Frost depth increase under a nuclear winter scenario projected to sever piped-water access in the Northern Hemisphere

Non-climatic factors and long-term, continental-scale changes in seasonally frozen ground

The maximum annual freeze depth (MFD) is a primary indicator of the thermal state of frozen ground, affecting ecosystems, hydrological processes, vegetation growth, infrastructure, and human activities in cold regions. It is thus important to quantify the past, present, and future spatial and temporal variability of MFD at the hemispheric scale. We develop a data‐driven MFD simulation method within a machine learning framework, integrating MFD observations from meteorological stations and several environmental predictors, to analyze past and future scenarios in the Northern Hemisphere (NH). Based on ERA5 reanalysis estimates and historical to future CMIP6 scenarios, the NH MFD averaged 133 cm (ERA5) and 131 cm (CMIP6) during 1981–2010, and will vary 81–112 cm during 2015–2100 depending on the emission scenario. During 1950–2013, MFD decreased by 0.37 cm/a (ERA5) versus 0.22 cm/a (CMIP6), and is projected to decrease 0.16–0.69 cm/a by 2100. During 1981–2010, MFD decreased by an average of 19.1% (ERA5) and 13.9% (CMIP6), with a net change of −17 cm (ERA5) and −13 cm (CMIP6). Depending on the emission scenario, MFD will decrease 11% (−12 cm) to 42% (−19 cm) between 2015 and 2099 relative to the 1981–2010. Warming, increased moisture, warmer cold seasons, warmer warm seasons, shallower snow depths, and increased vegetation cover all lead to a reduction in MFD. The results from this novel machine learning approach provide useful insights regarding the fate of future frozen ground changes.

We reeaxmine the “nuclear winter” hypothesis with a three‐dimensional global model modified to allow for localized injection of smoke, its transport by the simulated winds, its absorption of sunlight, and its removal by model‐simulated precipitation. Smoke injected into the troposphere is driven upward by solar heating. The tropopause, initially above the smoke, reforms below the heated smoke layer and separates it from precipitation below. Although much smoke is scavenged while the thermal structure is being altered, the residence time of the remaining smoke is greatly increased. We find, particularly for July conditions, a longer‐lasting “nuclear winter” effect than was found in earlier modeling studies in which normal tropospheric residence times were assumed. In January the smaller solar flux in the northern hemisphere allows faster removal of smoke than in July. Significant cooling of the northern hemisphere continents is predicted; its dependence on season and injected smoke mass is described.

In the last quarter of the twentieth century total war means nuclear war. This is a difficult subject to address. The literature devoted to it is naturally copious. Every aspect of the problem has been tackled and from most points of view. Henry Kissinger's impressive record as a major actor in international politics adds to the significance of the book that launched his career in 1957: Nuclear Weapons and Foreign Policy. He has had few rivals, but many successors and imitators. Scientists have always had much to contribute to the debate. In 1950 Einstein warned his American television audience of the risk of 'general annihilation'. In 1983 a conference of scientists at Cambridge, Massachusets was told that war might well be followed by an almost equally catastrophic 'nuclear winter'. Crudely summarised, the theory was that enough nuclear explosions would produce smoke and dust in sufficient quantities to obscure the light of the sun, sharply lower the temperature and, when combined with other effects, jeopardise the survival of the species in at least the northern hemisphere.2KeywordsNuclear WeaponBallistic MissileAmerican WriterCentral FrontNuclear WarheadThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Remote sensing spatiotemporal patterns of frozen soil and the environmental controls over the Tibetan Plateau during 2002–2016

Recent studies predict that even a medium‐scale nuclear war in the northern hemisphere may eause cooling in the mid‐latitudes of the southern hemisphere. The impact of such cooling on agriculture depends on the magnitude, duration and starting date of the southern nuclear winter. Cooling in the middle of the growing season (summer) ean have serious consequences, whereas cooling during the dormant season (winter) may have little effect. Various temperature reduction schemes are considered. A cooling of 5°C, equivalent to temperatures during the Last Glacial maximum, dramatically reduces primary production. A spring cooling of 3°C and other seasons of 1°C eliminates yields from many warm temperate crops and lowers grass production. Smaller temperature decreases have less effect. Given the limitations and uncertainties of the models, these scenarios should be treated with caution; but our results show that a northern hemisphere war could significantly affect New Zealand agriculture.

