Understanding Climate Cycles

Despite all the hysteria about alleged CO2 induced climate change, natural cycles will almost certainly predominate.  Human civilization has evolved during one of our relatively short interglacial cycles, a period which will inevitably end and for which we should be preparing.   The primary driver of long-term climate change is variation in the amount and intensity of solar radiation reaching earth.  Earth is tilted with respect to its orbital plane around the sun.  The angle of tilt changes, the axis of rotation moves.  The earth’s orbit is not perfectly round and changes.  All these factors change the solar energy reaching our atmosphere, particularly in the northern hemisphere.  Each varies on a different time frame, so sometimes they are opposing in effect, sometimes they are additive.

In this study the authors use an analysis of all glaciation cycles in about the last million years to try to tease out the relative effects of each factor.  They find that ice age starts are likely correlated most strongly with the tilt of the Earth’s rotational axis and the initiation of the interglacial periods (which are shorter) with both rising obliquity (tilt) and precession.  This leads them to create an algorithm incorporating various factors.

According to these authors, their algorithm predicts that the next glacial age will begin in about 7000 years.  Of course they constantly caveat their predictions by referring to disruption by CO2 levels.  Hard to get published in Science if you don’t do that.  But they know very well that CO2 levels vary in a different way and aren’t clearly linked to either the start of end of an ice age, but may lag those changes.   (Science Article)