How Does Black Carbon Change the Climate Debate? [ PDF ]

In this Newsletter:

Reassessing Responsibilities

Fran Moore, Yale School of Forestry and Environmental Studies

As laid out in other articles in this issue, it is increasingly apparent that black carbon is playing an important role in global climate change and, because of its short lifetime, offers substantial opportunities to reduce radiative forcing. In a paper published in 2009, Michael MacCracken and I outlined the ‘lifetime leveraging’ proposal – a framework for an effective climate change agreement in which high-income countries commit to substantial reductions of all greenhouse gases while middle-income nations work to reduce short-lived greenhouse gases such as black carbon, methane and ozone until they are rich enough to begin reducing CO2 emissions.

This article evaluates the lifetime leveraging proposal with respect to the UNFCCC principle that mitigation burdens should be shared according to the common but differentiated responsibility and respective capabilities of nations. This principle is reiterated in the Berlin Mandate (1995, paragraph 1), the Kyoto Protocol (1997, Article 10), the Marrakesh Accords (2001, paragraphs D and H) and the Bali Roadmap (2006, paragraph 1).

Responsibility

The common but differentiated responsibility (CBDR) principle has become near-universal in mitigation burden sharing proposals. Despite its ubiquity, multiple metrics for responsibility have been put forward by countries. Figure 5 shows three of the more commonly used responsibility metrics for fossil fuel CO2 emissions and closed combustion black carbon emissions: absolute emissions, per-capita emissions, and emissions intensity. Emissions from land use changes and open burning are excluded.

Figure 5A

Figure 5B

Figure 5C

Figure 5. A: per-capita CO2 and black carbon emissions. B: absolute emissions. C: CO2 and black carbon intensity (normalized by GDP). (Bond, et al., 2007; WRI, 2008).

The first graph (figure 5A) shows per-capita emissions for both CO2 and black carbon. It is interesting in that a key feature of the climate change problem, namely up to an order of magnitude difference in per-capita CO2 emissions between developed and developing countries, is not reproduced in the black carbon graph. Instead, per-capita black carbon emissions in all regions are roughly comparable. In particular, developing regions such as Asia and sub-Saharan Africa have the same per-capita black carbon emissions as Europe. This homogeneity in per-capita black carbon emissions, in contrast to CO2 emissions, results from the fact that abatement technologies have been developed and deployed in high-income countries during industrialization because of air pollution concerns.

Assigning responsibility solely on the basis of absolute emissions would again result in North America and Europe having high responsibility for CO2 emissions but far lower responsibility for black carbon. Asia is responsible for high-levels of both while South America and sub-Saharan African release minimal levels of both. In the context of this paper it is interesting to note the relative responsibilities for CO2 and black carbon emissions. So while North America, Europe and Asia are responsible for roughly equal proportions of total CO2 emissions (30-40 percent), Asia is responsible for a far greater proportion of the black carbon emissions (59 percent) than either Europe (12 percent) or North America (9 percent). Similarly, Africa is responsible for less than one percent of CO2 emissions but just under 10 percent of black carbon emissions.

Using the carbon intensity metric shows low responsibility in the service-based economies of North America and Europe but high responsibility in both Asia and Africa. The intensity metric, however, is of dubious use as an indicator of responsibility because it obscures the historical increase in greenhouse gas emissions associated with GDP growth, which is a key structural fact of the climate change problem. Nevertheless, comparing the most efficient with the least efficient gives an impression of the scope for improvement. So a unit of wealth produced in Asia is associated with 3.5 times more CO2 emissions but with almost 20 times more black carbon emissions than an equivalent unit produced in North America, suggesting significant scope for black carbon emission reduction.

Most importantly, all responsibility metrics show the developing world as relatively more responsible for black carbon than for the CO2 problem. In the face of mitigation resource constraints, this finding suggests that it is fair for mitigation actions to be differentiated according to the ‘lifetime-leveraging’ proposal so that developed nations work on reducing long-lived greenhouse gas emissions and industrializing nations work on short-lived emissions and particularly black carbon.

Capability

Although less frequently cited as a principle of mitigation burden sharing than CBDR, differentiating responsibilities based on ‘respective capabilities’ is also an important principle of the Convention. The principle finds its roots in a long-standing and fundamental tradition of international environmental policy – that developing nations should not have to sacrifice scarce resources to environmental improvement in the face of more pressing basic development needs. Implementation of this principle has seen many international environmental treaties include temporary exemptions for developing countries or financial transfers from the North to the South to aid compliance with commitments.

