WEFOUNDnear earth objects animation

Near Earth Objects are asteroids or comets that have orbits around the Sun that bring them close to the Earth. The actual definition of an NEO is a comet or asteroid whose orbit brings it close to Earth’s orbit. The criterion is a perihelion distance < 1.3 AU.

However, the main killing mechanism will be the vast amount of dust and debris injected into the upper atmosphere, combined with the smoke from the firestorms (witness recent events in Indonesia). These will obscure the Sun and cause a phenomenon similar to, but much more severe than the “nuclear winter” that became such an issue during the Cold War. It is this that is likely to pose the greatest threat to the ecosphere on a global scale as food chains collapse and darkness, cold and starvation set in.

After a few months or years the atmosphere will clear, but the surface of the Earth, now mainly white in colour, might reflect too much of the Sun’s radiation to prevent a new ice age. However, there are other mechanisms at work. The atmosphere will contain a substantial excess of CO2, resulting from the global fires, the release of the gas from carbonate rocks and volcanism. The Earth could be in for a massive overdose of greenhouse effect. The balance between sweltering and freezing is a very fine one. Such globally threatening events can be expected on time scales of 100,000 years.