This article substantiates the common intuition that it is wrong to contribute to dangerous climate change for no significant reason. To advance this claim, I first propose a basic principle that one has the moral obligation to act in accordance with the weight of moral reasons. I further claim that there are significant moral reasons for individuals not to emit greenhouse gases, as many other climate ethicists have already argued. Then, I assert that there are often no significant moral (or (...) excusing) reasons to emit greenhouse gases. In any such trivial-cost – but not necessarily trivial-impact – cases, the individual then has an obligation to refrain. Finally, I apply the moral weighing principle to everyday situations of emitting and establish two surprisingly substantial implications: the relevance of virtues to the interpersonal assessment of environmentally harmful actions and the extensive individual ethical obligations that exist short of moral purity. (shrink)