Did they take into account volcano eruptions and Maunder Minimums? Those have a way of drastically cooling things down.
-Blast
The current models do take natural factors into account.
Volcanism and sun spot cycles have resulted in short term reversals in the past ("Little Ice Age"), but have not altered longer term trends.
Exactly.
Phil Plait's blog has a fascinating graph showing models of natural effects only, natural effects combined with human effects, and the
actual observed data. The graph is from the
National Climate Assessment, which focuses on effects on the US.
Natural variations in climate include the effects of cycles such as El Niņo, La Niņa and other ocean cycles; the 11-year sunspot cycle and other changes in energy from the sun; and the effects of volcanic eruptions. Globally, natural variations can be as large as human-induced climate change over timescales of up to a few decades. However, changes in climate at the global scale observed over the past 50 years are far larger than can be accounted for by natural variability.
Especially interesting is the
section on how changes are effecting local regions.
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