The burden of proof for Anthropogenic Climate Change falls on alarmists. Climate Change (CC) has been ongoing for millions of yearslong before humans existed on this planet.
Obviously, the causes were all of natural origin, and not anthropogenic.
There is no reason to believe that these natural causes have suddenly stopped; for example, volcanic eruptions, various types of solar influences, and (internal) atmosphere-ocean oscillations all continue today. (Note that these natural factors cannot be modeled precisely.)
Lets call this the Null Hypothesis. Logically therefore, the burden of proof is on alarmists to demonstrate that the Null Hypothesis is not adequate to account for empirical climate data; alarmists must provide convincing observational evidence for Anthropogenic CC (ACC)by detailed comparison of empirical data with GH models.
I am not aware of such proofs, only of anecdotal infoalthough I admit that ACC is plausible; after all, CO2 is a GH gas, and its level has been rising, mainly because of burning of fossil fuels.
However, ACC appears to be much smaller than predicted by GH models; there is even believed to be a period of no warming [hiatus] during the past 19 yearsin spite of rapidly rising atmospheric CO2 levels .
There seems to be no generally accepted explanation for this discrepancy. Yet as the gap grows, the five IPCC reports insist there is no gapwith ever greater claimed certainty; rising from 50% to 99%.
Even necessary conditions for empirical data (like temperature rise vs altitude and latitude; cloud cover; precipitation) are difficult to establish; any major disagreement with models disproves ACC.
IPCCs GH models are not validatedand not policy-relevant
In other words, GH models have not been, and may never be validated; hence are not policy-relevant. They are scenario-generation machines that rest on assumptions and incomplete sciencenot on actual observations .
Anyway, warming appears to be trivially small, and most likely economically beneficial overallas established through careful studies by leading economists.
I therefore regard the absence of any significant GH warming as settled, and policies to limit CO2 emissions as wasting resources needed for genuine societal problemsand even as counter-productive, since CO2 promotes plant growth and raises crop yields 
Surviving a coming climate cooling
I am much more concerned about a cooling climate, as predicted by many solar scientists , with its adverse ecological effects and severe economic consequences for humanity.
Singer and Avery  have described the cyclical CC, seen during the past major glaciation; Loehle and Singer  see evidence for extension of the cycles into the current Holocene.
In particular, historical records  identify the recent cycle of a (beneficial) Medieval Warm Period and the (destructive) Little Ice Age (LIA) with its failed harvests, starvation, disease, and mass deaths.
I have therefore explored ways  to counter the (imminently expected) next cooling phase through low-cost and low-ecological-risk methods of a specific GH effectnot based on CO2.
At the same time, assuming that our scheme does not work, we need to prepare for adaptation  to a colder climatewith special attention to supply of food, and of sustainable water and energy.
The outlook appears promisingprovided there is adequate preparation. However, the coming cold period will test the survivability of our technological civilization.
As surmised earlier , COP21 will likely turn out to be a big nothing-burger, but media will spin it as great Obama victory. US consumers will pay the bill and suffer higher energy prices and increasing poverty.
1. Singer, S. Fred. "The Climate Warming Pause Goes AWOL (Or Not)". American Thinker, June 4, 2015.
2. Bast, Joseph L. Private communication, November, 2015.
3. CCR-IIb, Why Scientists Disagree about Global Warming: The NIPCC Report on Scientific Consensus, November 30, 2015.
4. Soon, Willie, Cornelis de Jager, Valentina Zharkova, et al.
5. Singer, S. Fred and Dennis Avery. Unstoppable Global Warming: Every 1500 years. Lanham, MD: Rowman & Littlefield, 2007.
6. Loehle, Craig and S. Fred Singer. "Holocene temperature records show millennial-scale periodicity". Canadian Journal of Earth Sciences, 47:13271336, 2010.
7. Lamb, Hubert H. Climate, History and the Modern World. New York: Routledge, 1995.
8. Singer, S. Fred. ""Saving Humanity from Catastrophic Global Cooling: A Task for Geo-Engineering". American Thinker, May 14, 2015.
9. Singer, S. Fred. ""Surviving an imminent ice age". American Thinker, November 29, 2015.
10. Singer, S. Fred. ""Obama Expected to Bind U.S. to CO2 Reduction at Paris Climate Meeting This Year". American Thinker, April 16, 2015.
[This paper was presented on the Heartland Institute panel, Hotel California, Paris, France. December 7, 2015]