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Given President Obama’s recent declaration that the new course of energy policy may come in the form of “chunks” rather than comprehensive legislation, we must ask ourselves which chunks to push for first if we want better emission outcomes? In order to answer this question, it is necessary to better understand the emissions profile of each sector and how these emissions behave over time. Carbon may be the main culprit, but it works alongside a number of accomplices, each uniquely impacting the climate through distinct “cooling” and/or “warming” effects. The interactions and lifespans of all these chemical species in the atmosphere determine the severity and longevity of any set of emissions from a given fuel or sector of the economy. Thus, the end result, referred to in the scientific community as “radiative forcing,” is complexly determined by the sum of parts. Luckily, a body of critical but under-appreciated research is emerging from scientists at NASA’s Goddard Institute for Space Studies that addresses these complexities.
In one recent paper, researchers applied a climate model to estimate the impact of thirteen sectors of the economy on the climate in both the short run (2020) and long run (2100). As noted by climate policy specialist Deborah Gordon in a review of the research, “breaking the massive energy sector into its sub-sectors is the key because each produces a different, complex mixture of direct GHGs and air pollutant precursor emissions.” Some of these emission species – such as tropospheric ozone and diesel-derived “black carbon” – have exclusively warming effects, while other pollutants – particularly aerosols and sulfates – have a countervailing cooling impact.
In examining the above chart, one can see that the burning of fossil fuels with high sulfur contents such as coal can actually produce significant cooling through the release of sulfates which temporarily block solar radiation and increase cloud longevity and brightness. In the short term, these sulfates outweigh the effects of carbon dioxide, and thus minimize the contributions of coal-intensive sectors such as industry to radiative forcing over a 10 year time horizon.
While a complete neglect of long-term timeframes would be myopic, and many of these cooling species have otherwise undesirable environmental impacts related to public health and local air pollution, an eye towards the short-term implications of sectoral emissions can be useful in identifying starting points for policy action. Furthermore, turning our attention toward sectors with large net-warming impacts throughout the next 100 years may provide the most leverage in avoiding so-called “climate tipping points” that threaten to exponentially accelerate the repercussions of global warming.
As evidenced in the above figure, on-road transportation is an attractive sector to address should legislative progress on the power sector stagnate, and transportation reform is a necessary complement to a comprehensive energy agenda in any case. This is one reason why much of my current work at the Carnegie Endowment focuses on ensuring that the upcoming 5-year re-authorization of the transportation program in 2011 is mindful of the interplay between mobility, economic growth, and energy/environmental security. Cars and light trucks accounted for almost 84% of transportation petroleum use in 2008, and the fourth assessment report of the IPCC found that between 1970 and 2004 the global transportation sector was responsible for the most significant increase in GHG emissions, with a 120% jump.
A good question to ask, then, is where the change will come from? Should we electrify our vehicle fleet and then focus our energies on eliminating coal and other dirty fuels from the power sector? Should we take the approach of Senator Reid, whose proposed legislation would incentivize certain users of the transportation system such as long-haul truckers to convert to natural gas vehicles? Or would it be better to address the structure of the program itself, turning the rudder of a monolithic $76 billion ship that for too long has encouraged sprawl and highway expansion over smarter growth?
In the search for answers, it will be important to think creatively about the policy implications of this research. One of the largest obstacles to comprehensive climate legislation in the past has been so-called “coal state” legislators that view the transition away from fossil fuels and towards clean energy as a threat to the economic viabilities of their states. This is a bloc that in many ways defies partisan boundaries, as Democrats such as Joe Manchin and Jay Rockefeller have been amongst the most outspoken against new EPA power plant regulations. If the issue of coal were to be set aside in the short term, could we in exchange foster broad support for an aggressive transportation bill? Perhaps this would be an imprudent trade-off, but it may also be a strategic way to pick the low-hanging fruit while still allowing cheap and abundant natural gas to slowly displace coal in the meantime.
This is a discussion worth having and the NASA research is material worth studying. I encourage others to engage with these ideas and look forward to exploring further the notion that perhaps the energy revolution begins with a spark in the gas tank.
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David Livingston is a Contributor with Americans for Energy Leadership (AEL). The views expressed are those of the author and do not necessarily reflect the position of AEL.
