Time is sometimes our friend and often our enemy.
Why think about existential risk at all? As an immortalist, this answer is simple. I plan to live forever, so any risk to life (in general and specifically) is going to have to be minimized, prepared for, and addressed.
Here are my notes on the subject, followed by a brainstorming with my wife to help identify risks.
1. Identify, categorize, and evaluate risks: develop a Threats To Life Catalog.
2. Quantify risks.
3. Develop a strategy for minimizing each risk.
4. Develop a mathematical model for evaluating the total risk level and the effects of our strategy against that risk.
5. Continuously monitor for new risks and reevaluate existing risks.
Develop a "risk pattern language" or template.
Risk name
category
description
sources
risk level
time frame
strategies: minimize, prepare, recover.
references
evaluations
We can consolidate sources of risk and develop an entry and strategy for each.
Source name
description
risks
strategy
references
evalutations
This will help us identify what tends to cause risk, and we can develop targetted strategies for making human life safer.
Here's a brainstorming of ideas, please feel free to contribute to the list, change categories, critique, or expand on individual items for the catalog. I would prefer to keep even seemingly weak possibilities in the catalog so they can be reevaluated from time to time.
Risks
Man vs. Nature
(Astral)
Stellar:
Rogue star passes through or near system
Sol:
Supernova
Burnout
Flareout/becomes irregular
Galactic:
Nearby intense gamma ray burst
Parallel Universe intersection or disaster (c.f. M-branes, gravity)
Universal/Cosmological:
Proton decay accelerates/other particulate inherent problem in matter.
Spacetime becomes irregular due to stress
Big Crunch occurs
Spontaneous quantum fluction results in radical expansion of local space
or other major distruption
"Laws" are part of a local bubble, which pops.
Planetary:
Lunar asteroid collision
Jupiter or other planetary body disintegrates, littering solar system
Large Asteroid or Comet Impact causes huge explosion
Massive increase in space debris cause many small impacts
Comet or asteroid brings template chemical or large doses of hazardous material
alien invasion/assault
Permanent major environmental change or disruption caused by:
supervolcanic eruption c.f. supervolcanoes
massive methane release and ignition
global warming / water temperature change
environmental/ecological systemic failure
- genetic engineering of food sources
"natural" disease
- ebola, marburg, etc. run rampant
Evolutionary quick genetic change causes nonintelligent humans to predominate.
Simulation Shutdown: existence is some form of simulation for which there are outside controls, and the experiment is terminated.
Man vs. Man: War
global thermonuclear war - direct and environmental harm
conventional war
biological warfare : Artificial Disease - super bio strains
chemical or radiological warfare: distributed release of fine plutonium
nanotech plagues/weapons
Man vs. Man: Accident
Gray Goo - nanoplagues
physics experiment disaster: accidental creation of template particle or black hole, etc.
development of hostile artificial superintelligence
Memetics:
Massive memetic failure or assault
Voluntary Human Extinction Movement or equivalent; apocalypse cult.
ALF, ELF, GLF, Church of Euthanasia.
The Joke That Kills
Apathy
Coincidence: everyone gets accidentally killed at approximately the same time.
Gradual Decay and slow extinction
Well, it's a start.
Patrick