Current studies
Nuclear winter revisited with a modern climate model and current nuclear arsenals; still catastrophic consequences by Alan Robock, Luke Oman et al., 2007
Previous studies can be summerized by a table below.
Compared to previous model simulations, relatively recent climate model simulation in 2007 was conducted with a state-of-the-art general circulation model, ModelE from the National Aeronautics and Space Administration Goddard Institute for Space Studies, which includes a module to calculate the transport and removal of aerosol particles. The atmospheric model is connected to a full ocean general circulation model with calculated sea ice, thus allowing the ocean to respond quickly at the surface and on yearly time scales in the deeper ocean. As seen in the bottom of the table, the simulation was run at 4ºX5º latitude-longitude resolution, with 23 vertical layers extending to a model top of 80km.
The simulation in 2007 was conducted twice for a long time-period, 10 years, one with 150Tg of smoke and one with 50Tg of smoke, injected into the upper troposphere(300-150mb) over a one-week period starting on May 15 spread over all the grid boxes over the 48 United States and over Russia. In addition, a 30-year control was conducted with no smoke aerosols.
The simulation in 2007 was conducted twice for a long time-period, 10 years, one with 150Tg of smoke and one with 50Tg of smoke, injected into the upper troposphere(300-150mb) over a one-week period starting on May 15 spread over all the grid boxes over the 48 United States and over Russia. In addition, a 30-year control was conducted with no smoke aerosols.
Results for the 150Tg case
The black carbon particles in the aerosol layer for the 150Tg case are heated by absorption of shortwave radiation and lofted into the upper stratosphere. The aerosols quickly spread globally and produce a long-lasting climate forcing [Fig. 2]. They end up much higher than is typical of weakly absorbing volcanic sulfate aerosols, which typically are just above the tropopause. As a result, the soot aerosols have a very long residence time and continue to affct surface climate fr more than a decade. The mass e-folding time* for the smoke is 4.6 yr, as compared to 1 yr for typical volcanic eruptions and 1 week for tropospheric aerosols. After 4.6 yr, the e-folding time is reduced, but is still longer than that of volcanic aerosols. In addition to the lofting of the smoke by solar absorption, another reason for this difference is that volcanic sulfte aerosols are larger, with an effective radius of 0.5μm, and thus they have a higher settling velocity than the smaller smoke aerosols.
e-foldingtime* - the time interval in which an exponentially growing quantity increases by a factor of e; it is the base-e analog of doubling time
e-foldingtime* - the time interval in which an exponentially growing quantity increases by a factor of e; it is the base-e analog of doubling time
[Fig 3] Change of global average surface air temperature, [Fig 4] Surface air temperature changes fr the 150 Tg case averaged for June, July, and August
precipitation, and net downward shortwave radiation of the year of smoke injection (Year0) and the next year (Year 1)
for the 5 Tg, 50 Tg and 150 Tg cases.
The maximum change in net global-average surface shortwave radiation for the 150Tg case is -100Wm-2 even 10 years after the initial smoke injection. This forcing greatly exceeds the maximum global-average surface forcing of -4Wm-2 for the 1991 Mt. Pinatubo volcanic eruption, the largest of the 20th century. [Fig 3] The effects of the smoke cloud on surface temperature are extremely large. A global average surface cooling of-7ºC to -8ºC persists for years, and after a decade the cooling is still -4ºC. Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about -5ºC, this would be climate change unprecedented in speed and amplitude in the history of the human race.
The temperature changes are largest over land due to its low heat capacity, but there is substantial cooling over oceans, too. [Fig 4]Cooling of more than -20ºC occurs over large areas of North America and of more than -30ºC over much of Eurasia. There are also large temperature changes in the tropics and over Southern Hemisphere continents. Large climatic effects would occur in regions far removed from the target areas or the countries involved in the conflict.
precipitation, and net downward shortwave radiation of the year of smoke injection (Year0) and the next year (Year 1)
for the 5 Tg, 50 Tg and 150 Tg cases.
