A review of the scientifi c literature concerning
the environmental consequences of increased levels of atmospheric
carbon dioxide, the most prominent greenhouse gas contributed by
human activities, leads to the conclusion that increases during
the twentieth century have produced no deleterious effects upon
global climate or temperature. Increased carbon dioxide has,
however, markedly increased the growth
rates of plants as inferred from numerous laboratory and field
experiments. There is no clear evidence, nor unique attribution,
of the global effects of anthropogenic CO2 on climate.
Meaningful assessments of the environmental impacts of
anthropogenic CO2 are not yet possible because model estimates of
global and regional changes in climate on interannual, decadal
and centennial time-scales remain highly uncertain.