If the US embarked on a similar plan, the cost and the benefit would probably be on a similar scale: a two-centimeter reduction in sea-level rise by the end of the century at a net cost of about $500 billion annually.Consider this extremely unrealistic scenario: even if we almost immediately could get the entire world – including China and India – on board for drastic carbon cuts, and even if we would suck CO2 out of the atmosphere toward the end of the century, we could reduce sea level rise by only 18-45 centimeters by the end of the century.