User:Nookular/Nuclear winter

Effects on agriculture and fishery
Life is fragile when reacting to even the smallest environmental changes such as a few degrees of temperature rise, decrease in precipitation, or even terrain changes. Nuclear bomb detonation will not only bring a series of changes to our climate and atmosphere, but also destruction of massive scale. The areas close to the center of blast will be contaminated by high concentration of radiation for hundreds of years leading to global radioactive fallout, and all the organisms in that radius will die or suffer major genetic damage and mutation. The firestorm produced from either airburst or surface burst nuclear bomb can easily burndown cities and forests, making the Earth's soil inhabitable within a few days. The fine dust raised by surface burst nuclear weapons and the smoke generated from burning cities and forests will cover the Earth's atmosphere within 2 weeks, blocking most if not all the sunlight. Due to the lack of sunlight, the surface temperature on Earth will decrease rapidly, followed by heavy snowfalls. Despite the absence of sunlight and severe weather, an ice age is is unlikely to be triggered by a nuclear war because the rapid cooling period of 1 year predicted by models is likely too short to change the Earth's climate system and overcome the ocean heat reservoir.

After a simulated regional nuclear war between India and Pakistan, a catastrophic destruction of human civilization will probably not happen as portrayed in movies, but the the global climate will change due to the large amount of Carbon Dioxide produced from the firestorms and fallout clouds blocking the sunlight. The global temperature will decrease by 1°C - 2°C for 10 years, precipitation and solar radiation will also be affected. A study done in China, the largest grain producer in the world, showed that a colder, darker, and drier environment has detrimental effects on the crops yield: 30 megaton (29%) decrease of annual rice production, 36 megaton (20%) decrease of annual maize production, and 23 megaton (53%) of annual wheat production in the first year after the war. In the subsequent 5 to 10 years, the production of food will recover by 5% - 10%, but still much less than before the war. This study is conducted based on the simulation of a regional nuclear war, a global nuclear war will have a much greater effect on the food production around the world.

The marine life can also be easily affected by environmental changes such as temperature and sunlight. Next to agriculture, fishery is another major source of food for human, as it provides significant protein and nutrients in our everyday diet. In a 2020 study, a simulation was conducted to measure the biomass and catch of wild fish after a US-Russia nuclear exchange. The global cooling and reduced sunlight is expected to have many negative effects on ocean biomass and fishery, as they fall 18 $$\pm$$ 3% and 29 $$\pm$$ 7% in the next 10 years, respectively.

Recent modeling[edit]
Between 1990 and 2003, commentators noted that no peer-reviewed papers on "nuclear winter" were published.

Based on new work published in 2007 and 2008 by some of the authors of the original studies, several new hypotheses have been put forth, primarily the assessment that as few as 100 firestorms would result in a nuclear winter. However, far from the hypothesis being "new", it drew the same conclusion as earlier 1980s models, which similarly regarded 100 or so city firestorms as a threat.

Compared to climate change for the past millennium, even the smallest exchange modeled would plunge the planet into temperatures colder than the Little Ice Age (the period of history between approximately 1600 and 1850 AD). This would take effect instantly, and agriculture would be severely threatened. Larger amounts of smoke would produce larger climate changes, making agriculture impossible for years. In both cases, new climate model simulations show that the effects would last for more than a decade.

2007 study on global nuclear war[edit]
A study published in the Journal of Geophysical Research in July 2007, titled "Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences", used current climate models to look at the consequences of a global nuclear war involving most or all of the world's current nuclear arsenals (which the authors judged to be one similar to the size of the world's arsenals twenty years earlier). The authors used a global circulation model, ModelE from the NASA Goddard Institute for Space Studies, which they noted "has been tested extensively in global warming experiments and to examine the effects of volcanic eruptions on climate." The model was used to investigate the effects of a war involving the entire current global nuclear arsenal, projected to release about 150 Tg of smoke into the atmosphere, as well as a war involving about one third of the current nuclear arsenal, projected to release about 50 Tg of smoke. In the 150 Tg case they found that:"A global average surface cooling of −7 °C to −8 °C persists for years, and after a decade the cooling is still −4 °C (Fig. 2). Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about −5 °C, this would be a climate change unprecedented in speed and amplitude in the history of the human race. The temperature changes are largest over land … Cooling of more than −20 °C occurs over large areas of North America and of more than −30 °C over much of Eurasia, including all agricultural regions."In addition, they found that this cooling caused a weakening of the global hydrological cycle, reducing global precipitation by about 45%. As for the 50 Tg case involving one third of current nuclear arsenals, they said that the simulation "produced climate responses very similar to those for the 150 Tg case, but with about half the amplitude," but that "the time scale of response is about the same." They did not discuss the implications for agriculture in depth, but noted that a 1986 study which assumed no food production for a year projected that "most of the people on the planet would run out of food and starve to death by then" and commented that their own results show that, "This period of no food production needs to be extended by many years, making the impacts of nuclear winter even worse than previously thought."

2014[edit]
In 2014, Michael J. Mills (at the US National Center for Atmospheric Research, NCAR), et al., published "Multi-decadal global cooling and unprecedented ozone loss following a regional nuclear conflict" in the journal Earth's Future. The authors used computational models developed by NCAR to simulate the climatic effects of a soot cloud that they suggest would be a result of a regional nuclear war in which 100 "small" (15 Kt) weapons are detonated over cities. The model had outputs, due to the interaction of the soot cloud:"global ozone losses of 20–50% over populated areas, levels unprecedented in human history, would accompany the coldest average surface temperatures in the last 1000 years. We calculate summer enhancements in UV indices of 30–80% over Mid-Latitudes, suggesting widespread damage to human health, agriculture, and terrestrial and aquatic ecosystems. Killing frosts would reduce growing seasons by 10–40 days per year for 5 years. Surface temperatures would be reduced for more than 25 years, due to thermal inertia and albedo effects in the ocean and expanded sea ice. The combined cooling and enhanced UV would put significant pressures on global food supplies and could trigger a global nuclear famine."

2018[edit]
Research published in the peer-reviewed journal Safety suggested that no nation should possess more than 100 nuclear warheads because of the blowback effect on the aggressor nation's own population because of "nuclear autumn".

2019
2019 saw the publication of two studies on nuclear winter that build on previous modeling and describe new scenarios of nuclear winter from smaller exchanges of nuclear weapons than have been previously simulated.

As in the 2007 study by Robock ''et. al, a 2019 study by Coupe et. al'' models a scenario in which 150 Tg of black carbon is released into the atmosphere following an exchange of nuclear weapons between the United States in Russia where both countries use all of the nuclear weapons treaties permit them to. This amount of black carbon far exceeds that which has been emitted in the atmosphere by all volcanic eruptions in the past 1200 years but is less than the asteroid impact which caused a mass extinction event 66 million years ago. Coupe ''et. al used the "whole atmosphere community climate model version 4" (WACCM4), which has a higher resolution and is more effective at simulating aerosols and stratospheric chemistry than the ModelE simulation used by Rocock et. al''.

The WACCM4 model simulates that black carbon molecules increase to ten times their normal size when they reach the stratosphere. ModelE did not account for this effect. This difference in black carbon particle size results in a greater optical depth in the WACCM4 model across the world for the first two years after the initial injection due to greater absorption of sunlight in the stratosphere. This will have the effect of increasing stratospheric temperatures by 100K and result in ozone depletion that is slightly greater than ModelE predicted. Another consequence of the larger particle size is accelerating the rate at which black carbon molecules fall out of the atmosphere; after ten years from the injection of black carbon into the atmosphere, WACCM4 predicts 2 Tg will remain, while ModelE predicted 19 Tg.

The 2019 model and the 2007 model both predict significant temperature decreases across the globe, however the increased resolution and particle simulation in 2019 predict a greater temperature anomaly in the first six years after injection but a faster return to normal temperatures. Between a few months after the injection to the sixth year of anomaly, the WACCM4 predicts cooler global temperatures than ModelE, with temperatures more than 20K below normal leading to freezing temperatures during the summer months over much of the northern hemisphere leading to a 90% reduction in agricultural growing seasons in the midlatitudes, including the midwestern United States. WACCM4 simulations also predict a 58% reduction in global annual precipitation from normal levels in years three and four after injection, a 10% higher reduction than predicted in ModelE.

Toon ''et. al'' simulated a nuclear scenario in 2025 where India and Pakistan engage in a nuclear exchange in which 100 urban areas in Pakistan and 150 urban areas in India are attacked with nuclear weapons ranging from 15 kt to 100 kt and examined the effects of black carbon released into the atmosphere from airburst-only detonations. The researchers modeled the atmospheric effects if all weapons were 15 kt, 50 kt, and 100 kt, providing a range where a nuclear exchange would likely fall into given the recent nuclear tests performed by both nations. The ranges provided are large because neither India or Pakistan is obligated to provide information on their nuclear arsenals, so their extent remains largely unknown.

Toon ''et. al'' assume that either a firestorm or conflagration will occur after each detonation of the weapons, and the amount of black carbon inserted into the atmosphere from the two outcomes will be equivalent and of a profound extent; in Hiroshima in 1945, it is predicted that the firestorm released 1000 times more energy than was released during the nuclear explosion. Such a large area being burned would release large amounts of black carbon into the atmosphere. The amount released ranges from 16.1 Tg if all weapons were 15 kt or less to 36.6 Tg for all 100 kt weapons. For the 15 kt and 100kt range of weapons, the researchers modeled global precipitation reductions of 15% to 30%, temperature reductions between 4K and 8K, and ocean temperature decreases of 1K to 3K. If all weapons used were 50 kt or more, Hadley cell circulation would be disrupted and cause a 50% decrease in precipitation in the American midwest. Net primary productivity (NPP) for oceans decreases from 10% to 20% for the 15 kt and 100 kt scenarios, respectively, while land NPP decreases between 15% and 30%; particularly affected are midlatitude agricultural regions in the United States and Europe, experiencing 25-50% reductions in NPP. As predicted by other literature, once the black carbon is removed from the atmosphere after ten years, temperatures and NPP will return to normal.