Time has proven that even 22 years ago climate scientists understood the dynamics behind global warming well enough to accurately predict warming, says an analysis that compares predictions in 1990 with 20 years of temperature records. …
… 22 years ago, scientists understood one crucial factor:
“The prediction basically depended on how much carbon dioxide was already in the atmosphere, and that has been what’s important,” Stone said. [http://www.livescience.com/19466-climate-change-myths-busted.html">The Reality of Climate Change: 10 Myths Busted]
What matters is the accumulation of carbon dioxide in the atmosphere since the Industrial Revolution; short-term changes in emissions have relatively little effect on overall warming, Frame and Stone write.