user: Question: What is the 20 year for Nitrous oxide?
Columns: ['Gas name', 'Chemical formula', 'Lifetime (years)', '20-yr', '100-yr', '500-yr']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Carbon dioxide', 'CO2', 'See above', '1', '1', '1']
SQL:

assistant: SELECT "20-yr" FROM "Table" WHERE "Gas name" = 'Nitrous oxide';