I have bad news. The World Bank released a report last week on global warming. In summary, we are on track for a world that is 4°C warmer by the end of the century and this will have severe adverse effects, particularly for the global poor.
But this is not the bad news.
I used to think that what we need to do about global warming is to re-engineer our energy production so that we can continue our economic growth with vastly lower carbon emissions / BTU. So the solution to global warming was that we had to first shift our energy production away from high emission fossil fuels such as coal toward lower emission fuels such as natural gas and zero-emission sources, such as solar. Eventually, fusion power would allow us to do without fossil fuels for nearly everything except air travel. Or something like that.
We do need to do develop and implement much cleaner energy production technologies. But I have recently encountered an argument that this will not be enough, and I can’t get it out of my head. The argument is from Tom Murphy, a physics professor at UCSD. It’s simple and frightening.
If I burn a stick of wood, some CO2 is released, along with some heat. The earth is warmed in part by solar radiation which is retained in the atmosphere by greenhouse gases. Our current global warming problem stems from the increase in those gases, hence it is a problem that I released some CO2. But what about the heat?
The heat generated by human energy production is not much of a problem right now, because human energy production is small compared to the energy delivered to the earth from sunlight. But look carefully at the figure above, which presents the historical growth in US energy production. The vertical axis is in a log scale, meaning that energy production accelerates exponentially, with a steady annual growth rate of 2.9%. What Murphy points out is that exponential growth in energy consumption must lead to a state in which human generation of heat will dramatically warm the planet, over and above any effects of heat from the sun.
Murphy goes on to show that these effects are coming relatively soon, because energy consumption is accelerating so quickly.
No matter what the technology, a sustained 2.3% energy growth rate would require us to produce as much energy as the entire sun within 1400 years. A word of warning: that power plant is going to run a little warm. Thermodynamics require that if we generated sun-comparable power on Earth, the surface of the Earth—being smaller than that of the sun—would have to be hotter than the surface of the sun!
Of more immediate concern, we produce effects similar to those anticipated from greenhouse-gas-driven warming sometime in the 22nd century.
Thus relatively soon, we need to accept a hard limit on energy consumption on the earth’s surface. That might mean that we have to live in space, radiating away energy. Whatever community remains on Earth, however, must enforce a limit on total energy production. Additional increases in global GDP can occur only through the discovery of energy efficiencies. Contrary to what I used to think, there is no technological pathway that permits a limitless growth of clean energy consumption.
This doesn’t have to be a dystopia. The economic growth we can achieve in the 21st century should be more than enough to give everyone on the planet a fantastically rich life. However, limiting total energy consumption is an even more difficult institutional challenge than limiting greenhouse gas emission. A century is not much time to build a global political community that is mature enough to make the necessary decisions, and to make them justly.