That is possible because there are no ice core records back that far. But they happen in a regular cycle about every 124k. And they have figured that they were once even more often and closer together than they have been the last 350k. And each warm period only pasts about 24k out of each 124k cycle. So by the records they do have back 350K it was cold about 80% of the time span.
Haven’t talked to you in awhile, good to see you are well. :)
https://www.ncdc.noaa.gov/abrupt-climate-change/Glacial-Interglacial%20Cycles
Yes, still alive and kicking. Ice cores is not the only way to measure this. Sediment cores and stelactites (sp?) are others. There seems to have been a destinct change in the cycles around 1.5 million years ago.