The US Energy Information Administration’s April 30th Today In Energy post presented a graph similar to the one shown here. The figure compares CO2 emissions with and without the extension of policies that encourage conservation and promote low-carbon energy production. The figure shows that extending existing policies (orange line) reduces CO2 emissions relative to the reference, no extension case (blue line).
Total Energy-Related CO2 Emissions
To emphasis the positive impact of existing policy, cumulative CO2 savings from 2013-2040 is also graphed (purple line). The data is presented with relatively little comment, but the use of the cumulative curve to show that the extended case reduces emissions by over 4.6 billion metric tons puts a positive spin on current policy.
Reducing emissions by over 4,600,000,000 metric tons certainly sounds good. Taken in isolation it gives the impression that we are on a promising trajectory. Unfortunately, 4.6 billion is a terribly small number in relation to what is needed if we hope to avoid a greater than 2 degree increase in global temperature.
To put the Energy Information Administration data into greater context, I added two more scenarios (click green boxes to view):
- Copenhagen Target – In the 2010 Copenhagen Accord, the US committed to reducing emissions to 17% of 2005 levels by 2020. To compare the reference case to one in which the U.S. met the Copenhagen commitment, I generated the path needed for emissions to drop to 17% of 2005 levels by 2020 and then hold steady at this level (~5 billion mt) into the future (green line). Cumulative savings under this scenario are over 10 billion mt (brown line).
- Greater reductions by 2050 – A 17% reduction by 2020 won’t be enough to keep global temperature increases below the 2 degree target. To avoid the worst of global warming we need to reduce emissions by more than 80% by 2050. To compare this to the reference case, I graphed a 4th case in which the U.S. meets the 2020 target then stays on track to lower emissions to 80% of 2005 levels by 2050 (red line). Under this scenario cumulative CO2 emissions are more than 37 billion mt lower than the reference case (pink line).
This added context shows that the 4.6 billion mt reduction realized by extending existing policy is far from adequate to mitigate the worst of global warming. It is not even sufficient to meet the U.S. commitments in the Copenhagen Accord.
Carbon dioxide is not the only greenhouse gas contributing to anthropogenic global warming. For a more comprehensive discussion of US policy related to all greenhouse gases see the World Resources Institute report: Can the U.S. Get There From Here?. For a complete list of the greenhouse gases of concern see the EPA’s Greenhouse Gas Inventory.
The data and calculations used to generate the figure are available as a Google Spreadsheet.