"A faith that can not survive collision with the truth is not worth many regrets" - Arthur C. Clarke
In light of Dr. Scotese's chart, we can make the following observations:
1. Ever since the Pre-Cambrian period --some 650 million years ago-- there appears to be an average global temperature maximum of 22 degrees C (or 72 degrees F), and an average global temperature minimum of 12 degrees C (or 54 degrees F) ...except for a "blip" at the end of the Permian period. --The earth may have some capacity of "buffering" temperature swings wider than these maximums and minimums.
2. Considering the total time that all the major phyla of complex multicellular life have been on earth (starting with the "Cambrian Explosion," 550 million years ago), the average historical global temperature has been about 18 degrees C (or 66 degrees F). -- This means that today's average global temperature is near to its lowest historical average ever since complex life has been on earth, which is about 6 degrees C (10 degrees F) lower than the historical average.
3. Comparing the combined times of having relatively warm versus cool temperatures during the past 550 million years --starting with the Cambrian-- about 20% of that time has been cooler on average, while 80% of that time has been warmer on average. --Ever since complex life has been on Earth, the average global temperature has been at its warmest four times more than at its coolest.
4. Over the past 550 million years, if we combine the periods with coldest average temperatures (where the graph holds at 12 degrees C, or 54 degrees F), this adds up to about 10% of the time. --- But if we combine the periods with the hottest temperatures (holding at 22 degrees C, or 72 degrees F), the global temperature has held steady at its hottest about 50% of the time.
-- So, during most of the time that complex life has been on earth, world temperature has remained steady at its hottest five times more than at its coldest. And when the earth's temperatures remain at the coldest, it is for a relatively short duration.
5. It is evidently true that the average temperature today is rising, however, the world has relatively recently come out of a couple of "Ice Ages" (avg. temp. of 12 degrees C, or 54 degrees F), and the average world temperature historically had only "one way to go" after the Ice Ages --upwards-- in which the current "upswing" is only about 1 degree C higher than average Ice Age temperatures.
6.Though the earth's average temperature seems to be edging upwards, it must still increase by an additional 6 degrees C (10 degrees F) to reach the even the historical average for the past 600 million years.
7.Mammals have been on earth for about 200 million years, with average global temperatures being in the cooler part of the scale only 15% of that time --however, 85% of the time it has been in the warmer part --and in fact, 45% of the time (90 million years) mammals have been on earth while the global temperature held at its maximum average. -- As mammals, we humans being alarmed by the current rise in global temperature averages may be an unnecessarily fearful over-reaction.
8. The earth's average global temperature has currently held near the minimum temperature for about 5 million years --and ever since the start of the Cambrian (550 million years ago) it has not stayed at that minimum for a longer time than that. --So: According to historical patterns for the past 650 million years, the average temperature is now due to go upwards... and this historical pattern reaches very far back before the presence of mankind.
Carbon Dioxide In the Atmosphere
A major concern for many people is the amount of carbon dioxide (CO2) which is ending up in the atmosphere from various sources including the combustion of fossil fuels by humans, and whether this has a dangerous affect on global temperature. The data represented by the following chart shows the amount of atmospheric CO2 along with the average global temperatures (also from C. R. Scotese, as above), such that the following observations seem appropriate:
1. During the Cambrian Period, global atmospheric CO2 levels varied between 16 to 25 times higher than they are today, yet average global temperatures held at the highest levels for millions of years; they did not follow the CO2 variation.
2. During the last half of the Ordovician Period (for about 25 million years), global CO2 levels steadily increased from 13 to about 15 times higher than they are today, and yet global temperatures dropped down to the coldest average they have ever reached since higher life has been on earth.
3. During the Silurian period, atmospheric CO2 levels dropped from 15 down to 10 times today's levels, and yet global average temperatures started at the coldest and rose to the global maximum during that period.
4. During the first half of the Carboniferous Period (appr. 35 million years), global atmospheric CO2 levels dropped to being almost equal to CO2 levels of today, and yet average global temperatures still held at about 2 degrees (C) shy of the global maximum.
5. The Permian, Triassic Periods may seem to reflect a loose sort of parallel "cause-and-effect" relationship between global atmospheric CO2 levels and average global temperatures --while the Jurassic does not seem to demonstrate such a relationship....
6. ... however, through the Cretaceous period, while global CO2 levels fairly steadily dropped for about 80 million years (ending at almost as low of levels as we have today), the average global temperatures climbed back up to the highest average temperatures ever seen since higher life has been on earth, and stayed there for 70 million years. --This may be seen as an example of an inverse relationship (or somewhat of a non-relationship) between CO2 levels and global temperatures.
