' is it really a surprise that we're heading towards another one (which is due anyway).'
No it bloody isn't!
Can you please find a geological textbook that says the next glacial maximum is due? The best claim you can make is that in the early 1970s a *minority* of scientists studying the climate proposed that the Earth was likely to head into a period of general cooling which might end up as an ice age (we'll skip the technicality that we're actually still in an ice age).
The work began with Stephen Schneider at NASA Goddard Flight Center and got into the New York Times. Around the same time, a report by the National Academy of Sciences also suggested a 'finite possibility' that the Earth's climate would begin cooling within the next century. The stories got traction for a number of reasons:
Research had been going on into Milankovich Cycles - regular changes in the tilt of the Earth's axis on a geological timescale which appear to be *partially* related to glaciations. Running the Cycles forward showed that the Earth was heading towards a part of the cycle which would produce greater amounts of cooling.
The then state of knowledge of glaciations was very poor - we had not done any deep drilling of ice cores. There was a general assumption that the warmer interglacials, such as the current Holocene, lasted no more than 10,000 years; and that the previous interglacial had lasted less than 5,000 years. The Holocene interglacial had been going for about 10,000 years, so it was reasonable to assume the ice sheets were most likely to begin expanding again in the geological near future.
There had been a very mild cooling from the 1940s onward which was believed to have been driven by rapid industrialisation producing smoke, soot and dust and by the cultivation of previously virgin land producing even more dust.
Schneider performed a simulation contrasting the cooling effect of these aerosols against the known warming effect of increased CO2 from fossil fuels. He made a prediction of the future climate if the known trends continued into the future. His 1971 paper suggested the cooling effect was dominant and would tip the Earth towards another glacial.
Schneider quickly realised his numbers for future cooling were not realistic (he had used local concentrations of pollutants on a global scale - there were too many of them), when he dialled the aerosols back to more realistic values in his second simulation, it was clear that the warming effect was dominant.
Since then we've learned a lot. Milankovich Cycles are a good, but not total explanation of glaciations. We now know interglacials last up to about 100,000 years and we're pretty sure (again from the ice evidence) that much of the cooling in the middle part of the 20th Century was caused by an upspike in volcanic activity.
Schneider's paper came in a poorly established field without a large amount of supporting work. It was a good piece of work and he deserves credit for re-running his work with better figures. But he was not the only person researching future climates. Between 1965 and 1979, 44 scientific papers were published that predicted a warming world - and some were pointing to CO2 as the driving force, 20 thought there would be no overall change; just 7 predicted cooling.
There's a review of those papers here:
Can we now bury that myth alongside the person who suggested I should take up drinking instant coffee?