Research by NOAA indicate that the effects of global warming are already irreversible. The IPCC reports attribute many specific natural phenomena to human causes. The expected long range effects of recent climate change may already be observed.

Rising sea levels, glacier retreat, Arctic shrinkage, and altered patterns of agriculture are cited as direct consequences of human activities. Predictions for secondary and regional effects include extreme weather events, an expansion of tropical diseases, changes in the timing of seasonal patterns in ecosystems, and drastic economic impact.