Climate change as a global challenge has evolved through a series of stages in the last few decades. We are now on the brink of a new era which will see the terms of the debate shift once again. The different eras are characterised by the scientific evidence, public perceptions, responses and engagement of different groups to address the problem. In the first era, from the late 1980s to 2000, climate change was seen as an "environmental" problem to do with prevention of future impacts on the planet's climate systems over the next fifty to hundred years, through reductions in emissions of greenhouse gases, known as "mitigation". The second era can be said to have started around the turn of the millennium, with the recognition that there will be some unavoidable impacts from climate change in the near term (over the next decade or two). These impacts must be coped with through "adaptation", as well as mitigation, to prevent much more severe and possibly catastrophic impacts in the longer term. It has become clear that many of the impacts of climate change in the near term are likely to fall on the poorest countries and communities. The third era, which we are just about to enter, will see the issue change from tackling an environmental or development problem to a question of "global justice". It will engage with a much wider array of citizens from around the world than previous eras.
