from 1998) to 2008 (Fig. 16.2; Lyman et al. 2010). Other strong temperature
oscillations have occurred in historical times, including the warm medieval optimum
and the “little ice age” from 1600–1860, a cold phase in which continental glaciers re-
expanded and growing seasons were short. Our current concern with warming comes
because it is happening in an era when record-keeping and science are advanced
enough to see the process and offer explanations, because its effects will in some
ways be unpleasant, and finally because we seem to be causing it. A significant aspect
of warming is that it has been greater at high than at low latitudes (temperature
anomaly geography by decades from 1880 to 2009 is shown in sequence at:
http://earthobservatory.nasa.gov/Features/WorldOfChange/decadaltemp.php?src=eoa-
features.
Fig. 16.1 Global average temperatures, 1880–2010. US National Oceanic and
Atmospheric Administration (2010). Go to
http://www.ncdc.noaa.gov/img/climate/research/2009/global-jan-dec-error-bar.gif.
Fig. 16.2 Thirteen estimates with their mean (dark line with std. error bars) of global
ocean heat increase plotted as anomalies from 1993 to 2008. The gain was about 13 ×
1023 Joules.
(^) (After Lyman et al. 2010.)