Climate Reversal [Science, September 4, 2009]

CREDIT: KAUFMAN ET AL. The climate and environment of the Arctic have changed drastically over the short course of modern observation. Kaufman et al. (p. _1236_ (http://www.info-aaas.org/l.jsp?d=2403.285504.654.2bqZKHifm) ) synthesized 2000 years of proxy data from lakes above 60° N latitude with complementary ice core and tree ring records, to create a paleoclimate reconstruction for the Arctic with a 10-year resolution. A gradual cooling trend at the start of the record had reversed by the beginning of the 20th century, when temperatures began to increase rapidly. The long-term cooling of the Arctic is consistent with a reduction in summer solar insolation caused by changes in Earth's orbit, while the rapid and large warming of the past century is consistent with the human-caused warming.