Science Briefs
Coal and Gas are Far More Harmful than Nuclear Power
By Pushker Kharecha and James Hansen — April 2013
Human-caused climate change and air pollution remain major
global-scale problems and are both due mostly to fossil fuel burning.
Mitigation efforts for both of these problems should be undertaken
concurrently in order to maximize effectiveness. Such efforts can be
accomplished largely with currently available low-carbon and carbon-free
alternative energy sources like nuclear power and renewables, as well
as energy efficiency improvements.
Figure 1.
Cumulative net deaths prevented assuming nuclear power replaces fossil
fuels. The top panel (a) shows results for the historical period in our
study (1971-2009), with mean values (labeled) and ranges for the
baseline historical scenario. The middle (b) and bottom (c) panels show
results for the high-end and low-end projections, respectively, of
nuclear power supply estimated by the IAEA (ref. 4) for the period
2010-2050. Error bars reflect the ranges for the fossil fuel mortality
factors listed in Table 1 of our paper. The larger columns in panels (b)
and (c) reflect the all-coal case and are labeled with their mean
values, while the smaller columns reflect the all-gas case; values for
the latter are not shown because they are all simply a factor of about
10 lower (reflecting the order-of-magnitude difference between the
mortality factors for coal and gas). Countries/regions are arranged in
descending order of CO2 emissions in recent years. FSU15=15
countries of the Former Soviet Union and OECD=Organization for Economic
Cooperation and Development.
In a recently published paper (ref. 1), we provide an objective,
long-term, quantitative analysis of the effects of nuclear power on
human health (mortality) and the environment (climate). Several previous
scientific papers have quantified global-scale greenhouse gas (GHG)
emissions avoided by nuclear power, but to our knowledge, ours is the
first to quantify avoided human deaths as well as avoided GHG emissions
on global, regional, and national scales.
The paper demonstrates that without nuclear power, it will be even
harder to mitigate human-caused climate change and air pollution. This
is fundamentally because historical energy production data reveal that
if nuclear power never existed, the energy it supplied almost certainly
would have been supplied by fossil fuels instead (overwhelmingly coal),
which cause much higher air pollution-related mortality and GHG
emissions per unit energy produced (ref. 2).
Using historical electricity production data and mortality and
emission factors from the peer-reviewed scientific literature, we found
that despite the three major nuclear accidents the world has
experienced, nuclear power prevented an average of over 1.8 million net
deaths worldwide between 1971-2009 (see Fig. 1). This amounts to at
least hundreds and more likely thousands of times more deaths than it
caused. An average of 76,000 deaths per year were avoided annually
between 2000-2009 (see Fig. 2), with a range of 19,000-300,000 per year.
Figure 2.
Mean net deaths prevented annually by nuclear power between 1971-2009
for various countries/regions. Ranges not shown but are a factor of ~4
higher and lower than the mean values.
Likewise, we calculated that nuclear power prevented an average of 64 gigatonnes of CO
2-equivalent (GtCO
2-eq)
net GHG emissions globally between 1971-2009 (see Fig. 3). This is
about 15 times more emissions than it caused. It is equivalent to the
past 35 years of CO
2 emissions from coal burning in the U.S.
or 17 years in China (ref. 3) — i.e., historical nuclear energy
production has prevented the building of hundreds of large coal-fired
power plants.
To compute potential future effects, we started with the projected
nuclear energy supply for 2010-2050 from an assessment made by the UN
International Atomic Energy Agency that takes into account the effects
of the Fukushima accident (ref. 4). We assume that the projected nuclear
energy is canceled and replaced entirely by energy from either coal or
natural gas. We calculate that this nuclear phaseout scenario leads to
an average of 420,000-7 million deaths and 80-240 GtCO
2-eq
emissions globally (the high-end values reflect the all coal case; see
Figs. 1 and 3). This emissions range corresponds to 16-48% of the
"allowable" cumulative CO
2 emissions between 2012-2050 if the world chooses to aim for a target atmospheric CO
2
concentration of 350 ppm by around the end of this century (ref. 5). In
other words, projected nuclear power could reduce the CO
2 mitigation burden for meeting this target by as much as 16-48%.
