Throughout history, humans have regularly wondered if there was going to be an end to life on earth as we know it. Recently, those fears seem more possible than ever. As scientists are learning more about the world we live in, they’re also learning more about what could go dramatically wrong. Below is a short list of major apocalyptic events that could happen in the next century or so.

Arctic glaciers are melting

Scientists have shown that the earth is steadily growing warmer due to climate change. In fact, NOAA and NASA have jointly reported that the last five years on earth have been some of the warmest in recorded history. Warmer temperatures mean more glacier melt which adds more water into the ocean and causes rising sea levels. This can also cause general flooding, increasingly intense hurricanes (which also bring flooding), and can change the intensity and seasonal timing of snowfalls and blizzards. Conversely, global temperature increases and altered weather patterns sometimes mean less precipitation in certain places and devastating wildfires. As if this wasn’t bad enough, climate change means that both wildlife and humans are affected by a loss of habitat, areas to grow food, and changed hunting grounds. None of this is good news for life on the planet.

Diseases are roaring back to life

Warmer temperatures on earth are also causing previously frozen areas of the earth are thawing. With this melt, diseases that have long been frozen and contained, become melted and alive again. That means that they’re able to affect humans and animals who have lost their immunity to the diseases over centuries. This has been the case for an Anthrax outbreak that affected Siberia in 2016 and 2017. More than 250,000 reindeer had to be culled in order to contain the disease but that wasn’t quite enough to prevent human contamination. The outbreak killed one human and made several others sick.

In addition to diseases becoming newly present due to thawing areas of the planet, they can impact humans in other ways. As humans become exposed to antibiotics through medical treatment and through the food supply, the antibiotics become less and less effective and resistant diseases which once could have been treated, become unexpectedly fatal. In addition, with increased ease in traveling around the globe, diseases which would previously have been contained to a single geography can spread. A worst-case scenario—a pandemic—becomes more possible.

A deadly asteroid or comet strike is possible

Unfortunately, an apocalyptic asteroid or comet strike isn’t just the stuff of blockbuster movies. In fact, it is likely that a massively destructive strike has already happened to our planet once, 65 million years ago, and caused the extinction of the dinosaurs. In the past century or so, comets have struck areas in Northern Russia, one which was captured on film and the other not directly seen but was detected by scientists after the fact. The largest meteor strike in recent history took place in Siberia in 1908. Called the Tunguska Event, it destroyed more than 80 million trees over an area approximating 2,000 miles. Thousands of people observed the effects of the event describing a fireball in the sky, a shaking of the ground, and explosive sounds.

While it would be difficult, if not impossible, to change the oncoming past of a comet or meteor, scientists are carefully tracking space objects so that the would have as much warning as possible if something was going to impact our planet. To date, they are tracking 867 objects, one of which could collide with Earth as soon as September 2019. Luckily, at this point, the objects being tracked are likely to burn up in earth’s atmosphere or become much less dangerous. However, as the strikes in the last century have shown, even small to moderate objects can cause a great deal of destruction.