Total extinction has expected value that's pretty much indistinguishable from minus infinity.
Global thermonuclear war? Oh sure it would kill some people but expected number of deaths and amount of suffering from let's say malaria or lack of access to fresh water in the next 100 years is far higher than expected death and suffering from a global thermonuclear war in the next 100 years.
Even our most recent total war, WW2, killed laughably small portion of the fighting population relative to historical norms. There's no reason to suspect WW3 would be any different, so number of deaths would most likely be rather limited. And as countries with low birth rates (that is pretty much all countries today) have historical record of trying very hard not to get into any war that could endanger their population (as opposed to send bombs to other countries and such), chance of such a war is tiny.
So let's say 1% chance of global thermonuclear war killing 100 million people in the next 100 years (expected 1 million deaths) versus 1 million deaths a year from malaria, and 2 from diarrhea. I think we have our priorities wrong if we care about global thermonuclear wars much.
(of course people might disagree with these estimates, in which case they would see a global thermonuclear war as more important issue than me)
Under those assumptions your estimates are sound, really. However, should we only count the direct deaths incurred as a consequence of a direct nuclear strike ? Or should we also take into account the nuclear fallout, radiations, nuclear winter, ecosystems crashing down, massive economy and infrastructure disruption, etc. ? How much more worse does it get if we take such considerations into account ?
Aside from those considerations, I really agree with your idea of getting our priorities right, based on numbers. That's exactly the reason why I'd advocate antiagathic research above a lot of other things, which actually kill and make less people suffer than aging itself does, but not everyone seems to agree to that.
The prospect of a dangerous collection of existential risks and risks of major civilizational-level catastrophes in the 21st century, combined with a distinct lack of agencies whose job it is to mitigate against such risks probably indicates that the world might be in something of an emergency at the moment. Firstly, what do we mean by risks? Well, Bostrom has a paper on existential risks, and he lists the following risks as being "most likely":
To which I would add various possibilities for major civilization-level disasters that aren't existential risks, such as milder versions of all of the above, or the following:
This collection is daunting, especially given that the human race doesn't have any official agency dedicated to mitigating risks to its own medium-long term survival. We face a long list of challenges, and we aren't even formally trying to mitigate many of them in advance, and in many past cases, mitigation of risks occurred on a last-minute, ad-hoc basis, such as individuals in the cold war making the decision not to initiate a nulcear exchange, particularly in the Cuban missile crisis.
So, a small group of people have realized that the likely outcome of a large and dangerous collection of risks combined with a haphazard, informal methodology for dealing with risks (driven by the efforts of individuals, charities and public opinion) is that one of these potential risks will actually be realized - killing many or all of us or radically reducing our quality of life. This coming disaster is ultimately not the result of any one particular risk, but the result of the lack of a powerful defence against risks.
One could argue that I [and Bostrom, Rees, etc] are blowing the issue out of proportion. We have survived so far, right? (Wrong, actually - anthropic considerations indicate that survival so far is not evidence that we will survive for a lot longer, and technological progress indicates that risks in the future are worse than risks in the past). Major civilizational disasters have already happened many, many times over.
Most ecosystems that ever existed were wiped out by natural means, almost all species that have ever existed have gone extinct, and without human intervention most existing ecosystems will probably be wiped out within a 100 million year timescale. Most civilizations that ever existed, collapsed. Some went really badly wrong, like communist Russia. Complex, homeostatic objects that don't have extremely effective self-preservation systems empirically tend to get wiped by the churning of the universe.
Our western civilization lacks an effective long-term (order of 50 years plus) self-preservation system. Hence we should reasonably expect to either build one, or get wiped out, because we observe that complex systems which seem similar to societies today - such as past societies - collapsed.
And even though our society does have short-term survival mechanisms such as governments and philanthropists, they often behave in superbly irrational, myopic or late-responding ways. It seems that the response to the global warming problem (late-responding, weak, still failing to overcome co-ordination problems) or the invasion of Iraq (plain irrational) are cases in point from recent history, and that there are numerous examples from the past, such as close calls in the cold war, and the spectacular chain of failures that led from world war I to world war II and the rise of Hitler.
This article could be summarized as follows:
The systems we have for preserving the values and existence of our western society, and the human race as a whole are weak, and the challenges of the 21st-22nd century seem likely to overwhelm them.
I originally wanted to write an article about ways to mitigate existential risks and major civilization-level catastrophes, but I decided to first establish that there are actually such things as serious existential risks and major civilization-level catastrophes, and that we haven't got them handled yet. My next post will be about ways to mitigate existential risks.