A new study shows that over the past 20 years, vegetation in the 40-70 north latitude zone has in general been increasing.
The vegetal enhancement, as measured from NOAA polar-orbiting satellites, seems to be correlated with temperature increases as measured on the ground at thousands of stations.
This region of the Earth has warmed about 0.8 degrees C since the early 1970s. The greening is not uniform around the world, but occurs more in a band across Eurasia and much less in North America.
Scientists at the University of Boston and the Goddard Space Flight Center report that the northern Eurasian growing season increased to be an average of 18 days longer (spring arriving a week earlier, fall arriving 10 days late) over the period 1981-1999, while the northern Western Hemisphere season became about 12 days longer.
(Reference: Zhou et al., Journal of Geophysical Research (Atmospheres), 16 Sept 2001; available online at this URL.)
(Editor's Note: This story is based on PHYSICS NEWS UPDATE, the American Institute of Physics Bulletin of Physics News Number 557, September 20, 2001, by Phillip F. Schewe, Ben Stein, and James Riordon.)