A global monopoly supplier country of green goods which are essential for the provision of global environmental public goods optimally subsidizes the export of such goods in an interior contribution equilibrium. This is not counterbalanced by an incentive to improve the terms-of-trade, since any price-induced transfers are off-set by contribution adjustments. By the same logic, a subsidy is costless for the monopoly supplier. The existence of a global monopoly supplier increases global public good supply relative to a competitive setting. The incentive to subsidize persists with impure public goods as long as the private co-benefits of green goods are sufficiently easy to substitute by other goods. Import-dependent countries may also benefit from a monopoly supplier. While they are strategically exploited to increase their contributions to the global public good, they do so at lower costs, and they benefit from increased contributions by the other importer countries.