This is a lengthy piece which requires some attention
and time. Since many will get lost reading it
I want to bring my conclusion to the fore.
My points are the following:
1) global warming is happening.
2) significant changes in the earth's average surface temperature have been
occurring for several million years and were obviously unrelated to human activity.
Ice ages and global warming are natural occurrences.
3) presently the polar ice caps on earth are melting but so is the southern
polar ice cap on Mars.
4) little of the greenhouse gas including carbon dioxide (which gets a lot of
attention as a cause of global warming) comes from human activity.
Is Global Warming Really Happening?
There is substantial melting of the polar ice caps so something is going on.
The second question is: what causes global warming or, more accurately, what
causes long-term (multi-decadenal) changes in temperature? The answer, unfortunately,
is quite complex.
Global Warming
This is a lengthy piece which requires some attention
and time. Since many will get lost reading it
I want to bring my conclusion to the fore.
My points are the following:
1) global warming is happening.
2) significant changes in the earth's average surface temperature have been
occurring for several million years and were obviously unrelated to human activity.
Ice ages and global warming are natural occurrences.
3) presently the polar ice caps on earth are melting but so is the southern
polar ice cap on Mars.
4) little of the greenhouse gas including carbon dioxide (which gets a lot of
attention as a cause of global warming) comes from human activity.
Is Global Warming Really Happening?
There is substantial melting of the polar ice caps so something is going on.
The second question is: what causes global warming or, more accurately, what
causes long-term (multi-decadenal) changes in temperature? The answer, unfortunately,
is quite complex.
The Sun as the Source of Energy
To make things simple the sun shines down on the earth and the earth reflects
back some of that energy and traps some of that energy. For the sake of simplicity
the primary thing which determines how much of the sun's energy gets trapped
in the atmosphere is what is called greenhouse gas. The expression "greenhouse
gas" is a reference to the fact that a greenhouse is designed to trap part
of the incident solar energy as a form of natural heating because plants like
a certain amount of heat.
Greenhouse Gas
So what controls temperature on the earth and consequently global warming? The
answer is - two things. The energy from the sun and the amount of greenhouse
gas in the atmosphere.
The largest percentage of the effect of greenhouse gas comes from water vapor
which is naturally occurring. Less than 20% of the greenhouse effect comes from
carbon dioxide.
There are only two things which can be responsible for global warming: the energy
incident on the earth from the sun is increasing and/or the amount of greenhouse
gases in the air is increasing.
Not Quite a Circle
First let's deal with the sun since that is apolitical. There are two things
which could make the incident energy from the sun change with time: one is the
sun outputting more or less energy and the other is a lot more subtle. Let's
take the subtle part first. Everyone knows that it is hotter during the day
that it is at night. The reason is obvious the earth rotates on its axis and
the sun rises and sets. It is warm in the day because of solar energy. It is
also warmer during the summer than during the winter. The reason is that the
earth is tilted on its axis (the line from the north pole to the south pole)
relative to its ecliptic (the orbital plane). You can observe this because the
sun is more directly overhead in the summer than it is in the winter.
There are two effects here:
1) the days are longer in the summer and
2) the sunlight has, on the average,to pass through less atmosphere (which
attenuates the effect) in the summer.
That got a little windy but the point is that everyone knows that summer and
winter happen even if they don't exactly understand why. Also, no one thinks
that global warming is indicated by the fact that it is hotter in the summer
and no one thinks that global warming is going away because fall is here and
winter is approaching. The longer-term effects we call
global warming/ice ages are, largely, more subtle versions of day/night and
summer/winter.
Sunspots?
Apart from day/night and summer/winter variations there are two factors which
affect the energy incident on the earth from the sun. The energy output of the
sun is not constant. Spacecraft observations show the Sun's output varied by
0.1%
during the past 11-year solar activity cycle. While sunspots have an 11 year
cycle the magnetic polarity of the sun inverts every cycle giving it a 22 year
"grand cycle." Sunspot activity has been increasing since 1700. See:
http://earthobservatory.nasa.gov/Library/SORCE/sorce_03.html
Sunspots indicate greater total energy being output by the sun and, consequently,
reaching earth.
A Guy with a Lot of Time on His Hands
So much for the obvious. There are three other factors which affect the energy
of the sun incident on the earth and this is where we need to credit a Serbian
mathematician named Milutin Milankovitch who in 1911 started working on a mathematical
model to explain the fact that the earth has had ice ages and successive periods
of global warming. He had 600,000 years of geological data to work with. What
is amazing is that this guy worked for 30 years without the aid of computers
and developed a near-complete model. His calculations were based on the fact
that there are 3 cycles in the relationship between the
sun and the earth:
1) the shape of the earths orbit around the sun changes with a periodicity
of 96,000 years.
