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Comments on "Anthropogenic Heat Release: Estimation
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of Global Distribution and Possible Climate Effect" by
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Chen B. et al.
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Fumiaki FUJIBE1
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Meteorological Research Institute, Tsukuba, Japan
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(Present affiliation: Tokyo Metropolitan University, Hachioji, Japan)
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May 8, 2015
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-----------------------------------1) Corresponding author: Fumiaki Fujibe, Faculty of Urban Environmental Sciences, Tokyo
Metropolitan University, 1-1 Minami-Osawa, Hachioji 192-0397, JAPAN.
E-mail: [email protected].
Tel: +81-42-677-2593
Fax: +81-42-677-2589
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Abstract
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Chen et al. (2014) estimated the global distribution of anthropogenic heat release
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(AHR) using satellite observed night lights, and showed a rapid increase of AHR from
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2000 to 2009 in many regions including Europe and North America. From model
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simulation based on this estimation, they showed a possibility of substantial influence of
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AHR on the climate over some regions of the world. However, existing data indicate that
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neither energy consumption nor night lights changed largely from 2000 to 2009. These
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facts raise serious doubts about the reliability of their results.
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Keywords: anthropogenic heat release, climate change, night light data
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1. Introduction
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Chen et al. (2014; hereafter C14) estimated the global distribution of anthropogenic heat
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release (AHR) for 1992, 2000, and 2009 using night light data of Defense Meteorological
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Satellite Program (DMSP)/Operational Linescan System (OLS). Their result indicates that
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AHR in 2009 was considerably larger than in 2000, possibly by an order of magnitude
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according to their Figs.2 and 3, reaching an annual mean value of 20Wm-2 in concentrated
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regions in Europe, North America and East Asia. Using this estimation and a numerical
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model, they concluded that "AHR has a significant impact on surface temperature and that
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it is able to affect global atmospheric circulation, leading to a 1-2 K increase in the
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high-latitude areas of Eurasia and North America".
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It is believed that AHR can reach 100Wm-2 in the central area of large cities, and has
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some effects on urban temperature (e.g., Aoyagi et al. 2012). However, area of large AHR
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is limited, so that contribution of anthropogenic heat to large-scale temperature fields is
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believed to be negligible, apart from some regions where changes in atmospheric
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circulation may cause perceivable temperature increase (Zhang et al. 2013). In this respect,
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the study of C14 may be regarded as presenting a new aspect of the science of global
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climate. However, there is serious doubt about the validity of their results, as discussed in
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the following.
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2. Problems in the AHR estimation by C14
Figure 1 shows the trend of energy consumption in the world and regions provided by the
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Agency
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(http://www.enecho.meti.go.jp/about/whitepaper/2014html/2-2-1.html). There is a marked
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increase in the Asia-Oceania region, which has a number of rapidly developing countries
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such as China and India, whereas Europe and North America show little change after 2000.
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In fact, energy consumption in 2009 was of the same amount as that in 2000 in Europe,
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and 2% smaller than in 2000 in North America. For Japan, the energy consumption in 2009
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was
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(http://www.enecho.meti.go.jp/about/whitepaper/2014html/2-1-1.html).
for
8%
Natural
smaller
Resources
than
and
Energy
that
of
in
Japan
2000
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Data of DMSP/OLS night light can be obtained from NOAA's National Geophysical Data
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Center (NGDC). The file of "National trends with intercalibrated DMSP stable light"
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(http://ngdc.noaa.gov/eog/dmsp/download_national_trend.html) provides annual records of
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"Sum of Lights (SOL)" in each country since 1992, including "mean SOL" that is an average
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of SOL from satellites available. Figure 2 shows the trends of mean SOL per unit area for
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some counties in Europe and East Asia, and USA. It can be seen that SOL does not show a
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remarkable increase except in China and India. Figure 3 shows the relationship of SOL in
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2000 and 2009 for each country. The ratio of SOL in 2009 to that in 2000 is 1.79 in China
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and 1.29 in India, but is less than 1.1 for other countries except Spain (1.14). In fact, the
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ratio is less than 1 in USA (0.84), UK (0.87), and Japan (0.93).
