Extreme Low Temperature Events Research Articles

Assessment of mortality risks due to a strong cold spell in 2022 in China.

With the intensification of global climate warming, extreme low temperature events such as cold spells have become an increasingly significant threat to public health. Few studies have examined the relationship between cold spells and mortality in multiple Chinese provinces. We employed health impact functions for temperature and mortality to quantify the health risks of the first winter cold spell in China on November 26th, 2022, and analyzed the reasons for the stronger development of the cold spell in terms of the circulation field. This cold spell was a result of the continuous reinforcement of the blocking high-pressure system in the Ural Mountains, leading to the deepening of the cold vortex in front of it. Temperature changes associated with the movement of cold fronts produced additional mortality risks and mortality burdens. In general, the average excess risk (ER) of death during the cold spell in China was 2.75%, with a total cumulative excess of 369,056 deaths. The health risks associated with temperatures were unevenly distributed spatially in China, with the ER values ranging from a minimum of 0.14% to a maximum of 5.72%, and temperature drops disproportionately affect southern regions of China more than northern regions. The cumulative excess deaths exibited the highest in eastern and central China, with 87,655 and 80,230 respectively, and the lowest in northwest China with 27,474 deaths. Among the provinces, excess deaths pronounced the highest in Shandong with 29,492 and the lowest in Tibet with only 196. The study can provide some insight into the mortality burden of cold spells in China, while emphasising the importance of understanding the complex relationship between extreme low temperature events and human health. The outcomes could provide valuable revelations for informing pertinent public health policies.

Investigating the long-term response of plateau vegetation productivity to extreme climate: insights from a case study in Qinghai Province, China.

Over the past three decades, there has been a significant global climate change characterized by an increase in the intensity and frequency of extreme climate events. The vegetation status in Qinghai Province has undergone substantial changes, which are more pronounced than other regions in the Qinghai-Tibet Plateau. However, a clear understanding of the response characteristics of plateau vegetation to extreme climate events is currently lacking. In this study, we investigated the response of net primary productivity (NPP) to different forms of extreme climate events across regions characterized by varying levels of aridity and elevation gradients. Specifically, we observed a significant increase in NPP in relatively arid regions. Our findings indicate that, in relatively arid regions, single episodes of high-intensity precipitation have a pronounced positive effect (higher correlation) on NPP. Furthermore, in high-elevation regions (4000-6000m), both the intensity and frequency of precipitation events are crucial factors for the increase in regional NPP. However, continuous precipitation can have significant negative impacts on certain areas within relatively wet regions. Regarding temperature, a reduction in the number of frost days within a year has been shown to lead to a significant increase in NPP in arid regions. This reduction allows vegetation growth rate to increase in regions where it was limited by low temperatures. Vegetation conditions in drought-poor regions are expected to continue to improve as extreme precipitation intensifies and extreme low-temperature events decrease.

Stratosphere–troposphere synergetic effect on the extreme low-temperature event over China in late November 2022

In late November 2022, most regions in China were hit by a strong northwest-path cold wave, bringing a high-hazard extreme low-temperature event (ELTE). Several parts of Northwest China experienced extremely low temperatures and record-breaking snow depths. A stratosphere–troposphere synergetic effect was suggested to be closely related to the ELTE according to a diagnostic analysis. On the one hand, the concurrent establishment of two blockings in Europe–Northeast Atlantic and North Pacific led to a polar vortex split at the tropopause, and the Arctic Oscillation phase subsequently turned negative. An airflow with high potential vorticity (PV) was squeezed out of the Arctic. Meanwhile, a high-PV air that originated from the lower stratospheric Arctic was conveyed southwards to the western Siberian Plain along the sloping isentropic surface. This condition triggered a tropospheric response in which the East Asia trough deepened due to the intensified cyclonic circulation induced by the high-PV intrusion. On the other hand, downward propagation of stratospheric anomalies accompanied by stratospheric polar vortex displacement and split was observed in mid- and late November, respectively. Changes in stratospheric circulation contributed to enhanced blockings over Europe–Northeast Atlantic in the lower stratosphere or upper troposphere. As a result, the inverted omega-shaped circulation pattern was formed in the middle to upper troposphere, and it consisted of the intensified East Asia trough and two blockings in the upstream and downstream regions. The high-PV air upstream of the East Asia trough was advected to China, which directly led to the outbreak of the ELTE. The establishment of double blockings and the displacement or split of the stratospheric polar vortex can be efficient signals for cold-event prediction in China. This study provides novel insights into the cause of ELTEs under warming climates in the future.

