“Those who envisage a
fundamental link between the thermodynamic arrow of energy dissipation
and the biological arrow of the greening earth make up a small
minority, and stand well outside the main stream of contemporary
biological science. But if their vision is true, it reveals that
deep continuity between physics and biology, the ultimate wellspring
of life.”
Franklin M. Harold
Ecosystems display a direction, an increase in gradient
reduction over time. The more mature an ecosystem, the more solar energy
it degrades. This is not a theory, but a fact: ecological richness
correlates with temperature gradient reduction. Rain forests are cooler
than grassland steppes or deserts. Unlike forays into the nature of
complex systems that trumpet a potential likeness between computer-generated
designs and growth patterns in nature, the thermodynamic view relates
energy degradation directly to living complexity. The data are tight.
The energy basis of complex cycling systems is not just a theoretical
possibility. It organizes the real world.
Luvall has also measured urban areas. Flying over
a city, he looked at the radiation from parks, parking lots, and lawns.
Much of the city reradiated large amounts of sensible infrared heat
from its black roofs and streets. Solar energy is absorbed and reradiated
as heat, causing surface temperatures of low-albedo surfaces like roads
and black roofs to become 50–70°F warmer than the ambient air. Any roofer can
tell you how to keep your home cooler: paint your roof white or silver
and the radiation hitting it is reradiated back into space, as if off
a mirror, with very little of the incoming solar energy converted into
sensible heat. Now NASA has Luvall measuring the temperatures of cities
such as Atlanta. It turns out that, just by painting roofs silver or
white, cities could save billions in air-conditioning costs. In the meantime
cities like Atlanta generate large heat islands with temperatures over
the city that are 7°F above ambient rural temperatures . These heat
islands can generate their own climate, with thunderstorms emerging from
the convective upwelling of warmer city air.
Remote sensing and painting roofs silver are a kind of
applied human ecology. Human populations expand and dramatically change
planetary energy budgets. What is good for rapidly growing human populations
is not necessarily good for larger ecosystems. Nietzsche said the world
is beautiful, but has a pox called man. Thermodynamically, this is true
insofar as our global activities have impaired life's most highly developed
systems of gradient breakdown. Despite occasional short-term cold spells,
the long-term climate is definitely trending warmer. To date, 2003 was
the second warmest year on record (since 1880); the five warmest years
on record have all occurred since 1997, and the ten warmest years, globally
averaged, appeared between 1990 and 2003. Such heat, traceable to fossil-fuel
emissions and perhaps clear-cutting, which lowers forests' transpiration
abilities (and thus their ability to reflect heat via clouds into space),
represent decreased global gradient reduction. The hope is that our rapid
growth, the first of its kind in Earth's history, will settle down as
we integrate our technologies with the rest of life, enhancing rather
than curtailing the cooling powers of rain forests and other highly evolved
ecosystems.
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Part
III: The living
11.
Thermodynamics and Life
12.
Brimstone Beginnings
13.
Blue Planet Blues
14.
Regress under Stress
15.
The Secret of Trees
16.
Into the Cool
17.
Trends in Evolution
There is a giant radiation gradient between the 5,800 K temperature of the sun's
surface and the 2.7 K Hawking temperature of outer space. The Earth is suspended
in this gradient, and disequilibrium processes such as chemical associations,
weather, and life can and do occur because of the access to this high-energy
flux.
Mean outgoing long-wave radiation (OLR) in watts per square
meter, collected by satellite showing the global reradiation into space. This
reradiation is proportional to the temperature of the surface of the Earth below
the satellite. Disregarding the oceans and focusing on the landmasses, it is
evident that the desert regions are hot and the regions of the large rain forests,
Amazon, Congo, Indonesia, New Guinea, Borneo, and so on, appear cold. The cold
temperatures over the rain forests are not always the temperatures of the land
and plant surfaces but are the temperature of the high clouds. The clouds result
from transpiration from the rain forest below. The forest and clouds are a coupled
system cooling the Earth. Clear sky (cloudless) measurements of the Earth show
the same pattern of hot deserts and cold rain forests. (Courtesy of the Climate
Analysis Center of the National Oceanic and Atmospheric Administration.)
Measurements of reradiated surface temperatures over Atlanta, Georgia. Luvall
used an airplane equipped with a highly accurate radiometer and measured surface
temperature of the city and the surrounding landscapes. The temperature over
the city was 7°F warmer than the surrounding countryside. The warmer city
surface temperatures are a result of sensible heat production from creosoted
roofs and blacktop roads that have replaced cooling transpiring trees. Even small
parks cooled the suburbs. The warm air over Atlanta rises via convection and
causes thunderstorms downwind from the city. (Adapted from Taha, Akbari, and
Sailor 1992.)
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