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We have to reduce emissions dramatically, to near zero, by sometime around the end of this century. When do we have to start? Does it make sense to wait or should we start now?

Climate Change Is an Energy Problem

To try to get a handle on how to transition to zero emissions, we need to understand where emissions come from and what it means to dramatically reduce emissions. I will focus on emissions of CO2. Reducing emissions of other greenhouse gases like methane and nitrous oxide will also be important but the dominant long-lived greenhouse gas is CO2.

The overwhelming source of CO2 emissions is fossil fuels. Fossil fuels are chains of carbon molecules (plus other things) stored underground. When we burn fossil fuels to create energy, we take the carbon that had been underground and put it in the atmosphere.

Solving the problem of climate change means not doing this, not taking carbon from underground and putting it in the atmosphere. It might be possible to prevent the carbon from fossil fuel use from entering the atmosphere by capturing it when we burn the fossil fuels and then storing it underground. So far this technology has proven expensive and implementing it at scale appears to face possibly insurmountable problems because of the difficulties of transporting the CO2 and of finding safe places to store it. Absent feasible capture technology, solving the problem of climate change means eliminating the use of fossil fuels.

Unfortunately, eliminating or even substantially reducing the use of fossil fuels is going to be difficult. The reason is that energy is central to the global economy and fossil fuels are the central source of energy. Energy’s sheer pervasiveness and reliability makes it easy to ignore, but almost everything we do relies on energy. We take it for granted that our homes are heated, cooled, and lit, and we can get to work, take hot showers, refrigerate our food, have concrete and steel to use for construction, and can obtain products from far away. All of these activities rely on energy. It is not too far from the truth to say that the Industrial Revolution and the basis of modern living arose from new ways to transform energy into useful products. It is easy to miss this because our energy system is so utterly reliable and pervasive that it is invisible.

Figure 6.2 shows the connection between wealth and energy. The horizontal axis shows per capita income for 167 countries (on a logarithmic scale, so that equal increments represent equal percent increases in income). The vertical axis shows energy use per person, using a standard unit known as oil equivalents, also on a logarithmic scale.

The graph shows what we might call the iron law of wealth: increased wealth means increased energy use. While there is some dispersion at the low end (we can be poor with different amounts of energy use), and some rich countries manage to be particularly inefficient, nobody escapes the ironclad relationship between energy and wealth. No nation, regardless of its political system, culture, or fantastic environmental values, has discovered a way to be wealthy without energy use.9 There is nobody in the bottom right hand corner.

Income vs. Energy Use (Log Scales) 2007. Source

figure 6.2 Income vs. Energy Use (Log Scales) 2007. Source: World Bank data.

The bad news is that almost all of this energy comes from fossil fuels. Globally, 87% of energy comes from fossil fuels. Nuclear energy is about 5% and hydroelectric energy is 6.4%. Only 1.6% of energy comes from renewable sources, such as wind or solar.10

The central dilemma of climate change is straightforward: emissions have to go to zero while energy use remains high. We have to find a way to replace 87% of the global energy supply with clean energy. This is not just a developed world problem. If developing countries are to have a standard of living the same as the developed world, something we should hope for, everyone will need carbon- free sources of energy. The problem is replacing developed world energy systems and building developing world systems with clean energy.

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