Business will adopt technologies and practices that reduce emissions if it sees economic value in them. That value becomes clearest when carbon has a credible price based on a mechanism that is stable over the long term (see figure 5). To minimize competitive distortion, the price should ultimately be global. Trading with emission rights is well suited to give such a price signal, because it creates minimal distortion in the market, facilitates inclusion of multiple countries and is easy to link to a target emission cap. The sooner governments and businesses establish a global emissions trading system the better, but, realistically, any international system will have to be introduced stepwise.