The comment that inspired the Revkin headline "Expert on Sunspot Cycles Knocks Cool Forecast"

When I read Nandi's comment, I think he's saying that we can't yet reliably predict the strength of sunspot cycle 25. I don't think Nandi is saying "If sunspot cycle 25 is weak, the planet won't cool".

Revkin.net - Expert on Sunspot Cycles Knocks Cool Forecast

- Readers' Comments - NYTimes.com

This valuable reply came by e-mail from Dibyendu Nandi:
...the underlying physics of the sunspot cycle does not allow for predictions further than one cycle ahead.
...
For the time being, if you want to convince yourself with real data from the Sun and not take my words for granted, look at the Dalton solar minimum, which started around 1800 AD:

http://en.wikipedia.org/wiki/Dalton_Minimum

The sunspot cycle just before the start of the Dalton minimum was very similar in strength with sunspot cycle 23 (the just concluded cycle). The next few cycles were weak, but the Sun was soon back in business with no Maunder minimum like episode.

Cheers,
Dibyendu.

PS: I do not consider myself qualified to speak on the issue of what a weak solar cycle means for the climate

Dalton Minimum - Wikipedia, the free encyclopedia

The Dalton Minimum was a period of low solar activity, named after the English meteorologist John Dalton, lasting from about 1790 to 1830.[1] Like the Maunder Minimum and Spörer Minimum, the Dalton Minimum coincided with a period of lower-than-average global temperatures. The Oberlach Station in Germany, for example, experienced a 2.0°C decline over 20 years.[2] The Year Without a Summer, in 1816, also occurred during the Dalton Minimum.