Global warming avoided by hypothetical Gen IV reactors

These are comments I made on the Neurologica blog, regarding the global warming avoided by entirely hypothetical Gen IV reactors potentially being built in the U.S.

Part 1 of 2: I wrote:

Even if--by some frankly unbelievable circumstance--enough Gen IV reactors would be built in the U.S. by 2060 to provide 30% of U.S. electricity, it would have essentially zero effect on global temperatures by the year 2100. (By that, I mean less than 0.01 degree Celsius, though I haven't calculated a particular value.)

Here's a calculation.

1) In 2018, approximately 100 nuclear reactors in the U.S. provided approximately 20% of the electrical energy generated. For simplicity, let's say that approximately 150 Gen IV reactors would produce approximately 30 percent of the electricity generated in 2060. (This essentially assumes that electrical generation in 2060 is the same in as in 2018, and average reactor sizes and capacity factors are also the same.)

2) Before we calculate the global warming effects, let's look at the simple arithmetic of years and number of reactors. No commercial Gen IV reactor is going to go online before 2030. To get 150 Gen IV reactors by 2050, that would be taking online 7.5 Gen IV reactors a year, every year, for 20 years. To get the 150 Gen IV reactors by 2060, it would be 5 Gen IV reactors a year, every year, for 30 years. There is essentially no chance of either scenario happening. And I'm happy to put my money where my mouth is. Steven Novella, I will be happy to bet you $10, and give you 100-to-1 odds, that 150 Gen IV reactors won't be operating in the U.S. by 2050, and happy to bet you another $10, and give you 50-to-1 odds, that 150 Gen IV reactors won't even be operating in the U.S. by 2060. So if 150 Gen IV reactors are operating by 2050, I would pay you $1500 (because I would lose both bets). And if 150 Gen IV reactors aren't operating by 2050, you'd pay me $10, and an additional $10 if 150 Gen IV reactors still aren't operating by 2060.

3) For global warming effects, let's assume an equilibrium climate sensitivity of 3 degrees Celsius per doubling of CO2. That means increasing from 400 ppm to 800 ppm would eventually result in 3 degrees Celsius of temperature change. Each ppm of CO2 is approximately 7.8 gigatonnes of CO2. So approximately 3120 gigatonnes of CO2 results in 3 degrees of temperature change. So one gigatonne of CO2 results in 3/3120 = approximately 0.001 degrees Celsius temperature rise.

3a) An analysis of the warming in the RCP 8.5 scenario yields the following results by comparison: From Wikipedia, median warming in the RCP 8.5 scenario is 3.7 degrees Celsius over the 95 years from 1996 to 2091. Emissions during the 21st century in that scenario are 1932 GtC...or 7084 gigatonnes of CO2. In 95 years, that would be 1835 GtC, or 6728 gigatonnes CO2. So one gigatonne of CO2 results in 3.7/6728 = approximately 0.00055 degrees Celsius temperature rise.

Part 2 of 2

4) Let's further assume that the Gen IV reactors displace natural gas and coal in the percentages that existed in 2018. In 2018, 1468 billion kWh of U.S. electricity was from natural gas, resulting in 581 million metric tons of CO2 emissions, and 1146 billion kWh was from coal, resulting in 1150 million metric tons of CO2 emissions. So a total of 2614 billion kWh resulting in a total of 1731 million metric tons (1.731 gigatonnes of CO2 emissions).

5) Nuclear generated 807 billion kWh in 2018 (20% of U.S. total). We're saying that 30% of electricity in 2050 is from Gen IV reactors, so that's 1210 billion kWh. That means that 1210/2614 x 1.731 = 0.80 gigatonnes of CO2 will be avoided each year by the (entirely hypothetical) Gen IV reactors. That will result in 0.80 x 0.001 = 0.0008 degrees Celsius of temperature increase avoided each year, using the equilibrium climate sensitivity method, and 0.80 x 0.00055 = 0.00044 degrees Celsius of temperature increase avoided each year, based on the RCP 8.5 projections.

7) Using the equilibrium climate sensitivity method: From 2060 to 2100, the avoided temperature increase from approximately 150 Gen IV reactors in the U.S. generating approximately 30 percent of U.S. electricity and entirely displacing coal and natural gas would be 0.0008 deg C per year times 40 years = 0.032 degrees Celsius of global warming avoided. There's also the amount avoided in the buildup from 0 to 30% of electricity from 2030 to 2060...that's equivalent to a total of 0.012 degrees Celsius of global warming avoided.
So I wrote that less than 0.01 deg Celsius temperature avoided, but it's theoretically more like 0.044 degrees Celsius temperature avoided, using the equilibrium climate sensitivity method. Using the RCP 8.5 scenario results method, the avoided warming is more like 0.024 degrees Celsius.

Conclusion: The point still stands...even building 150 Gen IV reactors in the U.S. by 2060 will have a negligible effect on global temperature in 2100...somewhere between 0.024 degrees Celsius and 0.044 degrees Celsius of temperature increase avoided, which is far less than the year-to-year variation in average global temperature.

Comments

[Nisha]

Its global problem and we have to do something quickly.

[Locutusbrg]

Doesn't all of this presume that that renewable sources will hold their own with energy demand. Shouldn't we take all steps to hold back the increase of fossil fuel carbon into the atmosphere even if the net effect is only no increase in number of fossil fueled electrical plants with ongoing renewable expansion. Will it really damage the renewable industry in any way to have another non carbon source of electricity safer than current outdated commercial nuclear reactor, Will gen IV nuclear power threaten renewable, and with the possibility of improving the problems of nuclear storage why not? We all know carbon pollutants are as dangerous if not more dangerous to humans than current nuclear plants. So this feel like more of an ideological rant about an unbelievable level of perfection to require even trying. Why oppose?