An existential risk is any risk that has the potential to eliminate all of humanity or, at the very least, kill large swaths of the global population, leaving the survivors without sufficient means to rebuild society to current standards of living.
Until relatively recently, most existential risks (and the less extreme version, known as global catastrophic risks) were natural, such as the supervolcanoes and asteroid impacts that led to mass extinctions millions of years ago. The technological advances of the last century, while responsible for great progress and achievements, have also opened us up to new existential risks.
Nuclear war was the first man-made global catastrophic risk, as a global war could kill a large percentage of the human population. As more research into nuclear threats was conducted, scientists realized that the resulting nuclear winter could be even deadlier than the war itself, potentially killing most people on earth.
Biotechnology and genetics often inspire as much fear as excitement, as people worry about the possibly negative effects of cloning, gene splicing, gene drives, and a host of other genetics-related advancements. While biotechnology provides incredible opportunity to save and improve lives, it also increases existential risks associated with manufactured pandemics and loss of genetic diversity.
Artificial intelligence (AI) has long been associated with science fiction, but it's a field that's made significant strides in recent years. As with biotechnology, there is great opportunity to improve lives with AI, but if the technology is not developed safely, there is also the chance that someone could accidentally or intentionally unleash an AI system that ultimately causes the elimination of humanity.
Climate change is a growing concern that people and governments around the world are trying to address. As the global average temperature rises, droughts, floods, extreme storms, and more could become the norm. The resulting food, water and housing shortages could trigger economic instabilities and war. While climate change itself is unlikely to be an existential risk, the havoc it wreaks could increase the likelihood of nuclear war, pandemics or other catastrophes.
During the early years of trains, many worried that the human body couldn't handle speeds greater than 30 miles per hour; people were hesitant to use the first phones for fear of electric shocks or that the devices were instruments of the devil himself; and there were equally dire predictions about planes, heart transplants and Y2K, just to name a few red herrings. While we hope that concerns about some of the technologies listed on this page will prove equally unwarranted, we can only ensure that to be the case with sufficient education, research and intervention. We humans should not ask what will happen in the future as if we were passive bystanders, when we in fact have the power to shape our own destiny.