How sure are we about the phenomenon of climate change of human origin? What is this global threat? Are there scientists and institutions that deny its existence? Are its effects already seen and felt? Will the economy go bankrupt trying to stop or reverse climate change? Do we already have enough technologies for the huge greenhouse gas emission reductions required? Why is stopping deforestation so important? What to do with the impacts that will inevitably occur, even if we are successful with mitigation? These are some of the questions that this book tries to solve, which, to facilitate and make it more pleasant for the reader, is organized in the form of a question - answer. It is a text of simple reading, which is based on the best available knowledge, in order to approach what is, perhaps, the problem with the most complex solution of all time - judged from the economic, social, technological and political perspectives - and that, for this reason, it is difficult for citizens to understand. It is a problem that, for twenty years, has led the countries of the world to try to solve it through a global agreement, which is expressed today in the context of the Copenhagen Conference and the negotiations that follow.