evidence: The effect of the orbital features on the total sunlight reaching the Earth is almost zero; the sunshine is just moved between areas and seasons. But, the whole world cools into an ice age, and the whole world warms coming out of an ice age, despite half the world getting less sun when the other half gets more. And, so far, all the explanations of this require the effects of the CO2, which beautifully explain it. A recent study by Dr Daniel Baggenstos at the University of Bern and colleagues examined the relative contribution of different factors during the transition from the last ice age to the current interglacial period. They found that albedo – changing reflectivity of the surface as ice sheets shrink – was the largest factor responsible for about half of the warming, while changing CO2 concentrations and other greenhouse gases was responsible for 37%, while reductions of the amount of reflective dust and other aerosols in the atmosphere made up the remaining 13%. [...] However, if CO2 only contributed around 35% of the warming at the end of the last ice age – with changing albedo from melting ice sheets playing a major role – this would imply a climate sensitivity of around 3C – much more in-line with current model estimates, though with a very large uncertainty given the limits to how accurately models simulate global changes over that period.