it comes to stirring up passionate feelings, romance can't hold
a candle to the ongoing saga of global warming.
Not surprisingly, the climate controversy is once
again a front-page news item, now that the new man in the White
House has nullified the preceding administration's agreement to
the 1997 Kyoto accords.
Under the pact, the United States would bear the
brunt of reducing the world's future carbon dioxide emissions (CO2)
-- a costly undertaking that is perhaps less popular today than
ever, given the somewhat spooked national economy.
Opinions vary as to whether such emissions actually
impact climate change.
There are basically two camps in the longtime, intense
global warming debate -- those who say human activity is responsible
for the earth's warming and those who decry this notion, saying
the natural systems at work are much too vast to be influenced by
Intensifying the debate are those who charge that
much of the verbal wrangling over the human contribution to global
warming often is based on emotion rather than fact.
However, since the issue catapulted to prominence
in the late 1980s, there has been a concerted effort to scientifically
and methodically evaluate what actually is happening with the world
climate -- and to what extent human beings figure in the big picture.
Pointing a Finger
The Intergovernmental Panel on Climate Change (IPCC)
has emerged as the international voice on the science of global
The IPCC is a United Nations organization with a
mandate to provide policy makers with an objective assessment of
the scientific, technical and socio-economic information available
about climate change, its environmental and socio-economic impacts
and possible response options.
"Each report by the IPCC reviews all the published
literature over the previous five years or so," said Kevin Trenberth
at the National Center for Atmospheric Research. "It assesses the
state of knowledge, while attempting to reconcile disparate claims,
resolve discrepancies and highlight uncertainties.
"The strength is that the result is a consensus report
that isn't necessarily the latest or the greatest," he said, "but
it does sort out what can be reliably stated."
The latest IPCC report (2001) reaffirms earlier conclusions
the organization reported: The world's climate is changing, and
the blame rests principally on humans who are altering the composition
of the atmosphere by deforestation and the use of fossil fuels.
The changes can be slowed but not stopped, the report
says, because of the long life of several greenhouse gases (>100
years for CO2). It purports that all the climate change
the planet is already committed to has yet to manifest itself because
of the slow response of the oceans to warming.
Furthermore, major climate changes are projected
under all likely future scenarios, with change rates much greater
than occur naturally, thereby making them very disruptive in all
Natural climate changes are an age-old, ongoing phenomenon.
For those who believe human-modification of the environment alters
the climate, the impact of fossil fuel combustion ranks pretty much
at the top of the culprit list. It's blamed for polluting the atmosphere
and altering the balance of radiation on the earth via both visible
particulate pollution (aerosols) and gases that alter the makeup
of the atmosphere.
"The latter are referred to as greenhouse gases because
they are relatively transparent to incoming solar radiation, while
they absorb and re-emit outgoing infrared radiation," Trenberth
said, "creating a blanketing effect which results in warming.
"Global warming and associated climate change are
expected as a result."
Human activities, such as biomass burning, agriculture,
fossil fuel use and others, also are blamed for the increase in
atmospheric concentration of several other greenhouse gases, e.g.
methane, nitrous oxide, chlorofluorocarbons (CFCs) and the like.
Analyses of surface temperature observations show
there has been a global mean warming of about 0.7°C over
the past 100 years. The warmest year on record was 1998, and the
last 10 years are the warmest decade.
Because of land/ocean contrasts and physical obstacles
such as mountain ranges, along with other factors, extensive regions
of both above- and below-normal temperatures occur in disparate
places at any time.
Trenberth noted that changes in climate variability
and extremes are beginning to emerge.
Radiation from the sun is the energy source that
drives the climate. Roughly 31 percent is scattered or reflected
back into space by clouds and the small airborne particles known
as aerosols, or by the earth's surface. To balance the incoming
energy, the earth has to radiate the same amount of energy back
into space on average.
Water vapor, CO2 and other minor gases
in the atmosphere absorb some of the thermal radiation leaving the
surface and emit radiation from higher and colder levels out into
space. This blanketing is the natural greenhouse effect, with water
vapor contributing about 60 percent of the effect and CO2
accounting for about 26 percent.
While clouds have a blanketing effect similar to
that of greenhouse gases, they act to cool the surface because they
are bright reflectors of solar radiation.
Trenberth said the amount of CO2
in the atmosphere has increased by about 31 percent since
the industrial revolution began 250 years ago, primarily because
of fossil fuel combustion and the removal of forests. Without controls,
future projections indicate the rate of increase could accelerate,
he added, and concentrations could double from pre-industrial values
in the next 50 to 100 years.
It's been reported that even full implementation
of the Kyoto Protocol would only slow the time of doubling of CO2
concentrations in the atmosphere from pre-industrial amounts by
maybe 15 years unless sizeable further emissions reductions were
to occur at some time in the future. Changes occurring in the oceans
Because certain aerosols scatter some solar radiation
back to space, thereby cooling the earth's surface, they directly
influence climate. As opposed to aerosols generated by natural causes,
man-made aerosol particle formation occurs mainly through sulfur
dioxide injection into the atmosphere, which contributes to acid
Whereas such aerosols originate near the surface,
for the most part, they can be washed out of the atmosphere by rain.
Because they typically stay in the atmosphere for only a few days
and tend to concentrate near their sources, such as industrial regions,
they can help to mask any global warming triggered by greenhouse
Increases in greenhouse gases in the atmosphere are
reported to not only increase surface temperatures but also to augment
the hydrological cycle because much of the heating at the surface
goes into evaporating surface moisture.
"Global temperature increases signify the water-holding
capacity of the atmosphere increases," Trenberth said, "and together
with enhanced evaporation, this means that the actual atmospheric
moisture should increase, which is observed to be happening in many
"Because water vapor is a powerful greenhouse gas,
this provides a strong positive feedback."
He noted it leads to the expectation of intensified
rainfall or snowfall events, such that when it rains it pours harder
than it would have under similar circumstances just a couple of
"This also provides fuel for storms," he said, "which
further enhances rainfall and snowfall intensity, increasing the
risk of flooding."
Precipitation in the United States has trended upwards
by about 10 percent over the last century, and increased heat for
drying means naturally-occurring droughts likely will be intensified.
They will come on quicker, plants will wilt sooner and the droughts
may become more widespread and last longer with global warming.
Once the land is dry, all the solar radiation goes into raising
temperatures, Trenberth said, bringing on sweltering heat waves.
Clearly, it's not enough to consider only temperatures
when studying the effects of global warming. One must also take
into account the air conditioning effects of moisture, along with
another part of the picture -- warm regions are often separate from
Although some changes arising from global warming
are benign or even beneficial, weather extremes, such as floods,
can have significant economic impact.
The IPCC estimates that restoring vegetation to its
natural state would reduce CO2 by only 5-10 percent in
2100, so there is a strong case to be made for slowing the projected
rates of climate change from human influences.
Increased use of renewable resources -- such as solar
power -- and increased energy efficiency are seen as key steps to
aid in diminishing the rate of climate change Trenberth said --
and, subsequently, achieving a more sustainable world.