An edited version of this paper was published by AGU. EOS transactions FORUM, Vol. 89, No. 51, doi: 10.1029/2008EO510005, 16 December 2008. Copyright (2008) American Geophysical Union. http://www.agu.org/journals/eo/eo0851/2008EO510005.pdf A.T.J. de Laat Royal Netherlands Meteorological Institute (KNMI) PO box 301 3730 AE De Bilt, the Netherlands
Current Climate Impact of Heating from Energy Usage A.T.J. de Laat
Present-day waste heat production as a result of energy use is a climate forcing that has not drawn much attention, although Chaisson [2008] recently discussed its potential future climate impact. Current global primary energy consumption amounts to 15.5 TeraWatts (U.S. Energy Information Administration (EIA) base year 2005; see Table 1). The global average primary energy consumption (0.03 watts per square meter) is relatively small compared to other anthropogenic radiative forcings, as summarized in the recent Intergovernmental Panel on Climate Change [2007] report. Nevertheless, despite its relatively small magnitude, waste heat may have a considerable impact on local surface temperature measurements, as outlined below Unlike the globally well-mixed greenhouse gases carbon dioxide (CO2) and methane (CH4), energy use does not occur uniformly around the globe. Assuming that energy use predominantly occurs over land (30% of the globe) and that one-third of the land is populated, energy use for this populated land area is already 0.3 watts per square meter. We can further investigate the
magnitude of energy use by calculating energy consumption per country in watts per square meter using the energy consumption estimates from EIA (table 1). For large energy consuming countries such as the United States, China, and India, the energy consumption is of the order of 0.2-0.4 watts per square meter. For smaller developed countries such as France, the United Kingdom, Germany, and Japan, energy consumption per square meter is larger, exceeding 1 watt per square meter. For small, densely populated countries such as the Netherlands, energy consumption exceeds 4 watts per square meter. On a city scale, such as central New York or Tokyo, energy use can exceed 100 watts per square meter [Makar et al., 2006]. Although these numbers are merely statistics, they clearly show that on local to regional scales the magnitude of waste heat is large. In addition, the spatial inhomogeneous distribution of the waste heat effect may actually have a much larger impact on local and regional atmospheric circulation than what could be expected based on their global average. This impact can be larger than the local to regional impact of well-mixed greenhouse gases [Matsui and Pielke, 2007]. Furthermore, the near-surface impact of waste heat will be larger in cold climates compared to warm climates and larger during nighttime compared to daytime due to a combination of differences in mixing depth (boundary layer height), latent and sensible heat balance (at low temperatures, hardly any evaporative cooling occurs), and radiative equilibrium temperature (Stefan-Boltzmann law).
Observed and modeled waste heat impact.
There is some observational evidence that waste heat has changed temperatures not only locally but also regionally. Several recent papers [de Laat and Maurellis, 2006 and references therein; McKitrick and Michaels, 2007 and references therein] suggest that a link exists between observed warming patterns and industrialization or urbanization. For example, there is considerably more surface than free tropospheric warming in the eastern United States, suggesting the presence of a surface warming process [Kalnay et al., 2006; and references therein]. Waste heat may very well have contributed to the observed temperature change patterns, although it is unclear as to whether waste heat can fully account for these patterns. There are more anthropogenic surface processes that may have contributed, such as decreases of anthropogenic (industrial) aerosols, which would also result in warming. Furthermore, waste heat also can have effects on temperatures beyond large urbanized areas. Hinkel and Nelson [2007; and references therein] have convincingly shown that for the remote location of Barrow, Alaska, local in-town temperature changes are directly related to gas use (heating). Further away from town, changes in temperature are considerably smaller, while in general the temperature changes were also dependent on local atmospheric conditions such as wind speed and atmospheric stability. Finally, Block et al. [2004] used a regional climate model to investigate the magnitude of warming in Western Europe caused by adding 2 watts per square meter of energy at the model land surface. Although the model simulation was performed for just 3 months during spring, the results nevertheless indicate that warming does occur, and—under favorable conditions—it can on average be as large as 1°C for the 2 watts per square meter surface forcing. Furthermore, the model results indicate that low elevation areas experience more warming that elevated regions,
suggesting that local atmospheric stability conditions and boundary layer dynamics are important for the magnitude of local temperature changes caused by waste heat.
Consequences for surface temperature observations.
