A sudden spike in global warmth is so extreme, it’s mysterious

Record warmth is to be expected as greenhouse gases heat up the planet. But a spike in global temperatures observed in September was so much more dramatic than past extremes that some climate scientists said it defies a simple explanation.

A National Oceanic and Atmospheric Administration analysis released Friday further cemented what several other data sets had already affirmed: September was not just the globe’s warmest on record, but its most atypically warm month in nearly two centuries of observations. It was 0.83 degrees above the old record for the month, a staggering departure from what was already extreme.