The anthropogenous greenhouse effect is in danger of becoming the biggest environmental problem of this century, with enormous negative consequences for mankind. In particular, it threatens to kill hundreds of millions of people. Unfortunately, the economic costs for preventing these consequences, according to traditional economic assessment, are gigantic. In The Greenhouse, Christoph Lumer provides moral evaluations of the greenhouse effect and of some of its alternatives, from utilitarian and welfarist perspectives. Relying on economists' estimates of the social consequences of the greenhouse effect and on psychological information about influences on subjective well being, business as usual and three more or less severe greenhouse gas abatement options are assessed from the points of view of hedonistic utilitarianism and of welfare ethics, which incorporate components of distributive justice. These evaluations and theoretical considerations about moral duties justify moral obligations to deal now, and seriously, with the greenhouse effect.