I've been involved for a long time going over astronomical influences on climate. My job is to be an astronomer and I don't know about climate. Maybe you think this is impossible, but I think it would be too complex to say whether a record of some sort within the ice was the driving force of all climate there is, or just a record of yet another thing coming from the sky. In any case the big deal in this area is calculating common Insolation curves presented in the following way: 1. without atmospheric extinction Insolation=Solar constant * sin(altitude of sun above horizon) at one geographic spot, at one moment during the day 2. with extinction k=0.8 Inso=So * sin(a) * k^(1/sin(a)) In the short term (eg. 100 years) the math behind general spherical astronomy is easy. The case 1 is integrable, the case 2 is only for numeric computation. We calculate altitude of sun every day, any time. In the very very long term the orbit of Earth is changing shape, and axis of Earth is precessing. Hence, there is some more complex general formula for this case which will tell us the altitude of the sun depending from geographical latitude, obliquity, eccentricity, ecliptic longitude of the sun... Although I demonstrate all this to some point within my powers as a student and a jerk, I live in a system that hates quoting and demands evidence. Given this compilation of data: http://www.ncdc.noaa.gov/paleo/pubs/huybers2006b/ we can look into a couple of graphs: http://www.people.fas.harvard.edu/~phuybers/Inso/Summer_energy_15N.pdf http://www.people.fas.harvard.edu/~phuybers/Inso/Summer_energy_65N.pdf Notice one odd thing: In the middle of summer these two very distant geographical latitudes, have the same local maximum of Insolation - a whole 500 W/m^2. Would someone care to comment on this? you won't be quoted I promise!