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Human Health Risk and Climate Policy Co-Benefits

What is the influence of economic growth on the co-benefits of decarbonisation?

Economic development of the poorer nations brings competing influences on public health. On the one hand the increase in per capita wealth reduces susceptibility to environmental pollutants. On the other hand, wealth created through industrialisation may increase the emissions of those same pollutants (if the environmental intensity of the economy is not improved to offset growth of that economy).

Global climate policy negotiations have recognised this conflict, striving to identify a pathway to decarbonise the global economy while allowing growth in world regions at the bottom of the economic pyramid. The research underlying this Results Viewer explores the conflict by using a quantitative methodology (the Human Health Module of 4CMR) for calculating economic growth’s net impact on public health and the co-benefits of greenhouse gas reductions associated with exposure to particulate matter. The study shows that co-benefits of decarbonisation are significant; that GDP growth in non-Annex I nations carries its own health benefit that partially offsets the increase in pollution; that co-benefits are also reduced through the increase in GDP by between 12 and 17% (compared to the case where co-benefits calculations do not include the effect of increased wealth); and that failure to include economic growth projections into co-benefits calculations produces greater errors in co-benefits estimates as the stringency of climate policies is increased.

The analysis is based on regressions of risk coefficients against PM2.5 concentration, per capita GDP, Gini (equity index) and rate of urbanisation (UrbRate). Resulting graphs under example conditions are shown in Figures 1 and 2.

 

Figure 1 cobenefits

Figure 1. Plot of PM2.5 concentration (x-axis) versus ERR (y-axis) with GDPpercap = 20000 (USD); UrbRate = 0.54; Gini = 0.4. From the slope of the curve at a value of 100 µg/m3, it can be seen that the Excess Relative Risk (ERR) is approximately 0.002 per µg/m3 for PM2.5, or approximately 0.001 per µg/m3 for PM10.

 

Figure 2 cobenefits

Figure 2. Plot of GDPpercap (x-axis) versus ERR (y-axis) with PM2.5 = 50 µg/m3; UrbRate = 0.54; Gini = 0.4.

 

The results you can view here consider 4 scenarios of economic development and their effects on both carbon emissions and co-benefits. They make use of the Developed-Developing Nations results you will also find under this Results Viewer section of the 4CMR website.

Scenario 0 (baseline): Global population is brought smoothly to an equilibrium value of 10.5 billion, with a reduction in the rate of population growth of 3% per year in all nations (i.e. the reduction during a given year is 3% of the growth rate at the start of the year). Growth rate in per capita emissions in the Annex I and non-Annex I nations continues unabated into the future. The resulting global emission rate of carbon over the period to 2100 is as shown in Figure 3. It produces cumulative global emissions of 1,330 GtC or 4,870 GtCO2 between 2000 and 2100 and therefore fails to meet any of the global climate policy targets by a factor of more than 2. Inflation-adjusted per capita GDP increases by 1% per year in Annex I nations and 5% per year in non-Annex I nations. No changes in the values of UrbRate or Gini are assumed. Only results out to 2050 are used in the current study as these are most relevant in public health debates.

 

Figure 3 cobenefits

Figure 3. Global annual carbon emissions (billion tC/year) under the baseline scenario of no significant carbon emission mitigation policies.

 

Scenario 1: Global population is brought smoothly to an equilibrium value of 10.5 billion, with a reduction in the rate of population growth of 3% per year in all nations. Global emissions are as shown in Figure 4 (left). Global per capita emissions are shown in Figure 5 (left) for the Annex I (blue line) and non-Annex I (red line). The Annex I nations reduce carbon intensity of the economy at 3% per year beginning in 2015. The non-Annex I nations reduce carbon intensity of the economy at 5.2% per year beginning in 2020. The rate of growth of energy demand for Annex I nations is slowed by 4% per year beginning in 2020 (4% of the current rate of growth, not a 4% reduction in energy demand). The rate of growth of energy demand for non-Annex I nations is slowed by 2% per year beginning in 2050 (2% of the current rate of growth, not a 2% reduction in energy demand). Inflation-adjusted per capita GDP increases by 1% per year in Annex I nations and 5% per year in non-Annex I nations. No changes in the values of UrbRate or Gini are assumed.

 

Figure 4 cobenefits

Figure 4. Global annual carbon emissions (billion tC/year) under Scenario 1 (left) and Scenario 2 (right).

 

Figure 5 cobenefits

Figure 5. Per capita annual carbon emissions (tC/person-year) for Annex I (blue) and non-Annex I (red) nations under Scenario 1 (left) and Scenario 2 (right). Note that Scenario 1 brings the per capita emissions of the nations to a common and declining value after 2050 (producing global equity of per capita emissions), while Scenario 2 allows the non-Annex I nations to emit more per capita than do the Annex I nations after 2040 in recognition of historically inequities in emissions.

 

Scenario 2: Global population is brought smoothly to an equilibrium value of 10.5 billion, with a reduction in the rate of population growth of 3% per year in all nations. Global emissions are as shown in Figure 4 (right). Global per capita emissions are shown in Figure 5 (right) for the Annex I (blue line) and non-Annex I (red line). The Annex I nations reduce carbon intensity of the economy at 5% per year beginning in 2015. The non-Annex I nations reduce carbon intensity of the economy at 2% per year beginning in 2050. The rate of growth of energy demand for Annex I nations is slowed by 10% per year beginning in 2020 (10% of the current rate of growth, not a 10% reduction in energy demand). The rate of growth of energy demand for non-Annex I nations is slowed by 1% per year beginning in 2050 (1% of the current rate of growth, not a 1% reduction in energy demand). Inflation-adjusted per capita GDP increases by 1% per year in Annex I nations and 5% per year in non-Annex I nations. No changes in the values of UrbRate or Gini are assumed.

