| 英文摘要: | The recent slowdown (or 'pause') in global surface temperature rise is a hot topic for climate scientists and the wider public. We discuss how climate scientists have tried to communicate the pause and suggest that 'many-to-many' communication offers a key opportunity to directly engage with the public. Since the late 1990s, global mean surface temperature increased more slowly than during the preceding two decades. The reasons for this 'pause' are being actively debated by the climate science community1, 2, 3, 4. The recent Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) concluded in their Summary for Policymakers (SPM) that this slowdown “is due in roughly equal measure to a reduced trend in radiative forcing and a cooling contribution from natural internal variability”1. Discussion of the pause, while a relatively small part of the IPCC report, was prominent in the mainstream media reporting5 following the release of the AR5 Working Group I SPM. Much of the coverage accurately reflected the views of scientists, although some was less aligned with the conclusions of the IPCC. This media attention was perhaps predictable, given the long-term sceptical narrative about the pause, which can be traced back to at least 20066. For example, in 2007, New Statesman proclaimed that “global warming has stopped”7, starting a pervasive trend in some parts of the media (especially in the UK) to prominently highlight the slowdown and suggest that climate models are “running too hot”8 or that climate sensitivity is on “negative watch”9. These media articles raise questions about the public communication efforts of the climate science community, especially since the 'Climategate' affair of 2009, and highlight the need for climate scientists to accurately convey information of societal relevance to a very wide range of interested parties10, 11. Did the climate science community do enough in communicating the slowdown, and how could it do better in the future?
The IPCC suggests that the slowdown is likely to be due to a combination of factors1. Here we mainly focus on the communication of one particular aspect — the role of internal climate variability — but the radiative forcing changes are also important. The peer-reviewed literature contains much discussion of unforced decadal fluctuations in global surface temperature and the IPCC discusses internal climate variability extensively in all of their reports. Such variability has been invoked to help explain both the early twentieth-century warming12 and the faster warming during the 1980s and 1990s13. In addition, projections from global climate models have shown decadal periods of cooling embedded within longer-term warming from when they were first developed14 to the present15, 16. However, to our knowledge, the possibility that warming might slow due to internal variability was not highlighted by the mainstream media prior to 2006, raising the possibility that climate scientists did not stress the importance of such variability enough. For example, during an otherwise successful UK press briefing on the pause in 201317, one senior science journalist remarked that he had “never heard leading researchers mention the possibility [of a slowdown] before”18. What could have caused a breakdown in communication of this magnitude? First, it is possible that the chance of a slowdown was communicated effectively to the media, and subsequently ignored as not newsworthy. Alternatively, previous communications may have focused on long-term changes to inform mitigation discussions, whereas there is now more focus on near-term adaptation issues, for which climate variability is more important. Although several papers have estimated the probability of a pause19, 20, 21, they were published after it had started. Also note that the IPCC has not included a clear statement of the chance of a slowdown in any of its SPMs (Box 1).
Box 1: IPCC summary statements on the role of climate variability.
AR1 SPM 1990 — “the Earth's climate would still vary without being perturbed by any external influences. This natural variability could add to, or subtract from, any human-made warming; on a century timescale this would be less than changes expected from greenhouse gas increases.” AR2 SPM 1995 — “Any human-induced effect on climate will be superimposed on the background 'noise' of natural climate variability.” AR3 SPM 2001 — “Changes in climate occur as a result of both internal variability within the climate system and external factors.” AR4 SPM 2007 — “On [regional] scales, natural climate variability is relatively larger, making it harder to distinguish changes expected due to external forcings.” AR5 SPM 2013 — “In addition to robust multi-decadal warming, global mean surface temperature exhibits substantial decadal and interannual variability. 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.”
Trends in online searches suggest that media articles, even if published in a single country, can drive interest and discussion among the global public. Google trends (Fig. 2) suggest that searches for 'global warming stopped' increased sharply in early 2008, just after the New Statesman article7. A peak in October 2012 can potentially be traced to an article in Mail Online29. From March 2013, the term 'global warming pause' became popular, coincident with the phrase's use in articles in Mail Online8 and The Economist9. Another peak in September 2013 is coincident with media coverage of the launch of the IPCC AR5 Working Group I SPM1.
| http://www.nature.com/nclimate/journal/v4/n3/full/nclimate2150.html
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