Although the last report of the Intergovernmental Panel on Climate Change has been criticized by The Economist because of too optimistic cost calculations about climate change mitigation, its message is clear once more: unless we act now, the rise in temperatures in our planet by the end of this century may be catastrophic and completely change life as we know it. If The Economist is wrong and the report is right, the costs of acting now are affordable, which means that the global economy may keep growing without causing lasting damage. That is in principle possible: economic growth, as Paul Krugman explains, is not incompatible with respecting the environment. We may grow without consuming material resources, but grow in valuable services, ideas and knowledge. As long as the cost of mitigation is lower than the cost of adaptation without mitigating, which everybody assumes that would be prohibitive, the things to be done demand the creation of institutions adapted to the challenge. These include international cooperation and cooperation at unprecedented levels and the setting up of an international carbon price, be it through taxation, through the exchange of emission permits, or both. These issues will increase in importance in our lives in the next years and decades, and everybody should become knowledgeable about them. Understanding is the first step for action.