This paper builds a two-country (North, South), two-sector (polluting, nonpolluting) trade model with directed technical change, examining whether unilateral environmental policies can ensure sustainable growth. The polluting good is produced with a clean and a dirty input. A temporary Northern policy combining clean research subsidies and a trade tax can ensure sustainable growth but Northern carbon taxes alone cannot. Trade and directed technical change accelerate environmental degradation either under laissez-faire, or if the North implements carbon taxes, yet both help reduce environmental degradation under the appropriate unilateral policy. I characterize the optimal unilateral policy analytically and numerically using calibrated simulations.