2) The earth is tilted on its axis (currently 23.5 degrees) but that changes
from 21.5 to 24.5 degrees with a periodicity of 41,000 years and
3) the earth's axis of spin (the north pole is currently pointed at the north
star) wobbles with a period of 23,000
years.
When he published his work in 1941 there was some excitement but that was a
bad time for science because the world was preoccupied at the time. In the late
1960's geologists were able to study deep-sea sediment cores going back several
million years and the results validated Milankovitch's work. In fact these are
referred to as Milankovitch cycles. Milankovitch's
theory while not perfect (there are cycles predicted but not observed) is the
basis for long-term (tens of thousands of year) cycles of global warming and
ice/ages.
Latest News from Mars
The thesis that the global warming may have more to do with the sun than the
earth's atmosphere and human activity got a boost this week from the Mars Global
Surveyor Project which stated, "for three Mars summers in a row, deposits
of frozen carbon dioxide near Mars' south pole have shrunk from the previous
year's size, suggesting a climate change in progress."
The density of the Martian atmosphere is 1% that of the earth and is comprised
mostly (95%) of CO2. I would offer the strong
opinion that global warming on Mars is not caused by anything we are doing on
earth.
Global Warming Becomes Political
Despite the fact that we know that there are long-term periods of Ice Age/global
warming cycles we have at hand the socio-political interest in ecology and recognition
that people have an effect on the health of the planet.
Anthropogenic CO2
Any contemporary discussion about global warming deals almost exclusively with
anthropogenic (man made) CO2 and the thesis is that an abundance of anthropogenic
CO2 is responsible from global warming.
A Concrete Problem
There are 155 billion tons of CO2 pushed into the atmosphere each year. How
much of this is man-made? Come on... guess...
4%. 90 billion tons comes from the oceans (a gigantic sink/source of CO2). 60
billion tons come from plants. Less than 6 billion tons come from human activity.
There is one gigantic source of anthropogenic CO2 which is hardly ever discussed.
That is the manufacturing of cement. Cement manufacturing is responsible for
about 25% of all man-made CO2. In short, the percent of non-cement human generated
CO2 is about 2.5% of the annual amount of CO2 pushed into the atmosphere.
In addition CO2 is not the only greenhouse gas. Water vapor is also responsible
for heat trapping. Man-made CO2 is responsible for about 0.8% of the increase
in greenhouse gas.
Deforestation
There is another side and that is sequestration of CO2 by trees and other plants.
CO2 is reduced from the atmosphere by photosynthesis and it is also dissolved
into the oceans. Here the issue is that deforestation reduces the amount of
CO2 removed from the atmosphere by about 1%. Mankind thus affects the amount
of CO2 by 5%. 1.5% from cement, 1% from deforestation and the other 2.5% from
energy and transportation.
The questions then are 1) is the 0.8% (20% of the 4%) that we contribute "the
straw that broke the camel's back?" and 2) what can we do about it.
I believe that what has happened with global warming is an example of science
by consensus. It is fashionable to advocate global warming with the implication
that it is man-made and that we can make changes in our behavior which affect
it. The problem is that this conclusion is drawn without taking into account
the science involved.
Good Intentions Are not Good Science
This is a generation which looks at what is wrong with the planet and concludes
that we have screwed things up and we want to do things to correct that. This
is fine. It is an expression of good intentions. The air in L.A. is cleaner
than it was in the
'60's. Endangered species have protection. CFCs were recognized to lead to ozone
depletion and the "Montreal Protocol on Substances that Deplete the Ozone
Layer" was negotiated and signed by 24 countries in 1987. The ozone hole
over Antarctica is now shrinking. There is a big difference here - CFC's were
almost totally
man-made. CO2 is 4% man made and is only 20% of greenhouse gas.
Conclusions
Global cooling and warming have been happening for few million years. The root
causes have likely been the variation in
the energy output of the sun and the Milankovitch cycles. Absent a much better
understanding of the interactions among the atmosphere, the oceans, the clouds,
and plant and animal life we should recognize that our contribution to global
warming is minimal. 96% of the CO2 pushed into the atmosphere comes from flora
and the oceans. Has man's small increase
unbalanced a natural process or is the increase in non-anthropogenic CO2 the
result of higher temperatures generated by increased solar radiation associated
with increasing sunspot activity?
We should spend money on basic research with the purpose of better understanding
the interactions between the oceans and the atmosphere, plants (and animals)
and the atmosphere, cloud physics, a better Milankovitch model, and the effect
of
volcanoes before we spend any significant amount of money on the abatement of
anthropogenic CO2.
Political correctness must take a back seat to science. Science needs to explain
global warming and it needs to do so without predisposition as to the causes.
================================
Dick Lepre