It is clear that reduction on the necessary scale—to cut emissions by a factor of 2.5 in the next four decades (from global emissions of around 50 billion tonnes CO₂e in 2010 to below 20 billion tonnes CO₂e, and from around 7 tonnes per capita on average in 2010 to around 2 tonnes CO₂e per capita)—requires all countries to be involved: it is not a task that any country can do alone.

If, in 2050, 2.5 billion people (the likely population of China, the US, and the EU) of the around 9 billion people were on average emitting 8 tonnes per capita, then the other 6.5 billion would have to be emitting below zero on average. At present, the US emits around 20 tonnes per capita and China is likely around 9 and rising. Looked at from another angle, if India and Africa, likely to be around 3 billion people or more in 2050, were at 7 tonnes per capita, quite likely on current trajectories, the other 6 billion or so of the world's population, including China, the US, and the EU, would have to be at zero or below.

These calculations are not morally or economically prescriptive. They take no account of the history of emissions or of income per capita. They simply illustrate the immensely important quantitative point that the scale of the necessary change is such that all countries must be involved in strong cutbacks of emissions. We shall argue that this can and must be consistent with overcoming poverty and with development and growth. That is the recurrent theme of this book.

– Page 40

Embracing a broad range of technologies for the transition makes sense. We cannot predict with certainty how costs will change. Different technologies provide different energy profiles—for example, nuclear provides primarily base load—and contribute to a system in different ways. Ruling out technologies may turn out to raise costs of the transition in the longer run and increase vulnerabilities. A portfolio approach seems wise. But support for some low-carbon technologies can change, as can perception of their risk. The Fukushima Daiichi nuclear disaster in 2011 shifted public perceptions on nuclear power across the world, with major adjustments to energy policy in some countries in the weeks and months following. Public opposition to nuclear energy in Italy and Germany strengthened considerably; Germany decided to close several older nuclear plants immediately and committed to a total phase-out of nuclear by 2022. In Italy, a referendum on nuclear energy was held just months after Fukushima, with 94% of the electorate (in a high voter turnout of around 55%) voting for a ban on construction of new plants.

Evidence suggests that changes in attitudes and perceptions following events like Fukushima may be temporary. Whether opposition proves to be temporary or persistent, rapid policy adjustments caused by such events may have wide-ranging and often unexpected implications. Germany's policy shift has seen greater coal use. And as more nuclear plants shut over the coming years, it is likely that coal will fill a large part of the gap, with 12 new plants planned by 20202. The lesson is that a relatively rapid phasing-out of low-carbon plant (here nuclear) has significant implications, with, in Germany's case, increasing emissions and possible medium- or long-term lock-in to unabated coal.

– Page 124