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What Does the World Health Organization Study of Global Health Risks Imply about Global Warming's Health Risks?

Reference
[GHR] World Health Organization. (2009). Global Health Risks, available at http://www.who.int/healthinfo/global_burden_disease/global_health_risks/en/index.html, visited on 8 May 2011.
Introduction
The World Health Organization published results from its Global Burden of Disease study for 2000 in its 2002 World Health Report (WHO, 2002). It attributed 154,000-166,000 deaths worldwide and 5.5 million lost Disability-Adjusted Life Years (DALYs) in 2000 to global warming. The methodology, however, used to develop these estimates is suspect because, as admitted by its authors:

"Empirical observation of the health consequences of long-term climate change, followed by formulation, testing and then modification of hypotheses would ... require long time-series (probably several decades) of careful monitoring. While this process may accord with the canons of empirical science, it would not provide the timely information needed to inform current policy decisions on GHG emission abatement, so as to offset possible health consequences in the future" [Emphasis added] [McMichael et al., 2004, p. 1546].

Nevertheless, these numbers have gained wide currency. They were echoed in the Intergovernmental Panel on Climate Change's latest assessment (IPCC, 2007), and major review papers in highly-regarded peer-reviewed journals such as Nature (Patz et al., 2005), Lancet (McMichael et al., 2006), Environmental Health Perspectives (Campbell-Lendrum and Woodruff, 2006), and the UCL-Lancet Commission report (Costello et al., 2009a).

On the strength of these numbers, as well as prognostications about the future impacts of climate change, some have declared that global warming is among the most important threats to public health. Costello et al. (2009a) went so far as to claim that it is the "biggest global health threat" of the 21st century.

In an exchange in the Lancet, Goklany (2009a) pointed out that the Commission had failed to provide a comparative analysis of the different health threats to support its claim that global warming, in fact, outranks all others. He then provided precisely such an analysis, also based on the 2002 World Health Report. That analysis, later expanded into a longer paper (Goklany 2009b), showed that with respect to the present, at least 20 other health risks outranked global warming currently.

Regarding the foreseeable future (defined as 2085), using results from the British government sponsored Fast Track Assessments (FTAs) of the global impact of warming (Arnell et al., 2002; Parry, 2004) and WHO mortality data, he estimated that the contribution of global warming to cumulative mortality from various health risks would, even under the warmest IPCC scenario, be 13%.

Thus, he concluded, global warming is unlikely to be now, or in the foreseeable future, the world's most important health threat. In response to Goklany (2009a), on behalf of the Commission, Costello et al. (2009b) argued that the former had used old studies-although the Commission itself had relied on the results of the very same studies.

Subsequently, the WHO published Global Health Risks (henceforth, GHR) as part of its Global Burden of Disease study for 2004 which provided new estimates of death and disease for 24 risk factors (for 2004), including global warming. GHR attributed 141,000 deaths and 5.4 million lost DALYs in 2004 to global warming.

Because GHR updates the results of WHO (2002), the earlier conclusion that global warming is outranked today by other health risks needs to be reexamined.

So what does GHR tell us about the relative importance of global warming, and what are its policy implications?

Goklany (2011) touches on answers to these questions. The following is drawn from that paper.

Current Ranking of Global Warming as a Health Risk
According to GHR, global warming will exacerbate death and disease from diarrhea, malaria, undernutrition, and 34 other associated causes (see Table 1). But none of these 37 factors are new to mankind. In fact, each has been virtually eliminated in the industrialized world. Today they are associated with poverty and its outcome, poor health services. Thus, global warming does not create new health problems as much as it makes existing, poverty related health problems worse.


Table 1: Deaths and lost DALYs attributed to global warming by disease or injury outcomes for the year 2004.
Source: WHO, Global Health Risks (2009).

Note that neither stroke nor cardiovascular disease is listed in Table 1. However, more people die in winter than in summer in many parts of the world. This phenomenon, known as "excess winter mortality," is in large part due to the seasonal increases in deaths from these two conditions during the colder months (see, e.g., Woodhouse, 1993; Keatinge, 2002). Thus, GHR apparently does not account for any reduction in mortality from higher temperatures during winter.

The GHR's estimates of death and disease attributable to global warming amount to 0.2% of all deaths and 0.4% of the burden of disease (in 2004). Not surprisingly, Figure 1, also based on GHR shows that global warming ranks second-last based on global mortality (left hand panel) or last based on the global burden of disease, i.e., lost DALYs (right hand panel). The rankings are unchanged if one focuses only on developing countries. If one considers only industrialized countries, global warming would be ranked 23rd based on mortality and 21st based on the burden of disease.


