claim: While an isolated heatwave can be put down as an anomaly, the scale of this phenomenon points to global warming as the culprit, scientists said.
evidence: Historically, the clarity of Lake Tahoe continued to decrease through 2010, when the average Secchi depth, 64.4 feet (19.6 m), was the second lowest ever recorded (the lowest was 64.1 feet (19.5 m) in 1997).