"Nuclear winter," or as it was initially termed, "nuclear twilight," began to be considered as a scientific concept in the 1980s, after it became clear that an earlier hypothesis, that fireball generated NOx emissions would devastate the ozone layer, was losing credibility. It was within this context that the climatic effects of soot from fires was "chanced upon" and soon became the new focus of the climatic effects of nuclear war. In these model scenarios, various soot clouds containing uncertain quantities of soot were assumed to form over cities, oil refineries, and more rural missile silos. Once the quantity of soot is decided upon by the researchers, the climate effects of these soot clouds are then modeled. The term "nuclear winter" was a neologism coined in 1983 by Richard P. Turco in reference to a 1-dimensional computer model created to examine the "nuclear twilight" idea, this 1-D model output the finding that massive quantities of soot and smoke would remain aloft in the air for on the order of years, causing a severe planet-wide drop in temperature. Turco would later distance himself from these extreme 1-D conclusions.
After the failure of the predictions on the effects of the 1991 Kuwait oil fires, that were made by the primary team of climatologists that advocate the hypothesis, over a decade passed without any new published papers on the topic. More recently, the same team of prominent modellers from the 1980s have begun again to publish the outputs of computer models, these newer models produce the same general findings as their old ones, that the ignition of 100 firestorms, each comparable in intensity to that observed in Hiroshima in 1945, could produce a "small" nuclear winter. These firestorms would result in the injection of soot (specifically black carbon) into the Earth's stratosphere, producing an anti-greenhouse effect that would lower the Earth's surface temperature. The severity of this cooling in Alan Robock's model suggests that the cumulative products of 100 of these firestorms could cool the global climate by approximately 1 °C (1.8 °F), largely eliminating the magnitude of anthropogenic global warming for two to three years. Robock has not modeled this, but has speculated that it would have global agricultural losses as a consequence.
As nuclear devices need not be detonated to ignite a firestorm, the term "nuclear winter" is something of a misnomer. The majority of papers published on the subject state that without qualitative justification, nuclear explosions are the cause of the modeled firestorm effects. The only phenomenon that is modeled by computer in the nuclear winter papers is the climate forcing agent of firestorm-soot, a product which can be ignited and formed by a myriad of means. Although rarely discussed, the proponents of the hypothesis state that the same "nuclear winter" effect would occur if 100 conventional firestorms were ignited.
A much larger number of firestorms, in the thousands,airbursting nuclear weapon use during an American-Soviet total war. This larger number of firestorms, which are not in themselves modeled, are presented as causing nuclear winter conditions as a result of the smoke inputted into various climate models, with the depths of severe cooling lasting for as long as a decade. During this period, summer drops in average temperature could be up to 20 °C (36 °F) in core agricultural regions of the US, Europe, and China, and as much as 35 °C (63 °F) in Russia. This cooling would be produced due to a 99% reduction in the natural solar radiation reaching the surface of the planet in the first few years, gradually clearing over the course of several decades.
was the initial assumption of the computer modelers who coined the term in the 1980s. These were speculated to be a possible result of any large scale employment of counter-value
On the fundamental level, since the advent of photographic evidence of tall clouds were captured, it was known that firestorms could inject soot smoke/aerosols into the stratosphere but the longevity of this slew of aerosols was a major unknown. Independent of the team that continue to publish theoretical models on nuclear winter, in 2006, Mike Fromm of the Naval Research Laboratory, experimentally found that each natural occurrence of a massive wildfire firestorm, much larger than that observed at Hiroshima, can produce minor "nuclear winter" effects, with short-lived, approximately one month of a nearly immeasurable drop in surface temperatures, confined to the hemisphere that they burned in. This is somewhat analogous to the frequent volcanic eruptions that inject sulfates into the stratosphere and thereby produce minor, even negligible, volcanic winter effects.
A suite of satellite and aircraft-based firestorm-soot-monitoring instruments are at the forefront of attempts to accurately determine the lifespan, quantity, injection height, and optical properties of this smoke. Information regarding all of these properties is necessary to truly ascertain the length and severity of the cooling effect of firestorms, independent of the nuclear winter computer model projections.
Presently, from satellite tracking data, stratospheric smoke aerosols dissipate in a time span under approximately two months. The existence of any hint of a tipping point into a new stratospheric condition where the aerosols would not be removed within this time frame remains to be determined.