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The running theory is that if the Earth is hit by a sufficiently large meteor, that the impact would create an ice age from all the dust it would put into the atmosphere. While this has been historically seen as a bad thing, this has me wondering if people might one day want to intentionally steer a large asteroid or comet at the Earth as a way to combat global warming.

Could such an impact permanently (or semi-permanently) reverse global warming without causing so much secondary environmental damage that it would make the outcome worse than letting global warming take its course?

You don't need a meteor to lower temperatures

I want to introduce you to the year 1816. Also known as the year without a summer. In short, there was a volcanic eruption which expelled a lot of sulfite dioxide particles in the atmosphere. These particles reflected part of the light that came to Earth, thus cooling areas underneath. Areas that covered large parts of the northern hemisphere.

However, that's not good

The "without a summer" part of the name is not at all coincidental. And it's putting the effects mildly. It doesn't just mean that you skipped going to the beach this year. Effects included:

• snow in the month of July


• frost and low temperatures led to a lot of crop failures


• people lost a lot of money, especially those who were doing agriculture but sectors suffered as well


• people starved to death because of the weak or non-existent harvest


• other people froze to death because they weren't prepared to warm their homes in the summer

Another name for 1816 is "eighteen hundred and froze to death". That better helps convey just how bad "no summer" can be.

Undirected changes are not good

The global average temperatures in 1816 fell by only something in the region of 0.5° C (0.9° F). It's a relatively minor change when you look at the numbers, yet the effects were catastrophic. That was not directed in any way.

A meteor hitting Earth to try and plunge the global temperatures down would lead to an even bigger catastrophe. It would have even less of a direction in terms of effects. In addition to the temperature change, you'd have the impact to deal with which can wreak all sorts of havoc. It depends on what the meteor is, how big it is, where it falls, etc. All things you can hardly account for. I doubt you can even account for what temperature shift you'd get from it.

All in all, if we can't even manage when only the temperature changed alone, I don't see how dropping a big rock from the sky and hoping for the best would work out.

But maybe you can direct the change

Thanks to 1816 and science, we now know a lot more about what particles can do in the atmosphere. If you have some way of introducing more sulfite dioxide particles at a very tightly controlled rate, you can cool the planet. If you can somehow get rid of them, you can warm it back up. So, you might be able to beat greenhouse gases by bypassing the problem entirely. In effect, you will have a "thermostat" for the entire planet and even though greenhouse gasses retain heat, you can set the "thermostat" slightly lower to compensate for that. And then turn it back up before it starts snowing in July.

That is likely to be a huge effort. I don't even know if we have an idea what technology is needed to achieve that. Moreover, it doesn't really solve the core issue - that would still be there. However, a civilisation advanced enough to be able to direct a meteor down to their own planet, and crazy enough to actually do it, could probably go with a "global thermostat" instead. It's still better than their other plan.

You're trying to cure the sickness by alleviating a symptom.

You can't cure global warming by putting more pollution into the air. You may temporarily bring the patient's temperature down, but humanity will respond by turning up the heat. In the end, you'll make global warming much, much worse.

Please keep in mind that global-warming/climate-change/name-d'jour is a technological problem. Humanity industrialized. The act of industrialization is having a complex effect on our world and one symptom of that effect is the planet getting warmer.

Another symptom of that effect is my respiratory distress due to pollution. Not surprisingly, you can't solve the problem of pollution by making me wear a surgical mask all the time, either.

Yes, you can force the world to cool down by dropping a meteor on it.

You can also do it by detonating enough nuclear bombs. Both alleviations of the symptom are temporary. Once the material thrown into the sky settles, you're worse off than you were before because not only did you fail to fix the technological problem, you created greater dependency on the technology for humanity to survive the effects of dropping a big rock on the planet or blowing up a bunch of nukes.

And that's not even accounting for the damage you'd cause by dropping a big rock on the planet. Think "Tunguska blast" a thousand times over.

There are really only two ways to fix the human contribution to global warming:

1. Stop using the technology (hah!)




2. Improve the technology so that it has a lower impact.

Most activists work toward #1 with completely predictable results (it doesn't work). The rest of us (well, some of the rest of us, there are many who don't care) are working toward #2 as quickly as we can.

It would be much, much worse than anything climate change does to us. Any impact large enough to create a global cooling effect would cause catastrophic damage over a huge area, kill a ton of people outright, and cause unpredictable changes to nearly every climate.

It would take an immense amount of effort to steer the asteroid into us, and would only ADD energy to our planetary system. A lot of energy.

We would be MUCH better mining an asteroid for metals and making an orbiting field of reflectors to limit the sunlight reaching Earth.

I'm going the misanthropist way here: you can, by killing most humans and civilisation.

If you throw a lot of tiny meteor (big enough to go through the atmoshpere and still exist) during a long period (a few days).
By removing (most of) humanity/civilisation, you'll surely stop man-made climate change.

However, this doesn't go without affecting the environment:

• You'll also destroy flora/fauna with the meteors.


• Some infrastructures are dangerous to destroy (nuclear power plants).


• Letting civilisation unsupervised might (will) cause additional damages (dams will break, spontaneous explosions cause wild fires).

Note that humanity doesn't cover a big % of earth; you'll either need to aim your meteors on cities, or randomly cover a lot places (which will surely have more impact on environment than letting global warming continue).

A solid yes, but...

In theory, a sufficiently large meteor would throw up enough dust to cause a significant effect on the climate. Science has studied enough vulcano eruptions (e.g. the Pinatubo, Philippines, in 1991) to understand and measure the effects and make a reasonable prediction that yes, this approach would cause a cooling effect.

Now for the but (and in the words of Ben Goldacre: It's a big but):
There is no way to estimate the precise size of meteor you need to throw up the precise amount of dust in the precise way (and height) needed, nor steer it to a precise enough impact location to make a prediction even reasonably appropriate. You could easily hit something you don't want to hit. Either a city, or arable land, or the ocean (causing a floodwave). With the size of meteor required, you could easily do massive damage or cause chain-reactions that dwarf the effect of your meteor.

You also would have no guarantee that you're not doing either not enough cooling to make the whole thing worth it, or are overdoing it and cause a lot more cooling than you wanted and then you'll do what, exactly?