How uninhabitable will rising carbon dioxide make the world?

It is widely believed that the burning of fossil fuels has increased the CO2 content of the atmosphere (Step 1), which in turn has led to global warming (Step 2), which in turn has caused climate change (Step 3) which is characterized by an increase in the frequency and magnitude of extreme events, which in turn will render parts of the globe uninhabitable (Step 4). Each step in this line of argument is examined. The evidence for the first is good; that for the second very weak (it is difficult to say how much of the observed warming is natural). The third step has no factual basis, and it is demonstrated why it is difficult to determine the frequency of extreme events, let alone any changes in that frequency. Accordingly the fourth step in this line of argument must be regarded as fictional at best. It transpires that, during the time it has taken us to gain a proper understanding of "climate change", the cost of renewable energy has fallen to the point where many renewable technologies are now competitive with fossil power generation. Economics now drives renewables, making them all the more sustainable than they were.