First of all, congratulations on your well written post. I have a few remarks though.
You mention 2016 was the warmest year recorded in history. This means so much as that it was the warmest year since man started recording actual temperature (directly, with thermometers), which was only since 1850. 
As shown in the above image, Earth has experienced much warmer periods than the last few hundreds of years. I am not trying to debunk the idea of climate change. On the contrary, I am trying to show that climate change has been going on long before our species wandered this world. However, what we are doing is disturbing natural processes by emitting huge amounts of green house gases, cutting rainforests (and therefore increasing erosion and causing soils to become infertile, reducing many species' habitat causing them to become extinct), overfishing etc. and that all in a very short period on a geological time-scale.
You mention that Earth's only energy source is the sun. What about heat generated from radioactive decay by unstable isotopes in the Earth's crust, mantle and core?
You mention only a small percentage of heat energy from the sun gets to the Earth, though the figure you added shows 51% is absorbed by the Earth. It's debatable whether you would find this a small percentage or not ;)
I am looking forward to your reply and the second part of this series.
I am quite impressed that you read my post with utmost attention as to bring out these gray areas. Thanks a lot. Now let me address the issues raised one after the other:
About the earth experiencing warmer periods before now, you are quite right. Perhaps I should have said in the last few hundred years.
About heat generated from radioactive decay in the earth's crust, I do not know how much of heat generated becomes useful to the atmosphere really, you might want to enlighten me in that aspect
I mentioned that only small percentage of heat from the sun gets to the earth, yes. the 51% you are looking at is just a part of the small percentage that got to the earth. The 100% incoming solar radiation is actually a small percentage of original radiation from the sun. A large part has been absorbed or reflected back into space by the cloud and ozone layer.
I will like to hear further from you.
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https://www.skepticalscience.com/heatflow.html
This link contains info about the different heatfluxes to the Earth's surface. Particularly figure 4. and comment 31. by Tom Curtis are quite useful. Turns out less than a per cent of the surface heat flow is coming from the Earth's interior (nowadays). My main point was to simply indicate there are more sources of heat than just the sun :)
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I agree, this post is very nice!
I was about to shoot a comment along the same lines of yours, concerning the dates. But you were first. ^^ The actual problem consists of the changes induced by humans, as you said, which thus focus on a smaller time scale. :)
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I agree there are nature's automated changes to climate since the inception of the earth, the focus here is the human-induced changes that serve to disrupt the automation. The consequences might be more disastrous in the long run.
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