1. During the Cambrian period there was a "sudden" appearance of almost all the major classifications (phyla) of life (including all the body-plans of life) which have ever existed on earth --and this occurred with CO2 levels which were 16 to 25 times higher than today's levels, as well as the average global temperatures staying at the highest average levels that higher life has ever seen. Therefore, evidence would seem to indicate that such atmospheric conditions and temperatures do not appear to not be a negative --but may be a positive-- for higher life on earth.
2. In light of especially the Ordovician temperature-drop (while CO2 levels remained quite high), and the Cretaceous temperature-rise which then remained at the maximum for about 70 million years (while CO2 levels steadily dropped), --along with other discontinuities (like the first half of the Carboniferous) mentioned above-- there often appears to be little relationship in which global temperatures follow changes in atmospheric CO2 levels in a cause-and-effect direction ...sometimes even appearing to be an inverse relationship (or a non-relationship).
3. Despite relatively high or relatively low CO2 levels in the atmosphere, the earth seems able to maintain a maximum average temperature, above which the high CO2 levels do not make temperatures rise. --The earth may have some temperature buffering/regulating capacity ...which may be basically unrelated to the CO2 content in the atmosphere.
4. Despite relatively high CO2 levels in the atmosphere (during some periods), something seems able to cause the earth's average temperature to fall to its lowest relative temperatures regardless of high (or low) CO2 (see the second half of the Ordovician period for this).
5. With the above data considered, there often does not seem to be a strong and direct cause-and-effect relationship between CO2 levels in earth's atmosphere and the average temperatures of earth's atmosphere.
Sun Activity and Global Temperatures
Another factor which should come under very serious consideration is the power of the sun's radiation to directly affect average global temperatures.
The well-known rapid and sizeable rise and fall of atmospheric (and climatological) temperatures on a daily (and seasonal) basis --as demonstrably caused by solar radiation-- should make this solar radiation factor a very obvious front-runner in the issue of such temperatures.
Consider this graphic table (to the right), which was put together by Nigel Calder and published in 1998 in "The Carbon Dioxide Thermometer and the Cause of Global Warming."
Calder presented this analysis at a SPRU (Science and Technology Policy Research) seminar at University of Sussex, Brighton, England on October 6, 1998. The strength of solar wind was used as a measure of sun intensity.
The following observations seem to follow:
1. This data covers a period of about 125 years (from 1865 to 1990), which some might consider to be of somewhat limited usefulness in being able to draw conclusions --especially compared to the longer-term data given in the two tables above-- but neither is it insignificant when one considers the sheer power of solar radiation.
2. Still, over the 125-year period, there is a fairly obvious concurrence of average global temperatures along with the varying strength of the sun's activity and radiation ---when the high and low spikes of global temperatures are averaged out.
3. This fairly close concurrence of solar energy strength along with average global temperatures seems to be a good cause-and-effect relationship which is fairly well demonstrated in this table.
Admittedly, the evidence seems to indicate that some global warming has been occurring over the past century or so, however, it seems much more advisable to connect that rise in the average global temperature to the activity of the sun (for example, look up "solar cycles" and "solar maximum"), rather than primarily attributed to the levels of CO2 in the atmosphere. This appears to be true in light of the above data collected by Calder, as well as significant "disconnects" in the relationship of global CO2 in relation to global temperatures, as demonstrated by the data above from Scotese. --At any rate, the rise in temperature may not be largely due to human activity.
In view of this, it seems wiser to possibly attempt to do something reversible about repelling/deflecting or reducing the absorption of sun radiation by the earth's surface (such as white rooftops and roadways) --rather than doing damage to whole economies in efforts to force a reduction in man-made CO2 levels.
... However, --that said-- it would probably be especially foolish to do something like dispersing massive and extensive clouds of reflectors/particulates in high orbit around the earth to reflect solar radiation because it would be very difficult to undo such a situation, and it might do long-term damage to the environment/climate.
Such information may be helpful in giving direction to discussions on "climate change."
In a January 2012 letter in the Knoxville News Sentinel, entitled "Global Warming Proven to be Myth," Dr. Arvid E. Pasto (with Oak Ridge National Laboratory), says that human-caused global warming is not substantiated, and carbon dioxide by itself is not a very important greenhouse gas anyway, but water vapor is actually much more significant to the earth's temperature.
-- In view of this evidence, it may be more important that mankind properly manage its forests and plantlife (eg, deforestation) --and vigorously combat environmental pollution, poisoning, exploitation and destruction, rather than be overly concerned about CO2 levels in the atmosphere.
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