Analysis of the Composite Risk Grade for Multi Extreme Climate Events in China in Recent 60 Years

Much attention has been given to the change rule of a single extreme event, and there are few reports on comprehensive characteristics of multiple extreme events in a certain region. Based on the analyzes of annual frequency of extreme high temperature, extreme low temperature, extreme drought, extreme precipitation, and extreme typhoon events in China from 1961 to 2020, a multi extreme events composite risk grade index (MXCI) was constructed and applied to the comprehensive characteristics analyzes of multiple extreme events in China. The results show that the high value areas of MXCI were mainly located in southeast China and southwest China. Over the past 60 years, the MXCI has shown a decreasing trend in western China and most of southeastern China, and an increasing trend in the middle zone from southwest China to northeast China. Through comparative analysis, MXCI can objectively reflect the comprehensive characteristics of multiple extreme climate events in a region, which is helpful to understand regional extreme climate characteristics and effectively cope with extreme climate risks.

Effects of pre-anthesis low-temperature stress on the mineral components in wheat grains.

The nutritional value of wheat is important to human health. Despite minerals being essential nutrients for the human body, they are often neglected in consideration of the nutritional quality of cereal grains. Extreme low-temperature events have become more frequent due to the current environmental unpredictability, and it is yet unknown how the mineral components in grains are affected by low temperature. To provide valuable information for enhancing the nutritional quality of wheat under potential climatic conditions, we treated different cold-sensitive wheat cultivars at four low-temperature levels during the individual and combined stages of jointing and booting in controlled-environment phytotrons. In general, the contents of P, K, Ca, and Zn in the cold-sensitive cultivar (Yangmai16) and K in the cold-tolerant cultivar (Xumai30) were enhanced by low temperature. However, the accumulation of minerals in mature grains was reduced under low-temperature treatment, except for P, Ca, and Zn in Yangmai16. In addition, the mineral content and accumulation in Yangmai16 (except for Fe) were more susceptible to low temperature during the combined stages, while the mineral content and accumulation of K, Fe, and Zn in Xumai30 were more susceptible to low temperature during the booting stage. Moreover, Yangmai16 under extremely low temperatures (T3 and T4) during booting and Xumai30 under all low-temperature treatments during the combined stages had lower comprehensive evaluation values. These findings offer a crucial reference for enhancing the nutritional quality of wheat grains under climate change.

Extreme low-temperature events can alleviate micronutrient deficiencies while increasing potential health risks from heavy metals in rice

Despite global warming, extreme low-temperature stress (LTS) events pose a significant threat to rice production (especially in East Asia) that can significantly impact micronutrient and heavy metal elements in rice. With two billion people worldwide facing micronutrient deficiencies (MNDs) and widespread heavy metal pollution in rice, understanding these impacts is crucial. We conducted detailed extreme LTS experiments with two rice (Oryza sativa L.) cultivars (Huaidao 5 and Nanjing 46) grown under four temperature levels (from 21/27 °C to 6/12 °C) and three LTS durations (three, six, and nine days). We observed significant interaction effects for LTS at different growth stages, durations and temperature levels on the contents and accumulation of mineral elements. The contents of most mineral elements (such Fe, Zn, As, Cu, and Cd) increased significantly under severe LTS at flowering, but decreased under LTS at the grain-filling stage. The accumulations of all mineral elements decreased at the three growth stages under LTS due to decreased grain weight. The contents and accumulation of mineral elements were more sensitive to LTS at the peak flowering stage than at the other two stages. Furthermore, the contents of most mineral elements in Nanjing 46 show larger variation under LTS compared to Huaidao 5. Accumulated cold degree days (ACDD, °C·d) were found to be suitable for quantifying the effects of LTS on the relative contents and accumulations of mineral elements. LTS at the flowering stage will help alleviate MNDs, but may also increase potential health risks from heavy metals. These results provide valuable insights for evaluating future climate change impacts on rice grain quality and potential health risks from heavy metals.

Assessment of the hazard of extreme low-temperature events over China in 2021

In January 2021, an impressive extreme low-temperature event (ELTE) occurred in China, bringing record-breaking low temperatures to some regions. The comprehensive hazard and the overall situation of ELTEs in the whole of 2021 are still unclear. Accordingly, the overview of ELTEs over the mainland in 2021 and their hazards were systematically reviewed and comprehensively evaluated by using an improved identification and assessment method, which can objectively determine the hazard levels of ELTEs and distinguish spatial differences in the hazard of a single event. A total of 20 ELTEs occurred in 2021; their intensity was remarkably higher than the climatology, while the impacted area and duration were lower than or near the climatology, indicating a normal hazard. In general, the losses of low-temperature related disasters in 2021 were relatively less than the average loss in the past ten years, which is likely related to the low proportion of higher-than-moderately low events in the whole year. ELTEs in 2021 had large impacts on Northwest, North and Northeast China and small impacts on the southeastern Qinghai–Tibet Plateau and western parts of Southwest China. Winter and autumn had a higher-than-normal hazard index for ELTEs due to two high-hazard events in early-to-mid January and early-to-mid November, respectively. These two high-hazard events showed different spatial impacts. The former mainly affected central and eastern parts of China. However, the latter mostly attacked central and western parts of China, especially resulting in high-hazard in parts of Xinjiang.

