Ocean floor deposits and model calculations have confirmed that in the past 3 million years, the global mean temperature has never been more than two degrees above pre-industrial levels, with fluctuating CO2 levels in the atmosphere. Since the beginning of industrialization, more CO2 has accumulated in the atmosphere through the burning of coal, oil and gas than probably ever before in the past 3 million years. Thus, in our current century, there is real threat that without effective climate policy the 2-degree limit of global warming will be breached for the first time – with far-reaching consequences.
