The world is changing but not quite fast enough. The warming of the Earth, caused by rising greenhouse gas emissions, has raised enough concern among the political leaders of the world for them to finally take action. The Paris Agreement, now ratified by 168 member states within the United Nations Framework Convention on Climate Change (UNFCCC), has set the ambitious goal of radically reducing greenhouse gas emissions until the middle of this century. The aim is to confine the increase in mean worldwide temperatures to less than 2 °C above preindustrial levels, and possibly only 1.5 °C. But scientists are warning that greenhouse gas emissions are still increasing and will continue to do so for some years to come – maybe so much that the 2 °C limit will be impossible to maintain and substantially higher mean temperatures will be reached.