125,000 years ago the CO2 was at nearly 300 ppm, the CH4 was at 0.8 ppm, and there were no industrial GHGs for which there are no natural analogs.
Today, we are at 390ppm on CO2, 1.8 ppm on Ch4, and have numerous industrial GHGs which are hundreds to thousands of times as effective GHGs as CO2. And there is a lag of 30 to 50 years between the level of GHGs and the time the full effects are felt.
So, we are far above the GHG levels of the period quoted. And the information confirms rather than contradicts present climate theory. With far less GHGs, there were strong effects we have yet to see from the amount we have at present. You might well have thrown in that the sea level was at least 3 meters above the present.
Also, there is the rest of the article;
Fossil DNA Proves Greenland Once Had Lush Forests; Ice Sheet Is Surprisingly Stable
This theory however, was not confirmed by Willerslev and co-workers subsequent datings. He analysed the insects' mitochondria, which are special genomes that change with time and like a clock can be used to date the DNA. He also analysed their amino acids which also change over time. Both datings showed that the insects were at least 450,000 years old.