SNIP>
>>>BTW the amount of heat being released from the Earth's Nuclear Core and combined with the radiant energy received from the Sun, makes man's output fade into insignificance.
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>>The issue is not about heat produced by man - which is indeed insignificant - but about gases, especially CO2, which are said to "trap" the heat from the sun.

I think you are mis-attributing the issue. It is not the "heat" generated by man, as far as I understand it, but rather the diminishment of the earth's capability to eliminate heat in general. I believe the increasing levels of CO2 are causing this.

I was a doubter of "global warming" for a long time, arguing (mainly) that the earth has had periods even hotter than now and there was not a single human being in sight!

But this time is different, primarily in that spikes observed in the past were annual or 2 year spikes, while we now have an ever-increasing warming exceeding a decade.

Just look at today...
- At least 5,000,000 cars in motion at any one time.
- At least 50,000 flights in motion on any given day.
- At least 5,000 coal-fired power plants running every day.
- At least 50,000 factories running every day.
- At least 5,000 oil wells now active.
- A tripling (more) of the population of the world in the last 150 years, many needing to heat their homes seasonally and needing to cook food daily.

All of the above were 0 (or much smaller for the last) 150 years ago and the eternity before that. To argue that these factors are insignificant is to truly have one's head buried in the sand.

Maybe the earth does flip on its axis (some believe it did at least once already) and we are all doomed anyways.
Maybe it's natural to have ice ages followed by warmth. Maybe the ocean currents shift from time to time making hot places colder and cold places hotter.
But, no matter how you slice it, "man" has to be having an impact on the planet's general operation. And it makes good sense that man would be doing himself a service by reducing that impact.

Our activities are in no way "natural" any more. Canada and the U.S. in particular saw the harmful effects that man's activities (we both no doubt took liberties that European/Asian countries knew better of) in pollution of the Great Lakes and deaths of smaller lakes because of acid rain. These have largely been addressed such that the Great Lakes are now looking good again and lakes have started to rejuvenate. And my point is that if the relatively small population/activity near the Great Lakes can cause such impacts, why would anyone doubt the deterioration of the planet's natural systems?
These effects were directly observable/measureable, so there was little argument and lots of willingness to correct the situation.

Scientists have the benefit of satellite measurements and complex computer modelling and widespread field measurements now in place. Scientists now have capabilites to analyze ice cores and soil/rock cores to make detailed determinations about the past operation of the planet. Scientists can now communicate very efficiently and across the entire planet. There are nmore scientist alive today than the sum of all the scientists that lived in the past.
Scientists have always disagreed, and it has happened that scientists ostracized by the community because of a theory have ultimately been proven right and the colleagues wrong.
"Global warming" was close to such a theory. The early promoters were soundly criticized almost universally, but as evidence mounted support grew. Today it is the vast majority of scientists who acknowledge the existence of the problem and most fear that time is short to formidably address the problem before the process becomes irreversible.

Until the present time it was rare that government or business interfered with the findings of the scientific community. But that has changed radically over the last 15 years or so. And do remember that virtually all communications are controlled by either business (the vast majority) or government, and business has shown itself and government that 'the message' will become "fact" if spread frequently enough and widely enough.

There will always be dissenters, and it is an attractive proposition to many to be such today given that they will be called upon to air their views in the media and attend conferences all over the world and make nice money from book sales, etc. It's gotta be a real nice way to make a living.

But, in the end, it all comes down to, for me, how I feel about what I'm leaving behind for my grandchildren and their children. While the poor state of society is a bad enough legacy, the thought of leaving them a dying planet is just too much.

Jim