Two decades ago, Hurricane Katrina spun up like a massive atmospheric engine, using warm ocean water as fuel. Making landfall as a Category 3 storm with maximum sustained winds of 125 mph, it devastated New Orleans — surging seawater over levees, killing nearly 2,000 people, and causing more than $150 billion in damage. Even though engineers have since significantly bolstered those levees, their ability to withstand climate-supercharged cyclones remains uncertain .

In the past 20 years, researchers have gotten ever better at determining how much human-caused climate change has contributed to extreme weather — a field called attribution science — thanks to more data and better modeling. On the 20th anniversary of Katrina, a new report from the research group Climate Central looks back

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