” in question was not about global temperatures, but about an odd trend in tree ring data.

But more careful parsing of what the e-mails actually meant tended to relieve concern. As a UK parliamentary inquiry put it regarding the quotation above (and this is just one example from the e-mails), “We are content that the phrases such as ‘trick’ or ‘hiding the decline’ were colloquial terms used in private e-mails and the balance of evidence is that they were not part of a systematic attempt to mislead.”

Thus, in the past, leaks haven’t been very good news for climate science — especially in the short run. They knock the research community off balance and give critics an opening. In the much longer term, though, it’s less clear that they have had a truly momentous impact. The world is still just as worried about and focused on climate change as it would be without these leaks.

In the case of Pope Francis, it is unclear what effect the leak will have — it will probably take a few days to see if critics use the apparently non-final document to try to undermine the Pope in some way.

But the impact is likely to be modest. The encyclical in its final form will remain a major church document and its influence is unlikely to be much diminished by the existence of a copy that may deviate from it in a few respects.

Nonetheless, the Pope’s message and presentation have definitely been thrown off — and the organization of the overall encyclical narrative, from the Vatican, may now be much more difficult.

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