Winter is Coming

What It Covers

How the 1980 discovery that an asteroid killed the dinosaurs led physicist Luis Alvarez and his son Walter to develop nuclear winter theory, potentially preventing nuclear war between the US and Soviet Union.

Key Questions Answered

• •Iridium detection method: Luis Alvarez measured rare element iridium in rock layers to date geological formations, discovering 30 times expected levels at the KT boundary, proving a massive asteroid impact 66 million years ago wiped out dinosaurs.
• •Nuclear winter modeling: Brian Toon and Richard Turco calculated that 70,000 nuclear weapons would inject enough dust and smoke into the atmosphere to cause sub-freezing temperatures globally for months, potentially causing human extinction through prolonged darkness and agricultural collapse.
• •Public communication strategy: Carl Sagan bypassed traditional scientific channels by publishing nuclear winter findings in Parade Magazine, reaching tens of millions of Americans simultaneously with scientific elite, making existential threat accessible to general public rather than just policymakers and academics.
• •Diplomatic impact on disarmament: After Carl Sagan briefed Soviet Central Committee on nuclear winter in 1986, Gorbachev reportedly told advisors the arms race was over, with both Reagan and Gorbachev later crediting nuclear winter theory as reason for controlling nuclear weapons.