Geoscience Reference
In-Depth Information
intensity of extreme meteorological events; and an increased release of methane
into the atmosphere from permafrost or sub-seabed gas hydrates is unlikely.
• Thecurrentgenerationofgeneralcirculationclimatemodels(GCMs)areunableto
make accurate projections of climate even ten years ahead, let alone the 100-year
periodthathasbeenadoptedbypolicyplanners.Theoutputofsuchmodelsshould
therefore not be used to guide public policy formulation until they have been
validated and shown to have predictive value.
Biological impacts
• Atmospheric CO
2
is not a pollutant. It is a non-toxic, non-irritating, and natural
component of the atmosphere. Long-term CO
2
enrichment studies confirm the
findings ofshorter-term experiments, demonstrating numerous growth-enhancing,
water-conserving, and stress-alleviating effects of elevated atmospheric CO
2
on
plants growing in both terrestrial and aquatic ecosystems.
• The ongoing rise in the air's CO
2
content is causing a great greening of the Earth.
Allacrosstheplanet,thehistoricalincreaseintheatmosphere'sCO
2
concentration
has stimulated vegetative productivity. This observed stimulation, has occurred in
spite of many real and imagined assaults on Earth's vegetation, including fires,
disease, pest outbreaks, deforestation, and climatic change.
• There is little or no risk of increasing food insecurity due to global warming or
rising levels. Farmers and others who depend on rural livelihoods for income are
benefittingfromrisingagriculturalproductivitythroughouttheworld,includingin
partsofAsiaandAfricawheretheneedforincreasedfoodsuppliesismostcritical.
Rising temperatures and atmospheric CO
2
levels play a key role in the realisation
of such benefits.
• Terrestrial ecosystems have thrived throughout the world as a result of warming
temperatures and rising levels of atmospheric CO
2
. Empirical data pertaining to
numerous animal species, including amphibians, birds, butterflies, other insects,
reptiles, and mammals, indicate global warming and its myriad ecological effects
tend to foster the expansion and proliferation of animal habitats, ranges, and
populations, or otherwise have no observable impacts one way or the other.
Multiple lines of evidence indicate animal species are adapting, and in some cases
evolving, to cope with climate change of the modern era.
• Rising temperatures and atmospheric CO
2
levels do not pose a significant threat
to aquatic life. Many aquatic species have shown considerable tolerance to
temperatures and CO
2
values predicted for the next few centuries, and many