Introduction Rising global temperatures lead to milder winters with higher minimum temperatures and shorter periods of sub-zero conditions, but more frequent freezing and thawing in many boreal regions. Additionally, snow cover duration has decreased in recent decades in the northern hemisphere, and the overall amount of seasonal snow has declined (Pulliainen et al. 2020). This impacts the relationship between soil and air temperatures since snow acts as an insulator, helping to prevent deep soil freezing. Soil temperature and frost depth are crucial for the functioning of high-latitude ecosystems, as they influence tree water uptake, photosynthesis, and growth (e.g. Jyske et al. (2011), Lintunen et al. (2020)). For dwarf shrubs on the forest floor, snow’s insulating effect is even more critical in cold climates (Campbell et al. 2005). Soil temperature experiments are usually carried out in controlled environments such as laboratories or greenhouses, often focusing on shrubs or tree seedlings. However, some previous field studies have been conducted in mature boreal forests (e.g. Bergh and Linder (2001), Jyske et al. (2011)). In this study, we blocked snow from reaching the forest floor for two consecutive winters in a mature boreal forest to examine its effects on soil temperature, forest floor respiration, tree hydraulics, stem and root growth, as well as the growth of dwarf shrubs. Methods The experiment was conducted at SMEAR II station (Hari and Kulmala 2005) in southern Finland. The core of the SMEAR II stand with long-term tree-measurements was our control site and the snow removal treatment was done in its close proximity by preventing snow from falling to the ground with four shelters with total area of 360 m2. Each shelter was constructed around 2-3 study trees so that the tree canopies reached above the shelters. The shelters were removed for the snowless periods. The studied species were Scots pine, Norway spruce, silver birch, and a dwarf shrub bilberry. We measured air temperature, snow depth, soil temperature, soil moisture and root temperature at the control and treatment sites. Forest floor respiration was measured monthly with a dark manual chamber. Tree sap flow was measured with constant heat-dissipation probes and sap pressure from birches with pressure transducers. We measured stem diameter growth from tree cores and pine fine root growth with root ingrowth bags. We also measured coarse root hydraulic conductivity, bark osmolality and frost damages. Regarding dwarf shrubs, we measured diameter growth of the stem, elongation growth, fine root growth, leaf mass, leaf area, and the percentage of dead ramets. Results and discussion The absence of snow cover led to lower soil temperatures, which in turn reduced forest floor respiration during winter and spring. At the same time, the sensitivity of respiration to temperature appeared to increase, possibly due to the exposure of forest floor vegetation to cold air. The lack of snow also caused bilberry mortality, but the surviving plants grew taller and developed larger leaves, likely as a compensatory response to biomass loss. Tree hydraulics were also affected, with reduced water uptake in spring and a delayed start of the sap pressure season in birch. Pine and birch showed a tendency for reduced growth under snow exclusion, whereas spruce exhibited increased growth. However, previous studies have shown that the growth responses may have a time lag (Repo et al. 2021). Coarse root traits, such as water content and cellular frost damage, remained unaffected by the treatment. This study adds to our understanding of how changing snow cover influences springtime tree and forest floor processes in mature boreal forests. However, it also highlights the need for further research on mature trees to fully grasp the long-term impacts.