The maximum change in net global-average surface shortwave radiation for the 150Tg case is -100Wm-2 even 10 years after the initial smoke injection. This forcing greatly exceeds the maximum global-average surface forcing of -4Wm-2 for the 1991 Mt. Pinatubo volcanic eruption, the largest of the 20th century. [Fig 3] The effects of the smoke cloud on surface temperature are extremely large. A global average surface cooling of-7ºC to -8ºC persists for years, and after a decade the cooling is still -4ºC. Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about -5ºC, this would be climate change unprecedented in speed and amplitude in the history of the human race.
The temperature changes are largest over land due to its low heat capacity, but there is substantial cooling over oceans, too. [Fig 4]Cooling of more than -20ºC occurs over large areas of North America and of more than -30ºC over much of Eurasia. There are also large temperature changes in the tropics and over Southern Hemisphere continents. Large climatic effects would occur in regions far removed from the target areas or the countries involved in the conflict.
Compared to surface temperature decrease, stratospheric temperatures are also severely perturbed as seen in [Fig 5]. The semiannual periodicity at the top is due to enhanced heating during the summers in each hemisphere.
[Fig 5] Change in global average temperature (ºC) profile for the 150 Tg case from the surface to 0.02 mb (80km)
As a resulf of the cooling of the Earth's sruface, evapotranspiration is reduced and the global hydrological cycle is weakened. In addition, Northern Hemisphere summer monsoon circulation collapse, because the driving continent-ocean temperature gradient does not develop. The resulting global precipitation is reduced by about 45%. [Fig 3]
[Fig 6] shows a map of precipitation change for the Northern Hemisphere summer one year after the smoke injection. The largest precipitation [Fig 6] Precipitation changes (mm/day) in response to the 150 Tg [Fig 7] Time series of monthly precipitation from
reductions are in the Intertropical case averaged for June, July, and August of the first year the control, 50 Tg, and 150 Tg cases for the
Convergence Zone and in areas afected following the smoke injection important agricultural region of Iowa
by the North American, Asian, African summer monsoons. The small areas of increased precipitation are in the subtropics in response to a severely weakened Hadley Cell.
[Fig 7] shows that compared to the control, large precipitation reductions in case of 50 Tg and 150 Tg occured. Also it lost its repeated motion and became random. It is clear that these large precipitation reductions would also have agricultural implication.
Results for the 50Tg case
The 50 Tg case produced climate responses very similar to those for the 150 Tg case, but with about half the amplitude. As shown in [Fig. 3], the surface shortwave forcing is about half that of the 150 tg case, and reductions of temperature and precipitation were also about half those of the 150 Tg case. But the time scale of response is about the same.
The forcing and response to an input of 50 Tg are half that of the 150 Tg case even though the aerosol loading is one third, because of a saturation effect. Once almost all the solar radiation is already blocked, additional smoke aerosol particles in the larger case have less of an effect than those put into a clean atmosphere. While the maximum global average precipitation reductions for the 50 Tg case are almost exactly half of those from the 150 Tg case, the 50 Tg temperature changes less than half of those from the 150 Tg case. This difference in the nonlinearity of the response between temperature and precipitation is because the additional cooling in the 150 Tg case does not produce as much change in evapotranspiration, due to the exponential nature of the Clausius-Clapeyron relationship.
While temperature responses in case of 50 Tg are not cold enough to be classified as nuclear "winter", they would still be severe and unprecedented.
The forcing and response to an input of 50 Tg are half that of the 150 Tg case even though the aerosol loading is one third, because of a saturation effect. Once almost all the solar radiation is already blocked, additional smoke aerosol particles in the larger case have less of an effect than those put into a clean atmosphere. While the maximum global average precipitation reductions for the 50 Tg case are almost exactly half of those from the 150 Tg case, the 50 Tg temperature changes less than half of those from the 150 Tg case. This difference in the nonlinearity of the response between temperature and precipitation is because the additional cooling in the 150 Tg case does not produce as much change in evapotranspiration, due to the exponential nature of the Clausius-Clapeyron relationship.
While temperature responses in case of 50 Tg are not cold enough to be classified as nuclear "winter", they would still be severe and unprecedented.
