evidence: "This reconstruction suggests that current temperatures are unprecedented in 24,000 years, and also suggests that the speed of human-caused global warming is faster than anything we've seen in that same time," said Jessica Tierney, a UArizona geosciences associate professor and co-author of the study. [...] Computer-simulated climate models, on the other hand, provide temperature information based on scientists' best understanding of the physics of the climate system, which also isn't perfect.