Figure 3 shows the historical trends in black carbon emissions, particularly the differences between developed and developing regions. Technologies to reduce black carbon (and to a lesser extent tropospheric ozone) have already been developed and deployed in the United States in order to abate air pollution, resulting in a reduction of black carbon emissions by over half between 1950 and 2000 and by almost three quarters since emissions peaked in 1920. Similar declines have occurred in Western Europe since the 1950s. In contrast, no developed nation has managed to truly bring fossil fuel CO2 emissions under control and there are no examples of large, wealthy countries with per-capita emissions low enough to be considered sustainable. In other words, it is as yet unclear what a low carbon society with a high standard of living would look like, which is not the case for short-lived greenhouse gases that are also air pollutants.

The fact that air pollution abatement technologies were deployed in the North long before global warming became a serious policy concern speaks to another element of the capability principle. Pollution control confers benefits as well as costs and a country is more capable of controlling pollution to the extent that it can benefit from those efforts – not only does it make it more economically beneficial, but also more politically feasible in that measures can be justified to constituents on the basis of local environmental improvements. Table 1 compares the geographical and temporal distribution of direct benefits from the abatement of black carbon and fossil-fuel CO2 emissions. Industrializing countries will be more capable of mitigation to the extent that a greater fraction of benefits occur locally and immediately as opposed to globally in the distant future.

		Local	Regional	Global
Black Carbon and O3	Benefit:	Reduced morbidity and mortality from indoor and urban air pollution.	Reduced ABC formation and associated glacier melt, monsoonal disruption and surface dimming.	Reduced impacts from global climate change.
	Relative Magnitude:	Substantial	Small to moderate	Moderate
	Time Scale:	Immediate	Immediate to decadal	Multi-decadal
Fossil Fuel CO2	Benefit:	None	None	Reduced impacts from global climate change.
	Relative Magnitude:	NA	NA	Very Substantial
	Time Scale:	NA	NA	Multi-decadal

Table 1. Comparison of the geographical and temporal distribution of benefits for black carbon and fossil fuel CO2 emissions. The magnitude of the benefits is subjectively assessed and is relative to the total benefits for that action. Variations in time scale result from differential responses of different natural systems. Based on Ramanathan (2008) and WHO (2005). (1)

From Table 1, it is clear that abatement of black carbon is a far better fit with the capabilities of industrializing countries in that it would result in an immediately-apparent improvement of local air quality. In fact, governments in developing countries are already implementing policies to improve local air quality: New Delhi is switching the municipal bus system to compressed natural gas to reduce air pollution while Beijing is considering making pollution-control measures implemented for the Olympics permanent. Integrating these existing and emerging air pollution policies with climate change mitigation efforts could both generate significant improvements for the climate and overcome the developed-developing state deadlock in the negotiations.

Conclusion

It is clear from the evidence presented above that middle-income, industrializing countries are both more responsible for black carbon emissions than for fossil-fuel CO2 emissions and are more capable of reducing those emissions. Thus a lifetime-leveraging framework not only is effective in keeping temperatures below 2-2.5 degrees (demonstrated in Moore & MacCracken, 2009), but is also consistent with principles of fairness embodied in the UNFCCC. While this may not mean the proposal is necessarily immediately politically feasible, it does suggest that political hurdles may not be insurmountable.

References

Bond, T., Bhardwaj, E., Dong, R., Jogani, R., Jung, S., Roden, C., et al. (2007). Historical Emissions of Black Carbon and Organic Carbon Aerosol from Energy-Related Combustion, 1850-2000. Global Biogeochemical Cycles, 21, GB2018.

IPCC (2007). Climate Change 2007: Mitigation of Climate Change. New York: Cambridge University Press.

Moore, F., & MacCracken, M. (2009). Lifetime Leveraging: An Approach to Achieving International Agreement and Effective Climate Protection Using Mitigation of Short-Lived Greenhouse Gases. International Journal of Climate Change Strategies and Management, 1(1).

Ramanathan, V., Agrawal, M., Akimoto, H., Aufhanner, M., Devotta, S., & Emberson, L. (2008). Atmospheric Brown Clouds: Regional Assessment Report with Focus on Asia. Nairobi, Kenya: United Nations Environment Programme.

WHO (2005). Indoor Air Pollution and Health (Vol. Fact Sheet 292). Geneva, Switzerland: World Health Organization.

WRI (2008). Climate Analysis Indicator Tool. cait.wri.org

(1) Mitigation of fossil fuel CO2 emissions can have significant side benefits in terms of reduction of co-emitted air pollutants such as sulfates, NOx, and particulate matter (including black carbon; IPCC, 2007, pp. 619-690). The magnitude of these benefits will vary depending on mitigation strategies used. For example, they may be substantial for fuel switching to renewables but minimal for carbon sequestration.

Autumn 2009 Climate Alert

How Does Black Carbon Change the Climate Debate? [ PDF ]

In this Newsletter:

Responsibility

Capability

Conclusion

Other Articles in this Newsletter: