[cogitator]

First, the major premise contains an unproven assumption that the current postulated warming is not part of a natural statistical variation.

There are many indications that the current warming trend is not due to natural variation (primarily).

Conclusion: Changing human activity will stop global warming.

Hansen is actually a believer in alternate energy and new technology as the best way to address the situation.

Conclusion: Prudence demands implementing this change immediately.

Hansen has expressed the viewpoint that humanity, collectively, has a decade or so to start doing something substantial about global warming or irreversible changes with the potential to induce significant-to-severe climate alteration in the future will become much more probable.

In fact, ice core drillings have indicated that the earth has been warmer as well as cooler than it is now a number of times in the past without catastrophe.

Define "catastrophe" in this context. For the glacial-interglacial era, there have only been a few short periods during prior interglacials that were slightly warmer than now -- without the higher CO2 concentrations in the atmosphere that will contribute to even higher temperatures. So the Earth may be on the verge of entering an unprecedented climate state.

[Lucky Dog]

Hansen is actually a believer in alternate energy and new technology as the best way to address the situation.

One believes in a theological proposition. Scientific judgments are properly based upon facts and logic not belief.

My point is, very simply, that there is insufficient evidence that so-called, global warming is anything other than a naturally occurring phenomenon. Consequently, it is both premature and unfounded to assume that humankind can do much, if anything, to either mitigate, or exacerbate it.

Hansen has expressed the viewpoint…

As it is based upon unproven supposition as to the causes of so-called global warming (if such even exists), Hansen’s viewpoint is scientifically extraneous and irrelevant.

For the glacial-interglacial era, there have only been a few short periods during prior interglacials that were slightly warmer than now --

This statement, alone, logically destroys the argument that so-called global warming is, conclusively and exclusively, the result of human activity. If the global temperatures at any time prior to the industrial revolution were ever equal to, or warmer than the present, then there are obviously natural mechanisms which were responsible for that increase and could be so, again, in the present.

So the Earth may be on the verge of entering an unprecedented climate state.

Then, again, it may not…