The realization that human beings need to be concerned about the only 'life-support system' that the Earth and its environment provides stems perhaps in part from the fact that, until fairly recently, the evolution of humankind was largely dependent on the quality of the environment and the resources it provides in terms of water, food, and favourable health conditions. These are as vital as ever, despite current levels of technology and apparent resilience in the face of often degraded environments in many parts of the world. Today, the conditions for human sustainability (i.e. water quality and quantity, food security, and health) are potentially under threat as a result of numerous human-induced factors; among these, climate change is certainly one of the more durable aspects of anthropogenic disruptions to natural resources. This article will therefore focus on the possible evolution of climate in the course of the twenty-first century and on a number of key climate impacts that may determine the future course of human societies, as well as issues that may confront them such as rivalries over natural resources and possible environmentally driven conflicts and migrations.