Negative effects of heat stress on maize yield were compensated by increasing thermal time and declining cold stress in northeast China.

Northeast China (NEC), an important maize region located at high northern latitudes, is undergoing pronounced climate warming. This warming highlights the importance of taking the effects of brief extreme high and low temperature events into account when addressing the impacts of climate warming on crop yields. The spatiotemporal variability of heat and cold stress and their impact on yield were determined by combining climate data, maize phenological observations and yield records from 1981 to 2018 for 17 counties in the major maize cropping area of NEC. Spatially, more severe heat stress during the vegetative phase occurred in the western border and cold stress occurred in the central regions. Both stresses during the reproductive phase and growing degree days (GDD) showed a northeast-southwest gradient. Temporally, we found overall increased (0.5°C•d/yr) heat stress during the vegetative phase, which was predominantly more than five times that during the reproductive phase. The cold stress during the vegetative phase was alleviated by an average of -1.3°C•d/yr, particularly in the central regions. In contrast, exposure to a cold environment during the reproductive phase was intensified, with an average of 0.3°C•d/yr, though a few downward trends mainly occurred near the borders of three provinces. The increasing trend in GDDr was 3.6°C•d/yr, almost twice as high as that in the vegetative phase. The impact of increased heat stress contributed an average yield loss of 0.10 t/ha/10a, while reduced cold stress during the vegetative phase coupled with increased GDD increased yield by 0.42 t/ha/10a. Although cold stress during the reproductive phase had an insignificant impact on yield, its intensity together with the increase in heat stress, especially in the vegetative phase, should be considered when developing appropriate adaptations to increase maize yield in the face of ongoing warming.

Simulation Performance and Case Study of Extreme Events in Northwest China Using the BCC-CSM2 Model

The BCC-CSM2 model is the second generation of the Beijing Climate Center Climate System Model developed by the National Center of China Meteorological Administration. Using the outputs of two versions of the BCC-CSM2 model with different resolutions, namely: BCC-CSM2-MR and BCC-CSM2-HR, their performance in simulating the climate characteristics of Northwest China was compared. The BCC-CSM2-HR had a better ability to simulate the detailed distribution of the average temperature and precipitation in Northwest China, and could delineate the influence of the topography in detail. The extreme events in Northwest China were evaluated further using the BCC-CSM2-HR and the observation data from China Meteorological Data Center. The BCC-CSM2-HR provided a good simulation of the spatial distribution of extreme climate events in Northwest China, and the spatial distribution of TXx, TNx, TXn, and TNn in Northwest China show closer proximity to the observation than that of TX90p, TN90p, TX10p, and TN10p, even in the case of extreme heavy precipitation. This case study of the extreme weather events showed that the BCC-CSM2-HR model had the best simulation performance for extreme high temperature events in Northwest China, followed by extreme low temperature events, and had the worst simulation ability for extreme precipitation events.

Relationships of frequencies of extreme low temperatures with grain yield of some Australian commercial chickpea cultivars

In this study, we examined the relationships between extremes of low temperatures and chickpea yield in 12 field experiments conducted at six sites in the subtropical environment of southeast Queensland (SEQ) from 2014 to 2019. Three commercial chickpea cultivars, PBA-Boundary, PBA-HatTrick and PBA-Seamer, were grown in all the experiments. Cultivars PBA-Pistol, PBA-Monarch and Kyabra were also included in three of these experiments conducted in 2015. In these experiments, the crop experienced a total of 8 to 41 frosts (minimum temperature < = 0 °C), 2 to 41 pre-flowering frosts, 2 to 19 frosts during the critical period, 0 to 13 frosts and 2 to 71 low-temperature days (< = 15 °C) after flowering. The mean yield, which varied from 1 to 3 t/ha, was negatively related to post-flowering frosts (r = − 0.74, p < 0.01) and low-temperature days (r = − 0.76, p < 0.01), and positively related to pre-flowering frosts (r = 0.67, p < 0.05). Each post-flowering frost was associated with a 5% decrease and a low-temperature day with a 1% decrease in yield. The cultivar × site interaction was significant only in the three experiments with six commercial cultivars. This interaction was most likely due to an increase in the sensitivity range with additional cultivars, as indicated by frost damage scores and their relationships with yield. The results imply that extreme low-temperature events after flowering could negatively impact chickpea yield in SEQ and similar subtropical environments. Overcoming these effects through management and breeding should increase and stabilise chickpea yield.

