Nuclear darkness refers to a predicted darkening of the Earth caused by the massive absorption of sunlight by a global stratospheric

Stratosphere

The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...

 smoke layer created by the burning of cities and industrial areas following a nuclear conflict. Nuclear darkness resulting from a large nuclear exchange can produce a Nuclear winter

Nuclear winter

Nuclear winter is a predicted climatic effect of nuclear war. It has been theorized that severely cold weather and reduced sunlight for a period of months or even years could be caused by detonating large numbers of nuclear weapons, especially over flammable targets such as cities, where large...

 effect, but nuclear darkness from much smaller nuclear conflicts, that do not produce the temperatures or conditions associated with nuclear winter, will still have catastrophic effects on global climate.

Research

New research indicates that much less than one percent of the current explosive power of the global nuclear arsenal, if detonated in cities of the sub-tropics, would put up to 5 million tonnes of smoke into the stratosphere, where it would reside for many years. Smoke from a regional nuclear conflict would block enough sunlight to drop average surface temperatures on Earth to pre-industrial levels, significantly shorten growing season

Growing season

In botany, horticulture, and agriculture the growing season is the period of each year when native plants and ornamental plants grow; and when crops can be grown....

s, and cause catastrophic disruptions of the global climate

Climate

Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

, as well as massive destruction of the ozone layer

Ozone layer

The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth...

.