How Long Would An Impact Winter Last (And Why)?

How Long Would An Impact Winter Last (And Why)?

Exact Answer: 6 Months to 25 Years

Impact winter is a hypothetical phenomenon that exists when a comet or an asteroid collides with the surface of the earth. It is hypothesized that this would cause extreme cold weather that can even lead to mass extinction. Some recent studies have been able to prove this hypothesis.

Impact winter is considered to be one of the possible reasons for the extinction of the dinosaurs. The drastic fall in the global temperature is due to the enormous amounts of debris ejected into the atmosphere. The debris blocks the light & heat received by the earth from the sun.

How Long Would An Impact Winter Last

How Long Would An Impact Winter Last?

The asteroid or the comet should be large, at least 4 to 5 kilometers in diameter. Moreover, the point of contact of these celestial bodies may also influence the impact winter. The duration of an impact winter is highly dependent upon the size of the celestial body and the impact of the celestial body on the earth’s surface. 

For example, it is presumed that a celestial body (most probably an asteroid) of a diameter of 10 meters hit the surface of the earth, which caused the mass extinction of the dinosaurs. There are estimations that the impact winter due to this asteroid collision lasted for at least 3 years. 

Few computer simulations have projected the duration of impact winter to be of 10 years. If we were to consider only the size of the asteroid to be the key factor and ignore other factors, then the impact winter duration can be estimated by using computer simulations.

The duration of the impact winter can be summarized as follows,

Size Of An AsteroidDuration of Impact Winter
5 Meters6 Months to 3 Years
7 Meters1 Year to 5 Years
10 Meters3 Years to 10 Years
15 Meters7 Years to 18 Years
20 Meters10 Years to 25 Years

Why Would An Impact Winter Last So Long?

When a celestial body of diameter above 4 or 5 kilometers hits the surface of the earth, it causes soil, dust, ash, and other particles to rise into the atmosphere. These particles block the light & absorb the heat that reaches the earth’s surface. 

The radiation of the sun that reaches the earth is essential for the photosynthesis reaction. This reaction is essential for plants to produce their food. Lack of sunlight will disrupt the food cycle. Subsequently, due to the lack of radiation heat, the temperature drops drastically.

Along with the impact winter, natural catastrophes like storms, hurricanes, tsunamis, and earthquakes may also get triggered. They not only cause large-scale destruction but add to the number of particles absorbing radiation heat. The large temperature differences between the atmosphere and water bodies would occur.


Gradually, as time progresses, the particles blockading sunlight & radiation heat will eventually fall to the earth’s surface. This would allow the radiation heat to warm the planet. This will again restore the temperature difference between atmosphere and water bodies. 

It takes time to end the above-mentioned cycle. The intensity of the impact winter in the initial few months is quite severe. After a year or two, the intensity reduces drastically. The end of impact winter can be marked by the restoration of global temperature back to normal.


Impact winter has the potential to wipe out the entire species. It is followed by a series of natural catastrophes that can destroy the earth. The duration of the impact winter is influenced by the size of the celestial body & the contact point of the earth’s surface. Lack of sunlight for photosynthesis, extremely cold weather, and catastrophes may wipe out at least 25 percent of the global species.

Impact winter may not last longer than a decade or two. Eventually, the global temperature will restore to normal. The conducive atmosphere of the earth will be restored. This would allow the remaining species to continue their life on the earth. The chances of an impact winter due to a celestial body are extremely rare.


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    1. Absolutely, understanding these processes is critical for preparing for potential future scenarios.

  1. This article provides a compelling overview of the potential impacts and duration of an impact winter.

  2. The duration of an impact winter, particularly for larger celestial bodies, could have severe implications on the planet.

  3. The potential for an impact winter and its duration definitely raises important questions about the future of our planet.

  4. The duration of an impact winter varies based on the size of the celestial body and other factors. A very informative article indeed.

    1. Yes, understanding these factors is crucial for assessing the risks and potential mitigating measures.

  5. The process of recovery from an impact winter is quite fascinating and highlights the resilience of life on Earth.

    1. Absolutely, the restoration of a conducive atmosphere and the potential for life to continue is a testament to the planet’s ability to recover.

  6. The threat of an impact winter is alarming! Even more worrisome is that it could last for such a long time.

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