Pollution (and Global Warming?) as a Historical Tool

Hmm. I see that "Metal Pollution From Medieval Mining Persists" (via Cronaca), and that a "summer heat wave has unearthed a historic past" (via Mirablilis). Then I learned from Brian Ward-Perkins in his Fall of Rome) that archaelogists have used the polution caused by Roman metalsmithing--as found buried in the Arctic ice cap--to gauge the extent of industry prior to Rome's fall. All in all, I'd say some good can come from global warming and pollution!