Permafrost and seasonally frozen ground regions occupy approximately 24% and 55%, respectively, of the exposed land surface in the Northern Hemisphere. The areal extent, timing, duration, and depth of the near-surface soil freeze and thaw have a significant impact on plant growth, energy, and water and trace gas exchanges between the atmosphere and the soils in cold seasons/cold regions. Satellite remote sensing combined with ground “truth” measurements have been used to investigate seasonally frozen ground and permafrost at local to regional scales with some success. The objective of this paper is to provide an overview of satellite remote sensing techniques applied to study seasonally frozen ground and permafrost over the last few decades. Remote sensing of permafrost terrain and surface freeze/thaw cycles typically uses a combination of imaging in optical and thermal wavelengths, passive microwave sensing, and active microwave remote sensing using scatterometer and Synthetic Aperture Radar (SAR). No single sensor is capable of providing the range of observations needed. SAR imaging provides information on the timing, duration, and regional progression of the near-surface soil freeze/thaw status in cold seasons/regions with a relatively high spatial resolution, but repeat times of existing satellites are relatively long compared to the rate of change of the soil freeze/thaw cycle in fall and spring. Spaceborne passive microwave sensors offer more frequent coverage at several wavelengths, but with substantially lower spatial resolution. Optical and thermal sensors provide a middle ground in spatial resolution and temporal sampling between SAR and passive microwave satellites, but a known relationship between permafrost (and freeze/thaw depth) and corresponding environmental factors needs to be provided. Overall, microwave remote sensing is a promising technique for detecting near-surface soil freeze/thaw cycles over snow-free land. The potential for using land surface temperature derived from satellite visible and near-infrared sensors to study soil freezing and thawing processes is substantial. Satellite remote sensing data products—such as for snow cover extent, snow depth, snowmelt, land surface type, Normalized Difference Vegetation Index (NDVI), surface albedo, surface wetness, and soil moisture—can be very helpful for frozen ground studies at local, regional, and global scales.

Characteristics of the geomagnetic field are shown by plotting equivalent current functions J on successively deeper spherical surfaces within the earth. As the depth increases, the amplification of the higher-order spherical harmonic terms increases, so that, in effect, higher-order terms successively are brought into focus. Maps of J reveal that negative extrema of J are much more prominent than positive extrema and are equally so in the northern and southern hemispheres. Coriolis forces are surely important in the generation of the earth's magnetic field. Since the Coriolis forces are of opposite sign in the northern and southern hemispheres, we have to seek a second factor that changes sign between the two hemispheres. It is suggested that this factor implies a general circulation pattern in the core that is antisymmetric between the two hemispheres.

Abstract. The electron density data recorded by the Langmuir Probe Instrument (ISL, Instrument Sonde de Langmuir) onboard the DEMETER satellite have been collected for nearly 4 yr (during 2006–2009) to perform a statistical analysis. During this time, more than 7000 earthquakes with a magnitude larger than or equal to 5.0 occurred all over the world. For the statistical studies, all these events have been divided into various categories on the basis of the seismic information, including Southern or Northern Hemisphere earthquakes, inland or sea earthquakes, earthquakes at different magnitude levels, earthquakes at different depth levels, isolated events and all events. To distinguish the pre-earthquake anomalies from the possible ionospheric anomalies related to the geomagnetic activity, the data were filtered with the Kp index. The statistical results obviously show that the electron density increases close to the epicentres both in the Northern and the Southern Hemisphere, but the position of the anomaly is slightly shifted to the north in the Northern Hemisphere and to the south in the Southern Hemisphere. The electron density related to both inland and sea earthquakes presents an anomaly approximately close to the epicentres, but the anomaly for sea earthquakes is more significant than for inland earthquakes. The intensity of the anomalies is enhanced when the magnitude increases and is reduced when the depth increases. A similar anomaly can also be seen in the statistical results concerning the isolated earthquakes. All these statistical results can help to better understand the preparation process of the earthquakes and their influence up to the ionospheric levels.

Sensitivity of boundary layer features to depth-dependent baroclinic pressure gradient and turbulent mixing in an ocean of finite depth

This chapter looks at the nuclear winter project, an outcome of global modeling. The idea that the Earth could be plunged into a “nuclear winter” as the catastrophic outcome of a nuclear war was announced by a group of leading climate and environment scientists from the United States, Western Europe, and the Soviet Union shortly after Ronald Reagan delivered his “Star Wars” speech in March 1983. Drawing on experiments with data-based computer models, these scholars claimed that a nuclear war, unlike the two world wars, would be not simply a regional, but a truly global disaster. Nuclear missiles, detonated over urban areas, would ignite massive fire storms, which in turn would propel soot particles and aerosols into high levels of the atmosphere. As a result, the computer models predicted, a dust shield would emerge that would be transported by air currents to both the Northern and Southern hemispheres.