Impacts
The amplitude of the climate changes from the 5 Tg, 50 Tg and 150 Tg cases are compared to those from global warming of the past century in [Fig 8]
In both cases it is clear that all cases would produce unprecedented long-lasting climate change. The 50 Tg and 150 Tg cas
[Fig 9] Last Ice Age [Fig 10] Temperature change of the Earth
The 50 Tg and 150 Tg cases produce cooling as large or larger than that experienced 18000 year ago during the coldest period of the Ice Age. [Fig 10]
MOre recent studies
“Nuclear winter”: A diagnosis of atmospheric general circulation model simulations by Curt Covey Starley L.., Thompson Stephen H. Schneider, 2012
Abstract
We investigate the adiabatic and diabatic thermal balance of an atmospheric general circulation model (GCM) under two conditions: the control case,
representing today's atmosphere, and a “nuclear winter” scenario in which virtually all sunlight in northern hemisphere mid-latitudes is absorbed in the
upper troposphere by prescribed dense smoke clouds hypothesized to result from the burning of many cities in a nuclear war. We also examine the changes in moisture and cloudiness simulated by the model. Our object is to examine the reliability of existing simulations of the climatic response to assumed dense, widespread, high-altitude smoke and to identify improvements needed in model parameterizations. We find that in the smoke-perturbed case our model simulation of land surface temperature is particularly influenced (i.e., warmed) by parameterized diffusion of heat downward from the lower troposphere. In turn the lower troposphere over land is supplied with heat transported from the relatively warm oceans. Thermal balance in the perturbed atmosphere as a whole is dominated by intense solar heating of the upper troposphere smoke layer in mid-latitudes balanced by parameterized dry convection and large-scale dynamical heat transport. Clouds largely disappear in the mid to upper troposphere in smoke-affected regions as a consequence of a decrease in local relative humidity that results from temperature increases and, to a smaller extent, from a reduction of vertical moisture transport. The computation of substantial downward vertical heat diffusion into the lowest model layer is almost certainly an overestimate for the smoke-perturbed conditions of high vertical stability. Consequently, the use of the present diffusive parameterization will, in the absence of other errors, result in an underestimate of the magnitude of land surface cooling in the “nuclear winter” scenario. Current three-dimensional model simulations, however, contain numerous additional omissions and approximations that make it difficult to say whether “nuclear winter” simulations, to date, produce effects that are more or less severe than those that might really occur given the hypothesized smoke amounts and distribution. We believe that the most important areas for GCM enhancement to study climatic effects of nuclear war-generated aerosols include improved surface and planetary boundary layer processes and incorporation of radiatively active aerosol tracer transport and removal.
Abstract
We investigate the adiabatic and diabatic thermal balance of an atmospheric general circulation model (GCM) under two conditions: the control case,
representing today's atmosphere, and a “nuclear winter” scenario in which virtually all sunlight in northern hemisphere mid-latitudes is absorbed in the
upper troposphere by prescribed dense smoke clouds hypothesized to result from the burning of many cities in a nuclear war. We also examine the changes in moisture and cloudiness simulated by the model. Our object is to examine the reliability of existing simulations of the climatic response to assumed dense, widespread, high-altitude smoke and to identify improvements needed in model parameterizations. We find that in the smoke-perturbed case our model simulation of land surface temperature is particularly influenced (i.e., warmed) by parameterized diffusion of heat downward from the lower troposphere. In turn the lower troposphere over land is supplied with heat transported from the relatively warm oceans. Thermal balance in the perturbed atmosphere as a whole is dominated by intense solar heating of the upper troposphere smoke layer in mid-latitudes balanced by parameterized dry convection and large-scale dynamical heat transport. Clouds largely disappear in the mid to upper troposphere in smoke-affected regions as a consequence of a decrease in local relative humidity that results from temperature increases and, to a smaller extent, from a reduction of vertical moisture transport. The computation of substantial downward vertical heat diffusion into the lowest model layer is almost certainly an overestimate for the smoke-perturbed conditions of high vertical stability. Consequently, the use of the present diffusive parameterization will, in the absence of other errors, result in an underestimate of the magnitude of land surface cooling in the “nuclear winter” scenario. Current three-dimensional model simulations, however, contain numerous additional omissions and approximations that make it difficult to say whether “nuclear winter” simulations, to date, produce effects that are more or less severe than those that might really occur given the hypothesized smoke amounts and distribution. We believe that the most important areas for GCM enhancement to study climatic effects of nuclear war-generated aerosols include improved surface and planetary boundary layer processes and incorporation of radiatively active aerosol tracer transport and removal.