Maximum Northern Hemisphere warming rates before and after 1880 during the Common Era

Abstract We find that maximal decadal Northern Hemisphere warming increases as rapidly before after the industrial revolution (0.86 °C decade −1 1880 and 0.60–0.68 1880). However, whereas number of periods with large increase decrease rates were about equal (267 vs. 273), there are more high (35) than (9). The same patterns hold for bi-decadal rates. time windows greater 20 years, slope in global becomes 1880. After 1971, is only one short 11 year period negative slopes. This reflects higher frequency positive slopes during caused by contribution greenhouse gases (GHG). Maximum temperature changes detrended series associated beginning end extreme warm or cold sub periods. They occurred throughout all Common Era. Because showed sign a pacemaker mechanism (regular cycle periods) we suggest ocean variabilities dominating multidecadal variability