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
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
.
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 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 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.
http://www.knmi.nl/~laatdej/EOS2008.pdf
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