 

Scenario 3: This is a scenario based on Scenario 1 but with more dramatic declines in per capita emissions from the non-Annex I nations after 2020 as shown in Figure 2. Inflation-adjusted per capita GDP increases by 1% per year in Annex I nations and 5% per year in non-Annex I nations. No changes in the values of UrbRate or Gini are assumed.

 

Figure 6 cobenefits

Figure 6. Per capita annual carbon emissions (tC/person-year) for Annex I (blue) and non-Annex I (red) nations under Scenario 3. Note that Scenario 3 brings the per capita emissions of the nations to an approximately common value after 2080, and significantly reduces the cumulative increase in global emissions due to the non-Annex I nations between 2010 and 2050 compared to Scenario 1. 

Results are summarised in Table 1, including now policy Scenario 3, which allows comparison of the total reduction in PM-induced mortality under the three policy scenarios between 2010 and 2050. The value of ‘Total cumulative’ is the total excess mortality globally from 2010 to 2050 for Scenarios 0, 1, 2 and 3, followed by the difference in this value for policy Scenario 1 versus 0, for policy Scenario 2 versus 0 and for policy Scenario 3 versus 0 (i.e. the co-benefits). The column labelled ‘Annual average’ is the result in the column labelled ‘Total cumulative’ divided by 40 years (the length of the simulation period). 

 

Table 1 cobenefits

Table 1. Summary of findings on PM-related mortality with and without consideration of GDP change, given for the baseline of no policy (0), policy Scenario 1, policy Scenario 2, policy Scenario 3, the difference between policy Scenario 1 and the baseline (0-1), the difference between policy Scenario 2 and the baseline (0-2) and the difference between policy Scenario 3 and the baseline (0-3). The final column is the fractional difference in each result with GDP included compared against the same result without GDP effects.

 

Conclusions

With respect to the central research question as to whether inclusion of economic growth in co-benefits calculations makes a significant difference in the results of those calculations, the findings here are mixed, as can be seen in Table 1. Under all four scenarios, there is a decrease in both the cumulative and average annual mortality induced by PM2.5 exposures as a result of increasing per capita GDP over the simulation period (2010 to 2050), as seen in the first four rows of Table 1. This decrease is approximately 13%, 12%, 13% and 11% for scenarios 0 (baseline), 1, 2 and 3, respectively. Similar percentage reductions are noted for annual average mortality rate (excess deaths per year due to PM2.5 exposures).

The pattern for co-benefits given by the final three rows of Table 1, is similar. For policy Scenario 1 without consideration of per capita GDP growth, the co-benefit relative to the baseline (Scenario 0) is a reduction of 26.4 million PM2.5 related deaths between 2010 and 2050, and an average annual reduction of 661,000 deaths per year. When per capita GDP growth is included, these co-benefits decline to 22.1 million PM2.5 related deaths between 2010 and 2050 (a 17% decrease relative to the case where per capita GDP growth is not included), and to 552,000 annual deaths per year (a 17% decrease relative to the case where per capita GDP growth is not included).

For policy Scenario 2 without consideration of per capita GDP growth, the co-benefit relative to the baseline (Scenario 0) is a reduction of 21.4 million PM2.5 related deaths between 2010 and 2050, and an average annual reduction of 53,600 deaths per year. When per capita GDP growth is included, these co-benefits decline to 19.1 million PM2.5 related deaths between 2010 and 2050 (a 12% decrease relative to the case where per capita GDP growth is not included), and to 47,700 annual deaths per year (a 12% decrease relative to the case where per capita GDP growth is not included).

For policy Scenario 3 without consideration of per capita GDP growth, the co-benefit relative to the baseline (Scenario 0) is a reduction of 38.6 million PM2.5 related deaths between 2010 and 2050, and an average annual reduction of 966,000 deaths per year. When per capita GDP growth is included, these co-benefits decline to 32.2 million PM2.5 related deaths between 2010 and 2050 (a 17% decrease relative to the case where per capita GDP growth is not included), and to 806,000 annual deaths per year (a 17% decrease relative to the case where per capita GDP growth is not included).

Note that the impact of per capita GDP growth on co-benefits is higher for policy Scenarios 1 and 3 than policy Scenario 2. This occurs because the influence of per capita GDP growth is significantly larger in the non-Annex I than the Annex I nations for the more stringent policies, both because of generally higher background PM concentrations and larger increases in GDP growth in the former. Hence, global policies that allow for slower rates of decarbonisation in the non-Annex I nations reduce the PM-related co-benefits of climate policies.

The overall conclusion is that estimates of co-benefits from PM emissions reductions accompanying CO2 emissions reductions are reduced by between 12% and 17% when projected increases in per capita GDP are included in calculations, with that percentage reduction increasing in the cases where more rapid and stringent GHG reductions occur in the non-Annex I nations. These changes indicate that allowing for continuing increases in per capita GDP while designing global climate policies can have a significant health benefit by itself, not necessarily in relative terms but in absolute terms. The present paper does however not explore the issue of the cost effectiveness of reducing PM emissions as a co-benefit of climate policy, in contrast to direct reductions in PM emissions by other environmental policy options.

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A key area of research at 4CMR over the past 5 years has been the development of the Future Technology Transformation model, used in exploring how policies influence global technology and carbon. This includes an on-line visualisation tool so you can view our results.

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4CMR works closely with the Cambridge Centre for Environment, Energy and Natural Resource Governance, with overlapping interests, skills and projects. C-EENRG is also located in the Department of Land Economy, with a core mission to "conduct integrative research on the governance of environmental transitions, understood as social and technological processes driven by environmental constraints that lead to fundamental changes in social organisation."

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