"they are by far and away one of the largest contributors to greenhouse gasses as a group."
Wrong. Shipping is the most efficient transportation of mass-distance per unit of CO2. Shipping's CO2 contribution is only %3-%4 of total CO2 produced by humans.
Wrong. Shipping is the most efficient transportation of mass-distance per unit of CO2. Shipping's CO2 contribution is only %3-%4 of total CO2 produced by humans.