The humble hagfish is an ugly, gray, eel-like creature best known for its ability to unleash a cloud of sticky slime onto unsuspecting predators, clogging the gills and suffocating said predators.

For hundreds of millions of years, Earth’s climate has warmed and cooled with natural fluctuations in the level of carbon dioxide (CO₂) in the atmosphere. Over the past century, humans have pushed CO₂ ...