That is indeed an assumption on my part, although there is evidence of such regulation that I, at least, find compelling; for example: http://en.wikipedia.org/

That is indeed an assumption on my part, although there is evidence of such regulation that I, at least, find compelling; for example: http://en.wikipedia.org/wiki/File:Vostok_420ky_4curves_insolation.jpg http://en.wikipedia.org/wiki/File:Vostok_420ky_4curves_insol... and it's worth pointing out that long term regulation and the shorter term variations that you mentioned aren't necessarily incompatible. IANA Climate Scientist though!