Climate Any discussion
of climate must necessarily begin with an understanding of the
term:
climate: the
prevailing or average weather conditions of a place, as
determined by the temperature and meteorological changes
over a period of years.[1]
Key to climate, then, are "conditions
of a place," and, "changes over a period of years." When speaking
of climate on a global scale (e.g., "global warming" or "global
cooling"), the term necessarily becomes quite generalized due
to the wide fluctuation in climate from place to place. Thus
we see more of averages when looking at climate globally. If
the issue is one of "global warming" (or "global cooling"),
then it is safe to say that we have reduced the scope of climate
to the key element "changes over a period of years." Commencing
with the earliest known existence of a variety of complex life
forms (about 600 million years ago), scientists divide earth's
history into eras. These time segments are known as the
Paleozoic, Mesozoic, and Cenozoic eras.
Geologists further subdivide eras into periods (e.g.,
Jurassic the period in which dinosaurs first occurred
during the Mesozoic Era). The present falls within the
Quaternary Period (which began 1.8 million years ago)
of the Cenozoic Era (which began 65 million years ago).[2]Ice Eras, Ice Epochs,
Ice Ages Similarly, climatologists divide earth's climate
according to sustained periods of global warmth or global cooling.
The earth's "temperature is always changing ... so it only has
two choices -- going up or going down."[3]
From the Time-Life Books Planet Earth series "Ice Ages"[4]
(my emphasis added):
"Human beings
have never experienced the earth's normal climate. For most
of its 4.6-billion-year existence, the planet has been inhospitably
hot or dry and utterly devoid of glacial ice. Only seven
times have major ice eras, averaging roughly 50 million
years in length, introduced relatively cooler temperatures;
humankind arose during the most recent of those periods.
... Each ice
era encompassed several ice epochs -- periods
of still lower average temperatures. During the 65 million
years of the current ice era ... six ice epochs
have occurred.
Earth, then, is in an ice
era whose onset 65 million years ago marked the end of the
Mesozoic era and the beginning of the Cenozoic Ear.
The current ice epoch (which began 2.4 million years
ago) is known as the Pleistocene ice epoch and is the
seventh of this ice era. Earth's
Typical Climate & Global Warming/Global Cooling It is
worth noting that the climate typical of earth during most of
its 4.6 billion years (about 92% of earth's climate history)
is marked by much warmer and more humid conditions where no
surface ice exists, even at the poles. Dinosaurs evolved
and thrived during earth's typical climate. It is only during
ice eras, including the much cooler climate of today,
that such extensive surface ice can exist. The onset of the
Pleistocene ice epoch was accompanied by one of the coldest
periods of global cooling on earth. Such exceptionally cold
periods characterized by large glacial advances are known as
ice ages. Again, from the Planet Earth series,
"Ice Ages"[5]:
"The most recent
ice age ... preceded and followed by warmer times -- interglacials
-- began about 120,000 years ago. It reached a bitter extreme
some 50,000 years later, slowly moderated, then brought severe
cold again about 18,000 years ago. In the last 10,000 years
-- the Holocene interglacial -- three sustained cold
spells ... sent temperatures below the current global average
of 59°F. One of them, a time of crop failure and famine
called the Little Ice Age, ran from the 15th to
the 19th Century. ... The 100-year warming trend
that ended the Little Ice Age extended through the early 1960s
but ... it was followed by yet another drop in average temperature,
which ... lasted up to the [early 1980s]."
The Holocene interglacial
(which marks our current climate) experienced a number of marked
warming trends -- periods of global warming:
"Temperatures
peaked around 4000 B.C. and remained stable for about 2,000
years. During this period ... many regions were about 5°F
warmer on the average than they are today ..."[6]
The Medieval Warm Period,
which occurred between 800 and 1200 A.D., was marked by a sustained
period of "global warming" that saw the Northern Hemisphere
heat up to the extent that Vikings cultivated Greenland, Iceland,
and Newfoundland.[7]
Recent
Trends The chart[8]
(left) plots mean global temperature change from 1860 through
1985. Whenever the
trend of global temperature change over a period of years
is downward, global cooling is occurring; whenever the trend
is upward, global warming results. This chart shows a net
increase in global temperature from 1860 to 1985 of about
0.5° C (0.9° F). However, notable during this period
are two cooling trends (1867-1910 & 1943-1974) and two
warming trends (1910-1943 & 1974-1985).
