In the late 1980s, an intensive debate began about the influence of human activities on climate system. Although substantial resources have been expended on this issue, the debate is no closer to being resolved. Science still can not distinguish human influence from natural variability with a high degree of confidence. Over the past two decades, we have gained knowledge but our understanding is still meager. While we now know that the climate system is more complex than previously assumed, we also know that our understanding of it is less than assumed.
There are basically two parts to the debate. The first is about climate science and what it tells us about how the climate system operates and the influence of human activity on it. The primary concern is carbon dioxide (CO2) which is mainly the result of using fossil fuels. I do not address the science issues but accept the view that enough is known to make human induced climate change a legitimate cause of concern and prudent action.
The second part, and my focus, is what nations do to address the risk of human induced climate change, the potential impacts of those actions and the realistic constraints on actions —“the objective realities”. The second part is primarily political.