A new study suggests that a collision with a medium-sized asteroid can drastically change the Earth’s climate over several years and make life difficult for people all over the planet.
Among other effects, such an impact on the land (as opposed to the sea) can lead to the fact that average global temperatures will drop to the level of the ice age, which will lead to a sharp decrease in precipitation and productivity of plants, the researchers note.
“These will be very unpleasant times,” said Charles Bardin of the National Center for Atmospheric Research in Boulder, Colorado, in December during a presentation at the annual autumn meeting of the American Geographical Union (AGU) in San Francisco.
Short-term climate change
Bardin and his colleagues modeled what would happen to the Earth’s climate if a space rock 0.6 miles (1 km) wide crashes into one of the land parts of the planet. Such an impact is likely to create a 9-mile (15 km) crater, lift huge amounts of dust into the atmosphere and trigger large-scale fires that would lift a lot of soot into the air, provided that the collision did not occur in a desert area with little vegetation, - said Bardeen.
The material lifted after this hypothetical fall of the asteroid would remain in the atmosphere for a long time — about 6 years in the case of dust and 10 years for soot. These are the worst results that researchers have put forward (which also include the widespread occurrence of fires). These particles will heat up on the Sun, warming the stratosphere and significantly speeding up chemical reactions that destroy ozone, protecting the Earth from harmful ultraviolet (UV) radiation. Indeed, the level of atmospheric ozone will be temporarily reduced by 55%, with the result that the UV index of the surface will increase to 30 over several years. (According to the US Environmental Protection Agency, UV index 11 or higher means “extreme risk of harm from unprotected exposure to the Sun”).
Bardeen believes that atmospheric soot and dust will also help reduce the amount of sunlight falling on Earth to 70% in the first year or two. As a result, the average global surface temperature will cool by 14.5 degrees Fahrenheit (8 degrees Celsius), “which is roughly equivalent to the Ice Age situation,” said Bardin during his presentation at the American Geographical Union.
He added that the main part of this temperature difference will occur on Earth. But the effects will also be felt in the oceans, and the sea ice cover will constantly increase. Since water has high thermal inertia, changes in ocean temperature will continue for a relatively long time. For example, the models made by the team assume that the upper layers of the ocean will still be 0.9 degrees Fahrenheit (0.5 degrees Celsius) cooler than the standard temperature 15 years after the impact of the asteroid.
Global cooling will also lead to a 50% fall in precipitation worldwide, ”Bardin said.
“This is due to a lost source of heat and a decrease in temperature, so we lose convection; we no longer have sources, ”he said. A decrease in sunlight, rain and snow will result in a fall of about 50% in the productivity of all plants, and this is not very good news for farmers and people dependent on them (which all people in the world belong to). Bardeen believes that crops in North America, Europe and North Asia would be particularly hard hit. While agricultural land in India, South America and Africa will survive this better.
Thus, the picture is not very comforting. The impact of such an asteroid can cause “a very heavy global impact” in a few years, said Bardin.
But he added that in order to lead to mass extinction, the space object should be about 10 times larger than that described above. (The asteroid, which is believed to have destroyed dinosaurs and other species 65 million years ago was probably about 6 miles or 10 km wide.)
Ocean Influence?
Bardin and his team modeled the consequences of a collision with an asteroid on land. But it is more likely that the space stone will collide with water. After all, the oceans occupy about 70% of the earth's surface. What will happen then?
In 2010, this scenario was modeled and considered by the late Elizabeth Pierazzo. As a result, it was found that the situation for the protective ozone layer of the Earth will be dramatic.
A 0.6-mile-wide asteroid falling into the ocean will be enough to create saline water vapor that will destroy a huge amount of ozone. As a result, the UV surface index will rise to 56. Such high levels of radiation that have never been experienced in the history of mankind are likely to make people breathe fire. But getting into the ocean will not have such climatic consequences as in the variant of a collision with the earth, ”added Bardin.
“Temperature effects, precipitation effects, effects on plants - all this concerns only the option of an asteroid falling on the land,” he said.
However, the chances of an asteroid collision and global serious consequences seem far away, at least in the near future.
To date, astronomers have noticed 879 near-Earth asteroids, which are at least 0.6 miles wide, and none of them represent an immediate threat. The finished models suggest that these 879 asteroids represent more than 90% of the total number of representatives of the cosmic “rocks” in the region of the Earth, NASA officials said.
If the asteroid is in dangerous proximity to the Earth, then humanity should not be idle, waiting for the inevitable end. If a space object is detected with sufficient time - ideally 10 years or more - then you can have time to develop and use a special automatic spacecraft that crashes into the object and pushes it aside.
The destruction of the object by a nuclear bomb is also an option considered by researchers. Especially this option is suitable if the object is too large or seen too late.
