* I just spent all day reading and hearing global-temperature experts, theories, observations and explanations. It appears that the temperature history is not explained simply by green-house gases, giving comfort to the climate deniers but not justifying dismissal as hoax.
* Sun variations cause significant temperature departures from green-house expectations, possibly starting a new cooling phase despite CO2 rise. We'll have to wait to see whether mountain snow caps return, glaciers stop receding, acrtic sea ice returns, coral reefs stop bleaching, permafrost stops collapsing and releasing methane, sea levels return.
* The deniers seem to misunderstand ocean acidification.
An example of numerous "hockey-stick temperature histories" can be seen at:
https://en.wikipedia.org/wiki/Hockey_stick_controversy
Useful explanations of global-warming dynamics are in the following 4 paragraphs from an article: What East Anglia's E-mails Really Tell Us About Climate Change, by Peter Kelemen, in Popular Mechancs, Dec 17, 2006. Found at: http://www.popularmechanics.com/science/environment/a5154/4338343/
* For these reasons, and based on carbon isotope data, it is all but certain that the present, unprecedented rise in CO2 is due mainly to human output. But one cannot rule out with complete certainty other factors, for example, global warming itself, that could also be significantly contributing to the atmospheric CO2 increase.
* CO2 (and methane) in the atmosphere are nearly transparent to UV and visible radiation, but absorb in the infrared, creating a "greenhouse." If it were not for this, the surface of the Earth would be much colder. This leads to the inference that increasing CO2 will lead to increasing warmth. Also, high CO2concentration in the air leads to ocean acidification, which is probably bad for coral and perhaps also for plankton that make their shells from calcium carbonate (soluble in acid) and form the base of the ocean food chain.
* A good-faith effort has been made to determine average global temperature using the instrumental record, with increasing accuracy and precision as the data become more comprehensive. For sure, the average temperature of the atmosphere has been rising for most of the last 50 years. This is consistent with the greenhouse theory, though one cannot rule out with complete certainty that other factors--variation due to sunspot activity, or the last gasp of a long warming trend caused by variation in the Earth's orbit--might also be contributing to temperature change.
* The Arctic ice cap is getting smaller, in apparent response to this global temperature increase. Sea level is rising, due to the thermal expansion of the oceans and, increasingly, to melting of the Greenland and/or Antarctic ice caps. It has been shown to most people's satisfaction that the Greenland ice cap is getting smaller.
