Good research. I had to do a bunch too to look at some of your points.
I am going to take a stab at it. Agreed that this is more or less a relative new field of research so that much more research and discovery will have to be done before anything conclusive is out.
I am going to go down the list you have made and offer counter points.
Maybe planetologist or astronomer could offer some points here, but I think comparing Earth's climate and CO2 concentrations to Mars isn't very conclusive. Much like I will point out later, and what you would called circumstantial evidence. Two planets that are completely different from the meteorology and developmental stand point. As you pointed out, Mars has 95% Carbon Dixiode and Earth only has 0.0383% (383ppmv), that single variable alone would make comparison point less. Also to note that Mars' orbit sits on a off set circle around the Sun, which makes its termperature variance greatly depending on which point in the year (orbit) it is. Mars' perihelic distance is 204 million kilometers and aphelic distance is 247 million kilometer. Unlike Earth that sits on a relatively consistent orbit about 150 million kilometer from the Sun. (Note, Mars is also like Earth where the planet is tilted at around 25 degrees, so Mars experience seasons as well.)
http://www.windows.ucar.edu/tour/lin...ars_orbit.html
http://cmex.ihmc.us/SiteCat/sitecat2/mars.htm
You are completely correct that the Sun has cycles of 11 years. Some scientist argue that it might be 22 year cycles. Again, since we have only recently begun monitoring the Sun with Satellites it is hard to have any conclusive evidence except that we know it is cyclical. So with only a few decades of data from Satellites we can not be sure what and how it attributes to Global Warming.
Although Stanford's researchers with National Oceanic and Atmospheric Administration agreed that even with the the account of the Sun Cycles, it still does not account for the average 0.6 C Degree raise in temperature in the past 100 years and 0.4 C in the past 25 years.
http://solar-center.stanford.edu/sun...glob-warm.html
http://lwf.ncdc.noaa.gov/oa/climate/globalwarming.html
NASA Goddard Institute for Space Studies even went as far as saying that Sun cycles can not be responsible and these increases in temperature must be attributed to greenhouse gases.
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Originally Posted by NASA
Many scientists have argued that the radiation change in a solar cycle — an increase of two to three tenths of a percent over the 20th century — are not strong enough to account for the observed surface temperature increases. The GISS model agrees that the solar increases do not have the ability to cause large global temperature increases, leading Shindell to conclude that greenhouse gasses are indeed playing the dominant role.
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http://www.giss.nasa.gov/research/news/19990408/
And in regards to the Sea levels, the article you quoted states that Sea Levels Arctic Sea levels dropped by 2mms but Globally they have risen.
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Originally Posted by BBC
. . .ocean waters are shown to have gone up across the planet by 3.2mm per year for the period 1992 to the present.
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http://news.bbc.co.uk/2/hi/science/nature/5076322.stm
And . . .
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Originally Posted by NOAA
Global mean sea level has been rising at an average rate of 1 to 2 mm/year over the past 100 years, which is significantly larger than the rate averaged over the last several thousand years.
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http://lwf.ncdc.noaa.gov/oa/climate/...arming.html#Q9
These figures are clear, there is no ambiguity about that:
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Originally Posted by C&EN
Analyses of trapped air show current CO2 at highest level in 650,000 years . . . The data indicate that the current concentration of CO2, at 380 ppm, is 27% higher than the preindustrial level and higher than any level attained during the past 650,000 years.
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http://pubs.acs.org/cen/news/83/i48/8348notw1.html
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Originally Posted by BBC
BBC News has learned the latest data shows CO2 levels now stand at 381 parts per million (ppm) - 100ppm above the pre-industrial average.
The research indicates that 2005 saw one of the largest increases on record - a rise of 2.6ppm.
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http://news.bbc.co.uk/1/hi/sci/tech/4803460.stm
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Originally Posted by NOAA
Pre-industrial levels of carbon dioxide (prior to the start of the Industrial Revolution) were about 280 parts per million by volume (ppmv), and current levels are about 370 ppmv. The concentration of CO2 in our atmosphere today, has not been exceeded in the last 420,000 years, and likely not in the last 20 million years.
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Now, I agree with you that the data definitely shows that Earth's eco-system is very dynamic. We definitely do not know what all this data sums up too.
As with most of these articles indicted from "experts" and scientist, all are in agreement that more research is necessary.
Maybe Earth's ecosystem could handle up to 1 Trillion tons of CO2 and other gases before it become irreversible. Maybe it could only handle 500 million tons. I don't know, we don't know.
But I believe that the jury is still out, are we "in fact quite insignificant"? As you asked? I believe in that this isn't a free ticket ride. Better to be guarded than "1 buck short and 2 days late".
Thus in this case, personally I choose to follow the
Precautionary principle.