Because waste heat is a process that also occurs on small spatial scales, the question as to the extent to which surface temperature observations have been affected by waste heat and how to account for it is very relevant. Waste heat is often associated with urbanization, but may have affected temperatures at locations that are not considered to be urban at all. Thus, when does waste heat change temperature measurements by tenths of a degree Kelvin or more? A big city at a 100 kilometer distance away from an observation site, a small city at 10 kilometers, a town 1 kilometer away, a large building 100 meters away? Surface temperature observations generally are made in the vicinity of at least some human activity, as indicated by the photographic survey of surface stations on the Web site http://www.surfacestations.org/. Common practice is to correct for urbanization effects by excluding or correcting observations close to large urbanized areas, for example by using satellite-observed city lights to identify surface observation locations close to or in large urbanized areas [Hansen et al., 2001; Peterson, 2003]. However, it is unclear what the magnitude and footprint of a waste heat source has to be in order for it to affect local and regional temperatures, and whether satellite-observed city lights can be used to account for such small-scale processes (i.e. 10 kilometer to meter scale). To answer these questions requires a detailed analysis of all available surface station data, which unfortunately appears to be a monumental task. Not only would it involve analyzing
thousands of station records in detail, but every location would have to be investigated—for its proximity to waste heat sources, the type of waste heat sources, and the historical changes of those sources (which may not be available when going further back in time)—as well as local and regional weather and climate variations, in order to estimate the footprint of the waste heat source. Regional climate models and large eddy models may further assist in estimating the footprint of regional local scale energy use. Such analyses would help to narrow down uncertainties associated with estimating the current—and future—impact of waste heat.
References
Chaisson, E. J., Long-term global heating from energy usage, EOS, 89, pp. 253-260, 8 July 2008.
Hansen, J., R. Ruedy, M. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl, A closer look at United States and global surface temperature change, J. Geophys. Res., 106, 23,947–23,963, 2001.
Hinkel, K. M. and Nelson, F. E., Anthropogenic heat island at Barrow, Alaska, during winter: 2001-2005, J. Geophys. Res., 112, doi:10.1029/2006JD007837, 2007.
Kalnay, E., M. Cai. H. Li, and C. J. Tobin, Estimation of the impact of land-use changes and urbanization on climate trends east of the Rockies, J. Geophys. Res.,111, D06106, doi: 10.1029/2005JD006555, 2006.
de Laat A. T. J., and A. N. Maurellis, Further evidence for influence of surface processes on lower tropospheric and surface temperature trends, Int. J. Clim., 26, 897-913, 2006.
Makar, P. A., S. Gravel, V. Chirkov, K. B. Strawbridge, F. Froude, J. Arnold, and J. Brook, Anthropogenic heat flux, urban properties, and regional weather. Atmos. Environ. 40, 27502766, 2006.
Matsui, T. and R. A. Pielke Sr., Measurement-based estimation of the spatial gradient of aerosol, Geophys. Res. Lett, 33, doi:10.1029/2006GL025974, 2006.
McKitrick R. R., P. J. Michaels, Quantifying the influence of anthropogenic surface processes and inhomogeneities on gridded global climate data, J. Geophys. Res., 112, D24S09, doi:10.1029/2007JD008465, 2007.
Peterson, T. C., Assessment of urban versus rural in situ surface temperatures in the contiguous United States: no difference found. J. Clim., 16, doi:10.1175/1520-0442, 2941–2959, 2003.
Author Information
A. T. J. de Laat, Royal Netherlands Meteorological Institute (KNMI), The Netherlands; E-mail:
[email protected]
Country Netherlands Japan Germany United Kingdom France United States China India Global
Area (1010 m2) 3.4 36.5 34.9 24.4 55.0 916.2 932.7 297.3 51000.0
Energy (1015 Btu) 3.4 22.6 14.5 10.0 11.4 100.7 67.1 16.2 462.8
Energy (1018 J/y) 4.5 23.8 15.3 10.6 12.0 106.2 70.8 17.1 488.3
Energy (1011 W) 1.42 7.55 4.85 3.34 3.81 33.68 22.44 5.42 154.8
Forcing (W/m2) 4.19 2.07 1.39 1.37 0.69 0.37 0.24 0.18 0.03
Table 1. Primary energy consumption for various large energy consuming and industrialized countries. Values represent the year 2005 and are taken from the U.S. Energy Information Administration’s
Web
site
(http://www.eia.doe.gov/pub/international/iealf/tablee1.xls;
downloaded 12 July 2008). Btu stands for British thermal unit (=1055 Joules). Conversion from Joules/year (J/y) to Watts per square meter (W/m2) assumes 365 days in a year and 86,400 seconds in a day. The area coverage of countries is obtained from the United Nations Statistics Division Web site (http://unstats.un.org/unsd/default.htm; downloaded 13 July 2008), also for 2005.