One interesting observation from
this data is that, if the "calamitologists" are correct in their
assertion that man's burning of fossil fuels during the industrial
age (since 1860) is a dominating factor responsible for global
warming, then one would expect the trend of global temperature
change to have been increasing consistently with the increase
in fossil fuel burning. This has not been the case, suggesting
that the warming trends that have occurred since 1860 are most
likely dominated by other factors.
Causes of Natural Climate
Change Long before the advent of the Industrial Age and
burning of fossil fuels, global climate underwent changes that
produced both warmer and cooler periods. Indeed, mankind's entire
existence has been within an ice epoch of an ice era
-- modern man lives in an interglacial period of an ice
age. What then, causes climate to change? Scientists have
been wrestling with that question for many years and new theories
and understanding continue to emerge from the scientific community.
Some of the known influences on climate are:
The Atmosphere & Greenhouse
Effect - Clouds and water vapor are responsible for
"over 98% of the current greenhouse effect."[9]
Clouds and water vapor are also significant for their reflectivity,
i.e., they reflect a portion of sunlight that effectively
lowers potential heat absorption by the earth. Other greenhouse
gases (e.g., carbon dioxide, methane) are minor contributors
to the greenhouse effect.
The Lithosphere -
The earth's land mass constantly absorbs and radiates sunlight.
Long-term climate changes are significantly influenced by
continental drift that alters the position of landmasses
on the planet. Not only is continental position altered,
but also mountain building, ocean shrinkage and expansion,
and the distribution of landmass with respect to the tropics
and poles are all influential factors on climate and climate
change. Lithospheric reflectivity and absorption of sunlight
is highly dependent on surface conditions (e.g., the presence
of snow or rain, desert, plains, forest or cities), latitude,
and season.
The Hydrosphere, Ocean
Surface Temperature - The oceans account for 97% of
the hydrosphere and cover 71% of the planet. Except where
frozen into ice, ocean reflectivity and absorption only
changes with latitude and season. Despite el niño
and la niña currents which dramatically alter
warm and cold pools of Pacific Ocean surface temperature,
evidence suggests average equatorial sea surface temperature
has been relatively constant for billions of years, varying
only within +/-1°C.[10]
Astronomical - Planetary
Dynamics - There are three primary contributors to climate
change resulting from planetary dynamics. In Ice Ages[11]
these are described as:
The
100,000-Year Stretch - The orbit of the earth gradually
stretches from nearly circular to an elliptical shape
and back again in a cycle of approximately 100,000 years.
During the cycle, the distance between earth and sun
varies by as much as 11.35 million miles
[currently about 93 million miles].
The
41,000-Year Tilt - The earth's axis is never perpendicular
to the plane of its orbit; over the course of about
41,000 years the angle varies between 21.5 and 24.5
degrees. Because of the tilt, the solar radiation striking
any point on earth fluctuates during the yearly orbit,
producing seasons. When the tilt is greatest, summers
are hottest, winters are coldest.
The
23,000-Year Wobble - Even while the shape of its
orbit and the tilt of its axis are changing, the earth
wobbles slowly in space, its axis describing a circle
once every 23,000 years ... Because of this movement,
known as axial precession, the distance between the
earth and the sun in a given season slowly changes.
Today, for instance, the shape of the orbit places the
planet closest to the sun in the Northern Hemisphere's
winter and farthest away in summer. The combination
... tends to make winters mild and summers cool -- and
favors ice-sheet growth. However, 11,000 years ago,
the arrangement was just the opposite ... setting the
stage for the Northern Hemisphere ice sheets to decay."
