02263nas a2200157   4500008004100000245010400041210007000145260001200215300001600227490000800243520175000251100001702001700001902018700001802037856005002055       2008                        eng d00aTree rings, δ13C and climate in Picea glauca growing near Churchill, subarctic Manitoba, Canada.  0 aTree rings δ13C and climate in Picea glauca growing near Churchi  c05/2007  a1212–12220 v2523 a<p>How fast and how much climate can change has significant implications for concerns about future climate changes and their potential impacts on society. An abrupt climate change 8200 years ago (8.2&nbsp;ka event) provides a test case to understand possible future climatic variability. Here, methane concentration (taken as an indicator for terrestrial hydrology) and nitrogen isotopes (Greenland temperature) in trapped air in a Greenland ice core (GISP2) are employed to scrutinize the evolution of the 8.2&nbsp;ka event. The synchronous change in methane and nitrogen implies that the 8.2&nbsp;ka event was a synchronous event (within ±4 years) at a hemispheric scale, as indicated by recent climate model results [Legrande, A. N., Schmidt, G. A., Shindell, D. T., Field, C. V., Miller, R. L., Koch, D. M., Faluvegi, G., Hoffmann, G., 2006. Consistent simulations of multiple proxy responses to an abrupt climate change event. Proceedings of the National Academy of Sciences 103, 837–842]. The event began with a large-scale general cooling and drying around ∼8175±30 years BP (Before Present, where Present is 1950 AD). Greenland temperature cooled by 3.3±1.1&nbsp;°C (decadal average) in less than ∼20 years, and atmospheric methane concentration decreased by ∼80±25&nbsp;ppb over ∼40 years, corresponding to a 15±5% emission reduction. Hemispheric scale cooling and drying, inferred from many paleoclimate proxies, likely contributed to this emission reduction. In central Greenland, the coldest period lasted for ∼60 years, interrupted by a milder interval of a few decades, and temperature subsequently warmed in several steps over ∼70 years. The total duration of the 8.2&nbsp;ka event was roughly 150 years.</p>
1 aTardif, J.C.1 aConciatori, F.1 aLeavitt, S.W.  uhttps://greatlakes.ltrr.arizona.edu/node/5226