Now that the U. S. Environmental Protection Agency (EPA) has announced intent to find that greenhouse gas emissions (primarily carbon dioxide) from human activities lead to the “endangerment of public health and welfare,” the question arises: What could EPA theoretically do about it? (I’ll leave the politics to others.) In other words, can a U.S.-side agency conceptually protect U.S. citizens from the endangerment of their health and welfare from the global issue of global warming?
It turns out that they cannot do much of anything. EPA is simply saber-rattling to get Congress’s attention. If the agency was forced to actually draw their weapon in battle, they would be holding a rubber sword against a massive and growing global force. The bottom line: the EPA is brandishing only about 0.0033ºC/yr-worth of global temperature influence—and that is only if it managed to shut down all greenhouse gas emissions from U.S. economic activity and keep it that way. All the while, the warming pressure from the rest of the world steadily grows, shrinking the EPA’s already too-small-to-matter arsenal.
This can be understood by simplifying the issue down to the Xs and Os—carbon dioxide emissions and global temperatures.
I’ll cast carbon dioxide emissions in terms of the global temperature change they produce based on a few reasonable (although short of perfect) assumptions and then explore via the back of the envelope the potential impact of any EPA regulations.
Assumption 1: Based on both observations and climate model projections, it takes an increase in the atmospheric concentration of carbon dioxide (CO2) of about 115 parts per million (ppm) to raise the global average temperature about 1ºC. Certainly, there is a lot of quibble room here (like the CO2 effect is logarithmic rather than linear), but this number is not that far off for the current conditions.
Assumption 2:Based upon observations, it takes about 15,500 million metric tons (mmt) of carbon dioxide emissions to raise the atmospheric CO2 concentration 1 ppm. This is based on the observations that show that about half of the human CO2 emissions remain in the atmosphere and that this percentage has stayed relatively constant since good atmospheric concentration measurements began in the late 1950s. The 15,500 number comes from dividing the total global annual CO2 emissions each year by the annual CO2 increase (data available from CDIAC if you want to see for yourself). Again you could nit-pick this (like whether or not global CO2 sinks will continue to grow), but this will work for the time being.
These two assumptions lead to the generality that it takes about 15,500 mmtCO2/ppm times 115 ppm/ºC which equals 1,782,500 mmt of CO2 emissions to produce a global temperature rise of 1ºC.
This is a handy number to have. Every time you see someone touting some action that will lower CO2 emissions (and thus “save the planet” from global warming), you can take their emissions savings (in mmtCO2), divide it by the number above (1,782,500 mmtCO2/ºC) and see just how much of the planet they are saving.
Here I’ll use it to look at what kind of temperature rise is being produced by U.S. emissions and what kind of temperature rise is being produced by the rest of the world (over which the U.S. EPA has no regulatory authority).
In 2006, U.S. CO2 emissions were 5,903 mmtCO2, and the emissions from the rest of the world totaled 23,292 mmtCO2. So that means, roughly speaking, that with its 20% (and falling) world share, U.S. emissions in 2006 caused about 0.0033ºC (5903÷1,782,500) of global warming while emissions from the rest of the world caused about 0.0131ºC (23,292÷1,782,500). Now, the astute among you may point out that the global temperature didn’t increase by 0.0164ºC from 2005 to 2006—but realize that my analysis is aimed at a general characterization of the influence of CO2 emissions from human activities, and does not include other influences on the earth’s temperature, which, as we have seen over the past decade or so are quite large as they have acted to offset all the warming from CO2 emissions during that time.
Figure 1 shows the results from not just 2006 but for the past 10 years (more specifically 1997-2006 since this is the most recent data available from the Energy Information Administration) from the U.S. and from the rest of the world.
Figure 1. Influence on global temperature from U.S. CO2 emissions (blue) and emissions from the rest of the world (maroon). The overall height of each bar represents the total influence from CO2 emissions on global temperatures (emissions data from the EIA).
Notice a few things. The amount of global warming each year that the U.S. is responsible for averages about 0.0033ºC per year—an amount that has changed little during this 10-yr period. And, at the same time, the amount of global warming contributed by emissions from the rest of the world has increased from about 0.010ºC/yr in the late 1990s to about 0.013ºC/yr during the past couple of years. This means that the percentage of the total warming that the U.S. is responsible for has been declining—which of course, means that the EPA’s ability to mitigate global warming by reigning in U.S. CO2 emissions is waning. In other words, as total emissions from the rest of the world grow at a pace that far exceeds that of the U.S. emissions, the EPA’s ability to protect Americans from the endangerment of their health and welfare diminishes.
Let’s look at it another way. This time, supposing that the EPA had made its endangerment finding in 1997 and issued regulations that (miraculously) eliminated all U.S. CO2 emissions within the proceeding 10 years (i.e. from 1997 to 2006), the chart in Figure 1 would look like this (Figure 2).
Figure 2. Influence on global temperature from U.S. CO2 emissions (blue) and emissions from the rest of the world (maroon) assuming that the EPA instituted regulations in 1997 that reduced the U.S. CO2 emissions to zero by 2006. The overall height of each bar represents the total influence from CO2 emissions on global temperatures.
The net result of this monumental achievement would have been that the EPA would have managed to hold the rate of global warming (total height of the bars) relatively steady during this period—this is not the actual global temperature, mind you, but just how fast it was warming from one year to the next. And most significantly, in doing so, it would have used up all of its chits! Having eliminated all U.S. emissions (whose reductions were being used to offset emissions increases from elsewhere around the world), total global emissions will once again continue their rise and so too will the rate of global temperature increase. And the EPA will be played out.
The only lasting feather in EPA’s cap would be that it managed to eliminate 0.0033ºC of warming each year if it were successful at completely eliminating all U.S. CO2 emissions, forever. It would be mighty interesting to see a quantification of the endangerment that it avoided by doing so. My bet is that it would be embarrassingly small. And the effort to do so would be embarrassingly large.
It is hard to imagine that the EPA couldn’t serve us in far better ways.