Climate Science

As many will have already heard, our colleague, RC co-founder and friend Michael Mann will receive the Oeschger medal from the European Geosciences Union this week in Vienna. We are delighted to announce this and to congratulate Mike.

Hans Oeschger was a Swiss scientist originally trained as a nuclear physicist. His name is well known in climate science, especially because of his discovery, with Willi Dansgaard, of the Dansgaard-Oeschger events (the rapid climate changes during the last glacial period, first observed in Greenland ice cores). He was even better known in the radiocarbon research community as famously having developed one of the first instruments (the “Oeschger counter”) for measuring carbon-14. This paved the way for determining the age of very small organic materials, including samples from deep-sea sediment cores, which eventually led to the validation of the Milankovitch theory of ice ages. Oeschger and his colleagues in Bern were the first to measure the glacial-interglacial change of atmospheric CO₂ in ice cores, showing that atmospheric concentrations of CO₂ during the glacial period was 50% lower than the pre-industrial concentration, a result predicted by Arrhenius nearly a century earlier. Oeschger may thus be credited with work that was critical to validating two of the most important theories in science: the role of CO₂ in climate change, and the role of changes in the earth’s orbit. Oeschger was also an accomplished musician, and was known to join colleagues in playing chamber music at the International Conference on Radiocarbon.

Oeschger left rather large shoes to fill, and it is a great honor for Mike Mann to win an award bearing Oeschger’s name. Most everyone will probably assume that the award is for Mike’s well known “hockey stick” work. No doubt this is part of it, but the Oeschger award has never been given simply for the publication of one study, but rather for a career’s-worth of outstanding achievements. Most of the previous medalists are a good deal more senior than Mike Mann, and include paleoceanographer Laurent Labeyrie, limnologist Francoise Gasse, ice core pioneers Dominique Raynaud and Sigfus Johnsen and number of other major names in the climate and paleoclimate research, including RC’s own Ray Bradley.

Mike’s work, like that of previous award winners, is diverse, and includes pioneering and highly cited work in time series analysis (an elegant use of Thomson’s multitaper spectral analysis approach to detect spatiotemporal oscillations in the climate record and methods for smoothing temporal data), decadal climate variability (the term “Atlantic Multidecadal Oscillation” or “AMO” was coined by Mike in an interview with Science’s Richard Kerr about a paper he had published with Tom Delworth of GFDL showing evidence in both climate model simulations and observational data for a 50-70 year oscillation in the climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium-7 measurements). Mike’s earliest work, as a physicist, involved studying the behavior of liquids and solids, and trying to understand phenomena such as the structural ordering of high temperature superconductors. In the earth sciences, he has published on topics as varied as the recovery from the KT-boundary mass extinction event and the factors driving long-term changes in the volume of the Great Salt Lake. He has studied and published on the impacts of historical and projected climate change on everything from the behavior of the Asian Summer Monsoon, to Atlantic Hurricanes, to rainfall patterns in the U.S. And for those interested in the hard-nosed statistics by which a scientist’s productivity gets measured, a quick check on the ISI web site will tell you that he has an “H Index” of 40 (that means that 40 of his papers have been cited at least 40 times), more than twenty of his papers have over 100 citations each, and two have over 700. Those are high numbers by any comparison.

But back to the hockey stick. Mike has weathered some rather intense scrutiny and criticism over the years, mostly over the details of a paper nearly 15 years old. Yet the basic conclusions of the “hockey stick” remain, and indeed have been strengthened by subsequent work. Most will be aware, for example, that the conclusion that the past few decades are likely the warmest of the past millennium — i.e. the conclusion of the best-known of Mike’s papers in Nature and Geophysical Research Letters –has never been seriously challenged. But well beyond the simple fact of having been right, Mike’s work was seminal, like Oeschger’s, in playing a pivotal role in launching an entirely new field of study. Although some earlier work along similar lines had been done by other paleoclimate researchers (Ed Cook, Phil Jones, Keith Briffa, Ray Bradley, Malcolm Hughes, and Henry Diaz being just a few examples), before Mike, no one had seriously attempted to use all the available paleoclimate data together, to try to reconstruct the global patterns of climate back in time before the start of direct instrumental observations of climate, or to estimate the underlying statistical uncertainties in reconstructing past temperature changes. Since Mike’s pioneering work (starting in 1995), hundreds of papers have adopted the basic approach he pioneered, and numerous PHD projects have been launched to try to improve upon it. Methods have improved of course, and no doubt will improve further (paleoclimate reconstruction using weather forecast data assimilation methods is the latest and most promising recent development). That Mike is a co-author on many of the latest and most innovative publications in this area — with dozens of different people — attests to the groundbreaking nature of his work.

We look forward to seeing Mike’s award lecture in Vienna, and we offer our heartfelt congratulations to a well-deserved honor. And while we are at it, we should congratulate Mike in advance for his election as a Fellow of the American Geophysical Union; that honor will be bestowed this fall in San Francisco.

Finally, we would be remiss to not mention that Mike has spent much of the past few months touring and lecturing on his experiences as an accidental and reluctant public figure in the debate over human-caused climate change, as detailed in his recent book The Hockey Stick and the Climate Wars: Dispatches from the Front Lines.