Whale mining, whale saving

Current snow state descriptions and estimates of major snow characteristics (snow coverduration, maximum winter snow depth, snow water equivalent) up to 2010 have beenrecorded from 958 meteorological stations in Russia. Apart from the description oflong-term averages of snow characteristics, the estimates of their change thatare averaged over quasi-homogeneous climatic regions are derived and regionaldifferences in the change of snow characteristics are studied. In recent decades, theRussian territory has experienced an increase in snow depth, both winter averageand maximum snow depths, against the background of global temperature riseand sea ice reduction in the northern hemisphere. The first generalized regionalcharacteristics of maximum snow water equivalent in the winter season have beenobtained. According to field observations, an increase in water supply has beenrevealed in the north of the East European Plain, in the western part by 4.5%(10 yr) − 1 and in the eastern part by6% (10 yr) − 1. This characteristicalso increases by ∼ 6% (10 yr) − 1 in the southern forest zone of Western Siberia and in the Far East.Snow water equivalent in central Eastern Siberia increases by 3.4%(10 yr) − 1. From snow course observations in the forest, a tendency for a decrease in water supply (−6.4% (10 yr) − 1 is only found in the southwest of the East European Plain. Snow cover characteristics,being a product of several climate-forming factors that simultaneously affected them,change nonlinearly and different characteristics may and often do change differently withtime. Therefore, one cannot assume that having information about the trend ofone of the snow characteristics implies knowledge of the trend sign of others. Inparticular, whilst during the past four decades over the Russian Federation most snowcover characteristics—including the most important of them responsible for watersupply—have increased, the only quantity that is reliably monitored from space(snow cover extent) has decreased, but in the last two decades this decrease hasceased. These tendencies are opposite to those observed in Canada and Alaska.

The decadal change in the spring snow depth over the Tibetan Plateau and impact on the East Asian summer monsoon are investigated using station observations of snow depth data and the NCEP–NCAR reanalysis for 1962–93. During spring (March–April), both the domain-averaged snow depth index (SDI) and the first principal component of the empirical orthogonal function (EOF) analysis exhibit a sharp increase in snow depth after the late 1970s, which is accompanied by excessive precipitation and land surface cooling. The correlation between SDI and precipitation shows a coherent remote teleconnection from the Tibetan Plateau–northern India to western Asia. It is found that the increased snow depth over the plateau after the mid-1970s is concurrent with a deeper India–Burma trough, an intensified subtropical westerly jet as well as enhanced ascending motion over the Tibetan Plateau. Additional factors for the excessive snowfall include more moisture supply associated with the intensification of the southerly flow over the Bay of Bengal and an increase of humidity over the Indian Ocean. While the extensive changes of the circulation in Eurasia and the Indian Ocean are associated with a climate shift in the Northern Hemisphere after the mid-1970s, some regional factors such as the enhanced coupling between the sea surface temperature (SST) warming in the northern Indian Ocean/Maritime Continent and the tropical convective maximum (TCM), as well as local feedback of the land surface cooling due to excessive snow cover and the atmosphere may contribute to the regional circulation changes. The former enhances the western Pacific subtropical in the South China Sea–Philippine Sea through modulation of the local Hadley circulation and results in stronger pressure gradients and fronts in southeastern and eastern Asia. A close relationship exists between the interdecadal increase of snow depth over the Tibetan Plateau during March–April and a wetter summer rainfall over the Yangtze River valley and a dryer one in the southeast coast of China and the Indochina peninsula. It is proposed that the excessive snowmelt results in a surface cooling over the plateau and neighboring regions and high pressure anomalies that cause a more northwestward extension of the western Pacific subtropical high in the subsequent summer. Additionally, the increased surface moisture supply provides more energy for the development of the eastward-migrating low-level vortex over the eastern flank of the Tibetan Plateau. Both factors lead to a wetter summer in the vicinity of the Yangtze River valley.