Since the publication of the hacked emails from the University of East Anglia's Climate Research Unit (CRU) last November, we've been inundated with news reports and opinion pieces questioning the scientific consensus behind climate change. An editorial in today's Wall St. Journal on "The Continuing Climate Meltdown" is just the latest example of this trend, following a weekend that saw the release of a remarkable BBC interview with the CRU's former director. The fact that all this coincides with a northern hemisphere winter that has deposited record snowfalls on regions that don't normally see much of the white stuff serves to reinforce the message that something is amiss with global warming theory. It has also had me wondering if I moved far enough south, as I cope with "ice dams", cabin fever, and other consequences of a pair of back-to-back blizzards in the D.C. area. While I agree that the recent revelations have given rise to an understandable wave of doubts regarding climate change, this may say more about the way that extreme climate predictions have been played up in the last several years than it does about actual climate change.
Even the most ardent adherents of the view that climate change is real, man-made to a significant extent, and extremely challenging for humanity must agree that the science supporting this perspective has had a rough couple of months--largely deserved. Whatever the "Climategate" emails said about the underlying analytical rigor of the dominant scientific interpretation of global warming, they revealed a worrying degree of defensive groupthink and gatekeeping among leading climate researchers. I'm pleased to see that an independent group has been set up to examine the practices at East Anglia-CRU, though the inquiry has already experienced controversies of its own.
Meanwhile the Intergovernmental Panel on Climate Change (IPCC), of Nobel Peace Prize fame, is under fire for incorporating unwarranted claims in its reports, including a shockingly sloppy assertion about the rate at which glaciers are disappearing. This has exposed a process that in some instances gave magazine articles and unpublished papers the same credence as peer-reviewed scientific papers in recognized journals. For all the vitriol I see directed against "climate skeptics", the climate change community should accept that these are mainly self-inflicted wounds, and that much of the current public doubt about climate change stems from the unraveling of exaggerated predictions that were expounded without a clear, accompanying explanation of the associated caveats and uncertainties, possibly to promote quicker action by governments.
In contrast, the BBC's interview with Dr. Jones is full of nuances and caveats--though hardly outright retractions, as some have characterized his remarks. I was particularly interested in his comments on the Medieval Warm Period. Although he appears not to have "told the BBC that the world may well have been warmer during medieval times than it is now," he did seem to suggest that we simply don't have sufficient data to determine whether the warming that led to the settlement of Greenland by the Vikings and the cultivation of wine grapes in England was confined to the northern hemisphere or global in extent. Instead of prompting an assumption it wasn't global, this gap in our knowledge ought to galvanize the urgent gathering and correlation of paleoclimate data--samples of the kinds of proxies used to assess temperatures before instruments to measure them (or people to read the instruments) existed. That's because this isn't a quibble over some esoteric bit of history, but a crucial gauge of just how unprecedented the warming of the past several decades has been.
Then there's the temperature data itself. Although Dr. Jones concurred that global warming since 1995 has just missed being statistically significant, the data from the CRU and similar data from NASA do show that on average the last decade was warmer than the 1990s, which were in turn warmer than the 1980s. Despite all the talk of global cooling, the last two years still easily make the top 10 list for warmest years of the last century, and global temperatures currently average about 0.8 °F warmer than in the 1970s. But that doesn't mean that there aren't problems here, as well. Dr. Jones referred the BBC to a map of the weather stations providing the global temperature data compiled by the UK's Met Office (the national weather service) and processed by the CRU. It reveals such measurements to be very dense in the developed countries of the temperate zones and quite thin on the ground--or sea--in the tropics and the high latitudes that account for much of the earth's surface. And even the historical temperature data for the US are still subject to significant revisions, as I noticed yesterday when I rechecked the comparison between 1998 and 1934 than I wrote about several years ago.
So where does this leave us? From my perspective it requires us to think about the definition of a successful scientific theory as one that provides the best explanation for the evidence we see--even if that evidence is incomplete, as seems to be the case here. The fact that some scientists seem to have behaved badly or that others--mostly non-scientists--have promoted alarming-but-uncertain predictions as proven and now have egg on their faces doesn't alter the fact that "anthropogenic global warming" (AGW) based on greenhouse gas emissions still seems to explain more of what we observe going on than any other theory at this point. Hypotheses such as the one attributing warming to the influence of cosmic rays on cloud formation must go through a great deal more vetting before supplanting AGW.
While considerable progress has been made in the last decade solidifying the evidence supporting the AGW theory, significant uncertainty still remains about the future consequences it suggests, particularly as relates to regional impacts and changes in precipitation. A lot more also needs to be done to clarify the relationship between proxy data and instrumental temperature data, and to ensure that the latter are consistent and truly representative. However, I don't see these deficiencies as justifying complete policy paralysis, particularly when it comes to those actions that can be accomplished relatively cheaply, such as improved energy efficiency, or that offer substantial benefits for other concerns such as energy security, including expanding nuclear power, low-cost renewable energy, and R&D to bring down the cost of other renewables. As for whether the time is right to pursue more comprehensive measures, there's a legitimate debate to be had, but it shouldn't start from the false assumption that anthropogenic global warming has been disproved.