“More or less” requires explanation in the statement? Not sure what is ment by that? The ice age only requires a 5 degree drop in global climate which is more or less the same as now for example. As for the 70s we could be seeing the oil shortage show up as carbon dioxide influencing the spikes on the graph. Massive use to very little use of oil and I think that was when coal plants started to shut down. Although I could have my timing off on the coal. Or some other function of climate like the transition of change will create greater fluctuations as the weather sorts out temperature leveling.