The Doomsday argument (DA) is a probabilistic argument that claims to predict the number of future members of the human species given an estimate of the total number of humans born so far. "If Leslie's figure is used, then 60 billion humans have been born so far, so it can be estimated that there is a 95% chance that the total number of humans N will be less than 20 × 60 billion = 1.2 trillion. Assuming that the world population stabilizes at 10 billion and a life expectancy of 80 years, it can be estimated that the remaining 1140 billion humans will be born in 9120 years" this is a complex theory, but basically, it gives a idea of how long we have left as a species. there is another theory stating we have closer to 7.8 million years, but i personally find that unrealistic.***“Doomsday Argument.” Wikipedia, Wikimedia Foundation, 2 May 2018, en.wikipedia.org/wiki/Doomsday_argument.
the article is based on a report of the topic. "'The substantial levels of investment in nuclear weapons and nuclear weapons systems and their modernization have enhanced rather than decreased the likelihood of an intentional or inadvertent detonation event.'" in a nutshell, the increase of relying on automated systems, take the Hawaii missile warning for instance, if a automated system would retaliate, but it ended up to be a false alarm, it would lead to a nuclear catastrophe. ***“UN Voices Fears of 'Catastrophic Nuclear Accident' as Global Tensions Increase.” CSGlobe, 22 Apr. 2017, csglobe.com/un-catastrophic-nuclear-accident/.
Achenbach stresses over the Yellowstone super volcano. " it's 44 miles across - and not until the 1980s did they grasp that this thing is fully alive and still threatens to erupt catastrophically. Yellowstone is capable of eruptions thousands of times more violent than the Mount St. Helens eruption of 1980. The northern Rockies would be buried in multiple feet of ash. Ash would rain on almost everyone in the United States" this may certainly be a immediate threat to the united states, especially everyone within a 500-600 mile radius. you can forget about global warming when the northern hemisphere (or more) is covered in ash, inducing global cooling. ***Achenbach, Joel. “The Yellowstone Supervolcano Is a Disaster Waiting to Happen.” Chicagotribune.com, Chicago Tribune, 21 Apr. 2018, www.chicagotribune.com/news/nationworld/science/ct-yellowstone-supervolcano-20180421-story.html.
Gamma-ray bursts are highly concentrated beams that shoot out of a super-nova, or hyper-nova. as kershiner said "If one of these jets of radiation hit Earth, it could destroy the entire ozone layer. Global cooling would occur..." but generally, a GRB hitting the earth happens roughly once every billion years. another factor is the accuracy of getting hit with one, imagine trying to hit a small marble from several hundred thousand kilometers away with a gun that shoots in any direction at random. unfortunately, "it might not be a comfort to know that some scientists posit that gamma rays might've played a part in the late Ordovician extinction about 440 million years ago [source: Melott]. About 70 percent of all marine life died -- and pretty much everything was marine back then" So the chance of the earth getting hit with one within the lifetime of humans is slim, but not impossible, and fortunately we have another 500 million years before we have to worry otherwise. ***Kershner, Kate. “Could a Gamma-Ray Burst Wipe out All Life on Earth?” HowStuffWorks Science, HowStuffWorks, 8 Mar. 2018, science.howstuffworks.com/gamma-ray-burst-life-earth.htm.