Each of the last three decades has been successively warmer at
the Earth’s surface than any preceding decade since 1850. The
period from 1983 to 2012 was very likely the warmest 30-year period
of the last 800 years in the Northern Hemisphere, where such assessment
is possible (high confidence) and likely the warmest 30-year
period of the last 1400 years (medium confidence). {WGI 2.4.3, 5.3.5}