Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_21350772_2 (gas_name VARCHAR)

### Question ###
What is the 20 year for Nitrous Oxide?

### Accurate SQL ###

SELECT 20 AS _yr FROM table_21350772_2 WHERE gas_name = "Nitrous oxide"