Part 3 of 4: U.S. Emissions Target

This is the third installment of a four-part series to be published each Wednesday on Action Needed to Stop Global Warming.

1. How Warm is Too Warm?
2. Worldwide Emissions Target
3. U.S. Emissions Target
4. Technologies to Get Us There


In Part 1 of this series, I defined the global tipping point as the melting of the Greenland ice sheet, which could cause sea levels to rise 20 feet. In Part 2, I showed by how much global emissions of carbon dioxide (CO2) must drop to avoid this tipping point. They must start to decline around 2020, drop 50 percent by 2050, and drop at least 75 percent by the end of the century.

Meeting these global emissions targets will require a global effort. Even if the U.S. and other developed countries were to cut their emissions to zero, global emissions would likely exceed the targets by mid-century. This is because of the rapid rise in emissions from China and other developing countries.

So both developed and developing countries must participate, but how much of the burden should each bear? We could require all countries to make the same emission cuts at the same time, but many believe that would be neither realistic nor fair.

Although the U.S. can’t solve the problem alone, its participation is crucial because the U.S. is the single largest CO2 emitter. China is a close second and rapidly catching up – but only if we consider current emissions.

If we look at historical or accumulated emissions, the dominant role of the U.S. is even more apparent. The U.S. is responsible for almost 30 percent of accumulated emissions in the atmosphere today; China is responsible for only 8 percent. If we look at emissions per person, the distribution is even more lopsided: the U.S. emits about six times more than China.

Graph adapted from J. Hansen presentation.

Developed countries have the resources to cut emissions immediately without damaging their economies. It’s therefore reasonable to expect them to take the lead. Some of the bills currently before Congress recognize this, and would have the U.S. cut emissions almost immediately, so that total emissions are capped at 10 to 30 percent below current emissions in 2020, and 60 to 80 percent by 2050.

Note that the cut for the U.S. of 60 to 80 percent by 2050 is higher than the global requirement of 50 percent by 2050, and the U.S. peak in 2008 is earlier than the global requirement of 2020. This allows developing countries like China to take more time to drop their emissions so their vulnerable economies aren’t over-burdened. But it doesn’t give them a free ride. The growth rate of emissions in developing countries would have to slow almost immediately, then around 2025 emissions would begin to decrease at a rate comparable to that of developed countries. The challenge for the global community in the “son of Kyoto” negotiations will be to get both developed and developing countries to commit to this scenario.

Next week, in the last part of this series, I’ll talk about the technologies we can use to meet these emissions targets.

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7 Trackbacks

  • […] Part 3 of 4: U.S. Emissions Target […]

  • […] Intensity targets are a smokescreen for inaction because they don't guarantee that emissions will go down. As Dr. Chameides described in his series "Action Needed to Stop Global Warming" emissions have to decrease (substantially!) to avoid dangerous climate change. […]

  • […] In Part 3 of my series on "Action Needed to Stop Global Warming", I discussed what the U.S. emissions target needs to be and why. To do its part in stopping global warming, the U.S. must reduce emissions 10 to 30 percent below current emissions by 2020, and 60 to 80 percent by 2050. Note that this is an absolute reduction, not a decrease in the growth rate. […]

  • […] How Warm is Too Warm? 2. Worldwide Emissions Target 3. U.S. Emissions Target 4. Technologies to Get Us There In Part 1 of this series, we described whyscientists and policy-makers have identified the melting of the Greenland ice sheet, which would lead to a 20-foot rise in sea level, as the tipping point that must not be crossed. To stay below the tipping point, average global temperatures must not rise more than 3.6oF above pre-industrial temperatures, or 2.3oF above current temperatures.Today we consider how global emissions of greenhouse gases must change over the coming century to stay below that tipping point. […]

  • […] The bill will cap greenhouse gas emissions at 1990 levels by 2020, and lower the cap to 80 percent below current levels by 2050 (see New York Times article). It is the first bill in the nation to legislate a 2050 target. This is important because 2050 targets are crucial to avoiding the global warming tipping point, and are a component of the bills currently before Congress. When forward-looking states pass legislation like this, it can force the federal government to do likewise. […]

  • […] As Bill Chameides pointed out in his post on the U.S. Emissions Target, the U.S. must cut emissions below current levels by 60 to 80 percent by 2050. These bills cut emissions below current levels by 0 percent. […]

  • […] long-term target in the Lieberman-Warner Climate Security Act is not at the level that the best science recommends, but its near-term cap is aggressive – more aggressive than any other proposal currently filed with […]