The largest uncertainties and limitations of our analysis stem from
the assumed values for impacts per unit electric energy produced.
However, we emphasize that our results for both prevented mortality and
prevented GHG emissions could be substantial underestimates. This is
because (among other reasons) our mortality and emission factors are
based on analysis of Europe and the US (respectively), and thus neglect
the fact that fatal air pollution and GHG emissions from power plants in
developing countries are on average substantially higher per unit
energy produced than in developed countries.
Figure 3.
Cumulative net GHG emissions prevented assuming nuclear power replaces
fossil fuels. The three panels are ordered the same as in Fig. 1, except
that mean values for both the all coal and all gas cases are labeled.
Error bars reflect the ranges for the fossil fuel emission factors
listed in Table 1 of our paper.
Our findings also have important implications for large-scale "fuel
switching" to natural gas from coal or from nuclear. Although natural
gas burning emits less fatal pollutants and GHGs than coal burning, it
is far deadlier than nuclear power, causing about 40 times more deaths
per unit electric energy produced (ref. 2).
Also, such fuel switching is practically guaranteed to worsen the
climate problem for several reasons. First, carbon capture and storage
is an immature technology and is therefore unlikely to constrain the
resulting GHG emissions in the necessary time frame. Second, electricity
infrastructure generally has a long lifetime (e.g., fossil fuel power
plants typically operate for up to ~50 years). Third, potentially usable
natural gas resources (especially unconventional ones like shale gas)
are enormous, containing many hundreds to thousands of gigatonnes of
carbon (based on ref. 6). For perspective, the atmosphere currently
contains ~830 GtC, of which ~200 GtC are from industrial-era fossil fuel
burning.
We conclude that nuclear energy — despite posing several challenges,
as do all energy sources (ref. 7) — needs to be retained and
significantly expanded in order to avoid or minimize the devastating
impacts of unabated climate change and air pollution caused by fossil
fuel burning.
References
1. Kharecha, P.A., and J.E. Hansen, 2013:
Prevented mortality and greenhouse gas emissions from historical and projected nuclear power.
Environ. Sci. Technol.,
47, 4889-4895, doi:10.1021/es3051197.
2. Markandya, A., and P. Wilkinson, 2007:
Electricity generation and health.
Lancet, 370, 979-990,
doi:10.1016/S0140-6736(07)61253-7.
3. Boden, T. A., G. Marland, R.J. Andres, 2012:
Global, Regional, and National Fossil-Fuel CO2 Emissions.
Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.,
doi:10.3334/CDIAC/00001_V2012.
4. International Atomic Energy Agency, 2011:
Energy, Electricity and Nuclear Power Estimates for the Period up to 2050: 2011 Edition.
IAEA Reference Data Series 1/31.
Available at
http://www-pub.iaea.org/MTCD/Publications/PDF/RDS1_31.pdf
5. Hansen, J., P. Kharecha, Mki. Sato, V. Masson-Delmotte, et al., 2013:
Scientific prescription to avoid dangerous climate change to protect young people, future generations, and nature.
PLOS One, submitted.
6. GEA, 2012:
Global Energy Assessment — Toward a Sustainable Future.
Cambridge University Press, Cambridge, UK and New York, NY, USA and the
International Institute for Applied Systems Analysis, Laxenburg,
Austria.
Available at http://www.globalenergyassessment.org.
7. Kharecha, P.A., C.F. Kutscher, J.E. Hansen, and E. Mazria, 2010:
Options for near-term phaseout of CO2 emissions from coal use in the United States.
Environ. Sci. Technol., 44, 4050-4062, doi:10.1021/es903884a.
Contact
Please address all inquiries about this research to
Dr. Pushker Kharecha.
http://www.giss.nasa.gov/research/briefs/kharecha_02/