The Arctic's current warming trend is the worst it's experienced in at least 44,000 years—and possibly even longer—a new study has concluded. Scientists examining vegetation in the Canadian Arctic found recently-exposed moss that, based on radiocarbon dating, was between 44,000 and 51,000 years old—meaning the ice surrounding it hadn't melted in at least that long, Scientific American reports. "Our study pushes the clock way back," says one researcher at the University of Colorado.
What's more, because radiocarbon dating is only accurate to about 50,000 years, and geological records show a glacial period preceding that, it's probable that current temperatures actually haven't been seen in 120,000 years, the lead researcher tells Phys.org. That the ice is melting now, but failed to melt during the extremely warm Holocene Thermal Maximum, is a sign that this isn't natural variance, and is almost surely caused by greenhouse gases, he adds. "Nothing else out there can explain it." (Read more global warming stories.)