Astronomical - Impacts
from Space - It is widely agreed in the scientific community
that an impact on the northern rim of Mexico's Yucatan peninsula
65 million years ago was instrumental in the demise of the
dinosaurs and was the single event that precipitated the
onset of the current ice era:
"Since 1980,
when Luis Alvarez, Walter Alvarez, Frank Asaro, and Helen
V. Michel proposed that a giant meteorite impact had caused
the extinction of the dinosaurs 65 million years ago,
such impacts have become fodder for movies, TV shows,
plays, and talk shows. The subject's popularity was enhanced
when Comet Shoemaker-Levy 9 smashed into Jupiter in July
1994, producing easily visible impact sites surrounded
by rings of clouds expanding at supersonic speeds.
"The destructive
force of an asteroid is daunting. A single bolide six
miles across (about the size of the asteroid that killed
the dinosaurs 65 million years ago) would hit Earth with
the force of about 100 million megatons of TNT, about
10,000 times greater than the world's entire arsenal of
nuclear weapons. If an object hit an ocean it would produce
tsunamis hundreds of feet high. The debris from such an
impact would carpet hundreds of miles of surrounding terrain
with house-sized boulders, while saturating the atmosphere
with dust for years."[12]
The resultant blanket of
dust and smoke from a giant impact would block solar radiation
for years, making daytime as dark as night. Photosynthesis
would cease and the foundation for maintaining life would
be severely eroded with mass extinctions ensuing. This is
precisely the scenario that accompanied the onset of the
current ice era 65 million years ago.
Volcanic - It has
long been noted that volcanic activity is sufficient to
alter short-term climate. As far back as 1784 Benjamin Franklin
suggested a connection between Iceland's cataclysmic eruption
the previous summer and atmospheric haze and an unusually
cold winter. Individual volcanic eruptions are insufficient
to effect long-term climate change, however, "some experts
believe that hundreds of eruptions over many centuries could
trigger another relentless advance of the world's ice sheets."[13]
Solar - Recent data
confirm that our sun is not constant in its energy output.
Much like a light dimmer can raise and lower the light (and
heat) given off by an ordinary light bulb, our sun has a
history of variability that is sufficient to create periods
of warmth and cold whose effects can be felt over decades
or centuries. Advocates of catastrophic global warming from
human activity have routinely dismissed solar influence
of this type as "minimal" or "inconsequential." Yet, the
solar variability influence is perhaps the leading candidate
to explain global climate changes in the recent past known
as the "Medieval Warm Period" and "Little Ice Age."
Solar variability will be
discussed in greater detail in Part
4: Warming - Greenhouse Effect & Nature.
Climate change is not a simple
process. There are many different factors that contribute to
the state of climate at any given time. No computer model exists
that begins to account for all the variables that produce our
climate; indeed, we simply haven't the knowledge to build such
a model. Clearly, then, the contribution of anthropogenic CO2
as a greenhouse gas is but a tiny fraction of a single ingredient
to but one of the many complex factors that cause climate to
change. Finally, given that:
The earth's typical climate
is much warmer than today's (at least 92% of climate history
is marked by much warmer climate), and,
Humanity's entire existence
has been within the Pleistocene ice epoch of an ice era
that began 65 million years ago, and,
Earth has experienced only
seven ice eras averaging 50 million years in length,
then, aren't we overdue
for this ice era to end as natural forces revert
earth's climate back to a typically much warmer and more
humid climate? It certainly would be worth examining this
possibility.
Unfortunately, science knows
little about what caused each of the previous six ice eras to
end. Consequently, we don't even know what to look for as evidence
of natural climate warming. We do know that warmer
eras in earth's history naturally produced CO2 levels
as high as 800 - 2400 ppm, three to nine times the pre-industrial
levels of CO2.[14]
Shouldn't we have some clue about what caused such natural elevations
of atmospheric CO2 before we simply assume
post-industrial CO2 elevations are solely due to
human activity (burning fossil fuels)?
Footnotes:
Webster's
New World Dictionary of the American Language, 2nd College
Edition, p 266.
Lambert,
David, Dinosaurs, pp 14-15.
Lindzen,
Dr. Richard S. (Alfred P. Sloan Professor of Meteorology,
Massachuesetts Institute of Technology) in an interview with
James K. Glassman (Kyoto
"Absurd" Says MIT Scientist) of Tech
Central Station, March 5, 2001.
Ice
Ages from the Time-Life Books series Planet Earth,
pp 20-21.
