If rich countries introduce domestic carbon taxes or auction emissions permits based on this price level, they could potentially provide $30 billion a year for developing countries by using just 10% of the revenues. A carbon tax on international shipping and aviation set at the same level (or auction revenues from emissions caps, if that pricing route is followed) could generate $10 billion annually for international climate action from just 25-50% of the revenues, even after ensuring that costs borne by developing countries are covered.