In The Skeptical Environmentalist, Bjørn Lomborg estimates the cost of global warming vs. the cost of limiting CO2 emissions by various schemes. All numbers are in the trillions, but he rather lost me in how those numbers are calculated. Then he comes up with an “optimal” method, which minimizes the costs.
Can anyone help me understand where those numbers came from?
I haven’t read the book, but most calculations of total cost evaluate known and estimated costs of the range of different greenhouse gas mitigation approaches that are likely to be used. If you start with something like compact fluorescent light bulbs, the long-term costs are actually negative, meaning that you save money over the life of the bulb. Many energy efficiency measures are also negative-cost, and have the added benefit of reducing other air pollutants. At some point, you run out of the cheap and easy approaches, and start applying more costly technologies like carbon capture systems. Those tend to cost quite a bit more, with estimates running from $20-$100+ per ton of CO2 removed. On a global scale, the costs can add up quickly. For these technologies that have yet to be used on any significant scale, the cost estimates can be pretty speculative, and it’s unclear whether the costs would be higher or lower. Good arguments can be made either way.
Another issue is estimating how much CO2 would need to be removed. This depends upon population and economic growth for different sectors and what technologies are used in the growth of those sectors. A good discussion of the possible scenarios and costs of mitigation can be found in a report by McKinsey (it’s a 4 MB pdf).
As for estimating the cost of global warming, just off the top of my head, you’d have to estimate the cost of relocating people in low-lying coastal areas, and you’d have increased use of air conditioning. Marginal farming land in very hot areas (like Africa) might become uselessly arid, but this would be offset by gains in the north, where areas that are currently too cold to farm would become more temperate. You might also take into account things like the decline in the skiing industry that would surely occur.