Figure 1: Ranking global public health priorities based on mortality (right hand panel) and disability-adjusted life years (DALYs) lost prematurely (left hand panel) in 2004 for 24 health risk factors. The total length of each bar indicates the magnitude of deaths or lost DALYs globally to the specific health risk factor. For developing countries, the ranking of global warming is unchanged, whereas for industrialized countries, it would rank second last on the basis of deaths, and 4th last on the basis of lost DALYs. Source: Goklany (2011), based on GHR (WHO, 2009).

Thus, regardless of the criterion, based on its current health impact, global warming does not rank high as a global public health risk.

Moreover, since GHR did not address the future impact of warming, its results do not affect the previous conclusion that through the foreseeable future the contribution of global warming to mortality from hunger, malaria and extreme weather events will continue to be small (Goklany, 2009b).

Comparing Global Warming to Poverty as a Public Health Risk
Table 2 shows the 24 risk factors arranged in descending order of the sensitivity of the disease burden to poverty. The higher it is listed on this table, the more sensitive it is to poverty, that is, the greater its relative toll in poorer countries. Sensitivity is determined using the ratio of the disease burden per capita for low-income countries to that of lower-middle-income countries (right-most column) (Goklany, 2011).


Table 2: Poverty-related Health Risks Arranged in Order of Sensitivity to Poverty. These are identified based on the ratio of disease burden rates for lower income and lower middle income groups. The grey shaded rows indicate risk factors for which the ratio for disease burden rates exceeds 2. Source: Goklany (2011) based on WHO, Global Health Risks (2009).

These ratios range from 11.9 to 0.6, with global warming having the highest ratio. This is consistent with the previous finding that global warming exacerbates diseases of poverty. In fact, of the 141,300 global deaths in 2004 attributed to warming, about 100 (0.08%) were in the industrialized countries. Similarly, with respect to the burden of disease, only 3,000 (0.06%) of the 5.4 million lost DALYs were in industrialized countries.

Ten risk factors have relative disease burden ratios exceeding 2. 99.4% of the death and disease attributed to these ten risk factors were in developing countries. That is, these risk factors are poverty-related.

In addition to global warming, these risk factors are: underweight (largely synonymous with chronic hunger); zinc deficiency; Vitamin A deficiency; unsafe sex; unsafe water, sanitation and hygiene; unmet contraceptive needs; indoor smoke from solid fuels; sub-optimal breast feeding; and iron deficiency. As Figure 1 indicates, three of these listed-underweight; unsafe sex; and unsafe water, sanitation and hygiene-are the top three health risk factors for developing countries based on their contribution to the burden of disease.

Cumulatively, GHR attributed 11.2 million deaths and 379 million lost DALYs to these nine poverty related risk factors. By contrast, 0.14 million deaths and 5.4 million lost DALYs were attributed worldwide to global warming (see Figure 1). Obviously, at present, the health consequences of global warming are trivial relative to the cumulative non-global warming impact of hunger and poverty. Under either criterion, poverty-related health risks easily outrank global warming as global priorities.

The 70- to 80--fold mismatch in scale between the diseases of poverty and global warming indicates that even a small increase in poverty due to, for example, either lower economic growth induced by efforts to reduce greenhouse gas emissions or an increase in biofuel production, could outweigh the public health benefits from the associated greenhouse gas reductions (Tol and Dowlatabadi, 2001; Tol and Yohe, 2006; Goklany, 2007, 2009c, 2011).

In fact, the improvements in public health since the start of the Industrial Revolution are in large measure due directly or indirectly to economic growth, which has been underpinned, in large part, by fossil fuel energy usage in all-agricultural, manufacturing, transportation, service, and residential-sectors (Goklany, 2007, 2010). This is illustrated in Figure 2, which indicates that as carbon dioxide emissions and economic growth began to take off in the late 18th century, life expectancy, which had been static for millennia, started to increase more or less continuously (Goklany, 2007, 2010). The long term increase in life expectancy can also be viewed as a result of continual reductions in poverty due to economic growth, and its consequences for public health.


Figure 2: Global Carbon Dioxide Emissions from Fossil Fuels, GDP per Capita, and Life Expectancy, 1760-2009. Sources: Boden et al. (2010), CDIAC (2011), Maddison (2003, 2010), World Bank (2011).

Policy Implications of GHR Results
If the 37 poverty related diseases listed on Table 1 are addressed, that would effectively reduce global warming related health problems. Industrialized countries have effectively accomplished this, which explains their minor share of death and disease attributable to global warming. So greater economic development, which is the most effective method of reducing poverty, would reduce, if not forestall, global warming related health problems.

The corollary to this is that global warming related policies that would reduce economic development or otherwise add to poverty could be counterproductive, particularly if these policies slow economic development and increase poverty in the near term, while the positive effects, if any, of emission reductions are delayed, as seems almost certain given the inertia of the climate system.

