2011-03-24 11:40:30New paper: Maunder Minimum sun not as cool as previously thought
John Cook


New paper that has another take on past solar activity (would be interested in Sami Solanki's take on this):

The minimal solar activity in 2008–2009 and its implications for long-term climate modeling

Variations in the total solar irradiance (TSI) associated with solar activity have been argued to influence the Earth's climate system, in particular when solar activity deviates from the average for a substantial period. One such example is the 17th Century Maunder Minimum during which sunspot numbers were extremely low, as Earth experienced the Little Ice Age. Estimation of the TSI during that period has relied on extrapolations of correlations with sunspot numbers or even more indirectly with modulations of galactic cosmic rays. We argue that there is a minimum state of solar magnetic activity associated with a population of relatively small magnetic bipoles which persists even when sunspots are absent, and that consequently estimates of TSI for the Little Ice Age that are based on scalings with sunspot numbers are generally too low. The minimal solar activity, which measurements show to be frequently observable between active-region decay products regardless of the phase of the sunspot cycle, was approached globally after an unusually long lull in sunspot activity in 2008–2009. Therefore, the best estimate of magnetic activity, and presumably TSI, for the least-active Maunder Minimum phases appears to be provided by direct measurement in 2008–2009. The implied marginally significant decrease in TSI during the least active phases of the Maunder Minimum by 140 to 360 ppm relative to 1996 suggests that drivers other than TSI dominate Earth's long-term climate change.

Green Grok's take:

Solar Doubt Doth Grow

The authors conclude: “If the 2008–2009 solar ... activity is indeed similar to the Maunder Minimum level ... then it would appear that drivers other than TSI [i.e., the Sun] dominate Earth’s long-term climate change.”

Interesting, but I don’t think I would go quite that far. Just because the Sun may not have played a major role in the Maunder Minimum does not necessarily mean that the Sun is not a driver in all long-term climate change.

What I take away from Schrijver et al’s work is that the climatic forcing (whether it came from the Sun or something else) that led to the Little Ice Age may have been much smaller than we thought. And what that means is that the climate sensitivity — the amount of temperature change for a given climate forcing — is also larger than what's included in current climate models. And that would mean that the eventual climate response to the rise in carbon dioxide and other greenhouse gases will be larger than now estimated. It’s all a fascinating puzzle that, given the current trajectory of things, we seem hell-bent on doing the experiment so that we can make sure all the puzzle pieces fit.

Not sure I agree with that interpretation - climate sensitivity may be higher but there might be other forcings (eg - high volcanic activity) which drove LIA cooling. Anyway, interesting stuff.

2011-03-24 12:27:40Sensitivity
Dana Nuccitelli
Was going to say the same thing - it certainly isn't indicative of low sensitivity at least.
2011-03-24 14:14:38
Glenn Tamblyn


The other take from this is it might give more support to the idea that there is a greater impact from solar cycle variability than previously thought.

Perhaps something with a cumulative effect so there is a time lag associated with the effect so that longer quiet periods have a greater impact than short ones. That might explain why it doesn't seem as apparent from the normal solar cycle but showed up in the last cycle.

I'm not so much suggesting Svensmark's GCR/Clouds idea but possibly other effects from Solar variability - UV levels and Ozone for example.

But really just speculation.

2011-03-24 18:19:45
Rob Painting

Full paper here. I take it the "skeptics" are getting their panties in a twist over this?.