Climatologists look for climate change in many components of the climate system. Which of the following statements has the least direct evidence? A. Global mean surface temperature has increased since 1850.
B. Arctic sea ice, glaciers, and ice sheets have decreased in size over the past 50 years.
C. The length of the growing season in the US has decreased since the 1890s.
D. Global mean sea level has risen significantly since 1880.