Pouring through four decades of satellite data, climate scientists have concluded for the first time that humans are pushing seasonal temperatures out of balance-shifting what one researcher called the very “march of the seasons themselves.” Ever-mindful of calculable uncertainty and climate deniers, the authors give “odds of roughly 5 in 1 million” of these changes occurring naturally, without human influence. Like homicide detectives, climate scientists are continually sifting through evidence looking for what they also call “fingerprints.” Over the years, they’ve teased out the human signal from Earthly noise in annual and decade-spanning temperature records, marine chemistry, rapid Arctic change and more. What they discovered is an uneven pace of seasonal change in the atmosphere above the Northern and Southern Hemispheres’ temperate zones.