Additional References
Arnell, N.W., Cannell, M.G.R., Hulme, M., Kovats, R.S., Mitchell. J.F.B., Nicholls. R.J., Parry, M.L., Livermore, M.T.J., and White, A. (2002). The consequences of CO2 stabilization for the impacts of climate change. Climatic Change 53: 413-46.

Boden, T.A., Marland, G., and Andres, R.J. (2010). Global, Regional, and National Fossil-Fuel CO2 Emissions. Available at http://cdiac.esd.ornl.gov/trends/emis/overview_2006.html. Accessed May 11, 2011.

CDIAC. Preliminary 2008-09 Global & National Estimates by Extrapolation, CDIAC, at http://cdiac.ornl.gov/ftp/trends/co2_emis/Preliminary_CO2_emissions_2009.xls, visited 11 May 2011.

Campbell-Lendrum, D., and Woodruff, R. (2006). Comparative Risk Assessment of the Burden of Disease from Climate Change. Enviromental Health Perspectives 114: 1935-1941. doi:10.1289/ehp.8432.

Costello, A., and University College London-Institute for Global Health and Lancet Commission. 2009a. Managing the health effects of climate change. Lancet 373: 1693-1733.

Costello, A., Maslin, M., and Montgomery, H. (2009b). Response: Climate change is not the biggest global health threat. Lancet 374: 973-975.

[GHR] World Health Organization. (2009). Global Health Risks, available at http://www.who.int/healthinfo/global_burden_disease/global_health_risks/en/index.html, visited on 8 May 2011.

Goklany, I.M. (2007). The Improving State of the World. Washington, DC: Cato Institute.

Goklany, I.M. (2009a). Letter: Climate change is not the biggest global health threat. Lancet 374: 973-975.

Goklany, I.M. (2009b). Global public health: global warming in perspective. Journal of American Physicians and Surgeons 14 (3): 69-75.

Goklany, I.M. (2009c). Have increases in population, affluence and technology worsened human and environmental well-being? Electronic Journal of Sustainable Development 1(3). Available: http://www.ejsd.org/docs/HAVE_INCREASES_IN_POPULATION_AFFLUENCE_AND_TECHNOLOGY_WORSENED_HUMAN_AND_ENVIRONMENTAL_WELL-BEING.pdf.

Goklany, I.M. (2010). Drivers of Ecosystem Service Changes Can Go Both Ways: Economic Development, Technology and Population. ACES: A Community on Ecosystem Services, Conference, December 6-9, 2010, Gila River Indian Community, Phoenix, Arizona.

Goklany, I.M. (2011). Could Biofuel Policies Increase Death and Disease in Developing Countries? Journal of American Physicians and Surgeons 16 (1): 9-13.

Keatinge, W.R. (2002). Winter Mortality and its Causes. International Journal of Circumpolar Health 61: 292-99.

Maddison A. (2003). Historical Statistics for the World Economy: 1-2003 AD. Available at http://www.ggdc.net/maddison/, visited 12 July 2008.

Maddison A.(2010). Statistics on World Population, GDP and Per Capita GDP, 1-2008 AD. Available at http://www.ggdc.net/MADDISON/Historical_Statistics/horizontal-file_02-2010.xls. Accessed 11 May 2011.

McMichael, A.J., Campbell-Lendrum, D., Kovats, S., et al. (2004). Global Climate Change. In Comparative Quantification of Health Risks: Global and Regional Burden of Disease due to Selected Major Risk Factors. Geneva: World Health Organization, pp.1543-1649.

McMichael. A.J., Woodruff, R.F., and Hales, S. (2006). Climate change and human health: present and future risks. Lancet 367: 859-869.

Parry, M.L., ed. (2004). Special issue: an assessment of the global effects of climate change under SRES emissions and socio-economic scenarios. Global Environmental Change 14: 1-99.

Patz, J.A., Campbell-Lendrum, D., Holloway, T., and Foley, J.A. (2005). Impact of regional climate change on human health. Nature 438: 310-17.

Tol, R.S.J., and Dowlatabadi, H. (2001). Vector-borne diseases, development & climate change. Integrated Assessment 2: 173-181.

Tol, R.S.J., and Yohe, G.W. (2006). Of Dangerous Climate Change and Dangerous Emission Reduction. In Schellnhuber, H.J., Cramer, W, Nakicenovic, N., et al. Avoiding Dangerous Climate Change. Cambridge: Cambridge University Press, pp. 291-298.

Woodhouse, P.R. (1993). Why Do More Old People Die In Winter? Journal of the Hong Kong Geriatric Society 3: 23-29.

World Bank. (2011) World Development Indicators, available at http://databank.worldbank.org/ddp/home.do, visited 8 May 2011.

WHO. (2002). World health report 2002 statistical annex. Geneva: WHO, 2002. Accessed May 15, 2010 at http://www.who.int/whr/2002/annex/en/index.html

Archived 24 May 2011