Notsofantastic
Actually it is quite simple to measure the geothermal gradient and energy balance. For example there have been numerous deep boreholes drilled into the Earth's crust, both in the oceans and onland, and measurement of the geothermal gradient occurs routinely.
In addition, there has been very extensive measurement of ocean temperature such that the global ocean heat flux is now well constrained.
Finally, deep earth geophysics tells us how much radioactive material there is down there in the core, so it is quite easy to calculate how much heat is being released.
There are various other ways too - trust me, it's covered (I can send you scientific articles to this end if you wish)
All of this suggests that the amount of energy being released is trivial compared with the solar flux. Of course it is much greater than that being released by humans - but it is not our release of heat that is the problem - it is the release of gases that then cause trapping of energy. An analogy would be old fashioned airliners with manual controls - when you move the joystick it is not the energy input that you put into the system that actually turns the aircraft, it is the effects of that input in terms of deflecting the ailerons that turns the aircraft. Same with global warming - it is not our heat output (which is trivial) but the by-products - gases - that are causing change.
Yes, we do face numerous extinction possibilities (not sure what you mean by Deccan traps though - the Deccan Traps are a volcanic area of India that erupted 60-65 million years ago, now essentially inactive), but all are very low probability. Global warming is on a different probability level, although to say that it is likely to cause human extinction is really scare-mongering.
I still think you are missing the point of the article (see my original posting). The article considered European airspace over a small area - i.e. lot's of short trips at relatively low altitude. It did not consider transatlantic service, which would yield very different results. Of course if you compare a single long haul trip (i.e. your trip today) at high altitude you will get very different results. I will be very interested to see how different though?
Finally, I should reiterate that this was a scientific paper exploring possible scenarios. The authors did not advocate that airspace changes like this should be undertaken, just opened up the debate about possible measures that could be employed. Science advances through hypothesis setting and validating / rejection. That is rather different from stating that this is the measure that should be employed. I agree though that the New Scientist interpretation was unhelpful.
Notsofantastic - if you would be interested in exploring whether we could put together a scientifically-valid argument, perhaps using the sort of data to which you allude, against the contents of the paper then please contact me directly. I would be very happy to help you do this (research is my expertise).
DrDave