and Northern Hemisphere sea ice extent, thinner sea
ice, shorter freezing seasons of
lake and river ice, glacier melt, de-
creases in permafrost extent, increases in soil temperatures and
borehole temperature profiles, and sea level rise, provide additional
evidence that the world is warming. {WGI 3.9}
Of the more than 29,000 observational data series, from 75 stud-
ies, that show significant change
/media/loftslag/IPPC-2007-ar4_syr.pdf