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Fig. 1
Fig. 2
Fig. 3
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Thus both energy consumption and intensity of night lights are found to have changed
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little from 2000 to 2009 in European countries and USA, and also in Japan. Since C14's
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estimation of AHR is based on a linear regression of light intensity and anthropogenic heat
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flux (Fig.1 of Chen and Shi (2012)), AHR should be estimated to be constant as long as
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SOL is unchanged. We can therefore conclude that the rapid increase of AHR described by
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C14 is unreliable, and so is their model results based on this estimation as to the influence
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of AHR on the global climate.
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3. Supplementary remarks
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Flanner (2009) estimated the global distribution of AHR using energy consumption data.
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His result for 2005 indicates that "regionally-averaged heat fluxes are sufficiently large (≈1
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Wm-2)" in western Europe and eastern USA (his Fig.1). In comparison, the values of AHR
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shown in C14 for 2009 appear to be much larger, seemingly by an order of magnitude
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according to the coloring of their Fig.3. In other words, the results of Flanner (2009) and
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C14 are incompatible, apart from the difference of four years.
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Bennie et al. (2014) analyzed the changes of night light brightness in Europe for 1995 to
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2010 using the DMSP/OLS data. They showed that "the continental trend is towards
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increasing brightness", but the rate of increase is not so large (seemingly of the order of
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10%), while "some economically developed regions show more complex patterns with large
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areas decreasing in observed brightness". The slight increase of brightness in their analysis
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agrees with the increase of SOL in some countries in Figs. 2 and 3, such as Spain, Italy,
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and France.
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The results of these studies are consistent with our conclusion that C14's estimation of
AHR in 2009 is unrealistically large.
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Acknowledgments
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The author is grateful to Mr. Takashi Yamada and Mr. Yoshinori Oikawa, JMA, for
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valuable discussion.
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References
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Aoyagi, T., N. Kayaba, and N. Seino, 2012: Numerical simulation of the surface air
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temperature change caused by increases of urban area, anthropogenic heat, and
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building aspect ratio in the Kanto-Koshin area. J. Meteor. Soc. Japan, 90B, 11-31.
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Bennie, J., T. W. Davies, J. P. Duffy, R. Inger, and K. J. Gaston, 2014: Contrasting trends in
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light pollution across Europe based on satellite observed night time lights. Sci. Rep., 4,
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3789, doi:10.1038/srep03789.
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Chen, B., and G.-Y. Shi, 2012: Estimation of the distribution of global anthropogenic heat
flux. Atmos. Oceanic. Sci. Lett., 5, 108-112.
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Chen, B., L. Dong, G.-Y. Shi, L.-J. Li, and L.-F. Chen, 2014: Anthropogenic heat release:
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Estimation of global distribution and possible climate effect. J. Meteor. Soc. Japan, 92A,
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157-165.
Flanner, M. G., 2009: Integrating anthropogenic heat flux with global climate models.
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Zhang, G. J., M. Cai, and A. Hu, 2013: Energy consumption and the unexplained winter
warming over northern Asia and North America. Nat. Clim. Change, 3, 466-470.
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List of Figures
Fig.1
Annual energy consumption in the world and regions.
Fig.2
Trends of "mean SOL (sum of lights)" per unit area for each country.
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Fig.3 Comparison of mean SOL in 2000 and 2009 for each country. The dashed line is the
y=x line.
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Energy consumption (109 toe)
Asia and
Oceania
Africa
Middle East
Former USSR
Europe
C&S America
North America
Fig.1 Annual energy consumption in the world and regions.
SOL (km-2)
S. Korea
Italy
Germany
UK
Japan
France
Spain
USA
India
China
Fig.2 Trends of "mean SOL (sum of lights)" per unit area for each country.
SOL in 2009 (km-2)
S. Korea
Germany
Italy
UK
France
Japan
Spain
India
USA
China
SOL in 2000 (km-2)
Fig.3 Comparison of mean SOL in 2000 and 2009 for each
country. The dashed line is the y=x line.