Pteridophyte species richness in the central Himalaya is limited by cold climate extremes at high elevations and rainfall seasonality at low elevations.

There is a consensus that climate factors strongly influence species richness along elevation gradients, but which factors are crucial and how they operate are still elusive. Here, we assess the relative importance of temperature‐related versus precipitation‐related variables and the relative importance of extreme climate versus climate seasonality in driving pteridophyte species richness. We used correlation and regression analyses to relate species richness of pteridophytes, and their two major groups (lycophytes, ferns), in fifty 100‐m vertical bands to climatic factors representing different aspects of climatic conditions (general climate, stressful climate, and climate seasonality). Variation partitioning analysis was used to determine the relative importance of each group of climatic factors on species richness. Across the entire elevational gradient, species richness had a parabolic response to mean annual temperature (adjusted R 2 = .87−.91), and a linear response to annual precipitation (adjusted R 2 = .82). Mean annual temperature and annual precipitation in the second‐order polynomial model together explained 96.3%−98.7% of the variation in species richness. The variation in species richness uniquely explained by minimum temperature of the coldest month was much greater than that uniquely explained by temperature seasonality, but the variation in species richness uniquely explained by precipitation during the driest month was much smaller than that uniquely explained by precipitation seasonality. Overall, extreme climate variables explained slightly more variation than did climate seasonality. Our study suggests that pteridophyte richness along the elevational gradient is largely driven by a combination of both temperature‐ and precipitation‐related parameters, although precipitation‐related variables play a slightly stronger role, and that extreme low temperature events (at high elevations) and seasonal precipitation variability (at low elevations) are the strongest determinants of pteridophyte species richness.

Impacts of Extreme Climate Events on Future Rice Yields in Global Major Rice-Producing Regions.

Under the dual impacts of climate change and COVID-19, there are great risks to the world’s food security. Rice is one of the three major food crops of the world. Assessing the impact of climate change on future rice production is very important for ensuring global food security. This article divides the world’s main rice-producing regions into four regions and uses a multivariate nonlinear model based on historical economic and climatic data to explore the impacts of historical extreme climatic events and economic factors on rice yield. Based on these historical models, future climatic data, and economic data under different shared socioeconomic pathways (SSPs), the yields of four major rice-producing regions of the world under different climate change scenarios (SSP126, SSP245, and SSP585) are predicted. The research results reveal that under different climate change scenarios, extreme high-temperature events (Tx90p) and extreme precipitation events (Rx5day, R99pTOT) in the four major rice-producing regions have an upward trend in the future. Extreme low-temperature events (Tn10p) have a downward trend. In the rice-producing regions of Southeast Asia and South America, extreme precipitation events will increase significantly in the future. The prediction results of this model indicate that the rice output of these four major rice-producing regions will show an upward trend in the future. Although extreme precipitation events will have a negative impact on rice production, future increases in rice planting areas, economic development, and population growth will all contribute to an increase in rice production. The increase in food demand caused by population growth also brings uncertainty to global food security. This research is helpful for further understanding climate change trends and risks to global rice-production areas in the future and provides an important reference for global rice-production planning and risk management.

Effects of Low-Temperature Stress during the Anther Differentiation Period on Winter Wheat Photosynthetic Performance and Spike-Setting Characteristics.

Climate change has caused frequent extreme low-temperature events to threaten global food security. Spring low-temperature stress is one of the major limiting factors for high and stable yields of wheat. We used two wheat varieties differing in spring cold-sensitivity (cold-tolerant variety Yannong 19 and cold-sensitive variety Xinmai 26) to examine the effects of low-temperature stress during the anther differentiation period on wheat photosynthetic performance and spike-setting characteristics. Low-temperature stress was simulated in a climate box at −2 °C, 0 °C or 2 °C (night) and 15 °C (day) for 24 h, 48 h or 72 h. With the extension of the treatment time and the decrease of temperature, the photosynthetic rate, stomatal conductance and transpiration rate of wheat leaves gradually decreased. All treatments except −2 °C for 72 h recovered slowly within 7–15 days after treatment. Low-temperature stress greatly reduced grains per spikelet, 1000-grain weight and yield per plant. By analyzing the spikelets in different stalk locations (upper, middle and lower), we found that the number of upper spikelets was significantly less than lower and middle spikelets after low-temperature stress. The sterile grain of upper spikelets (Xinmai 26, for example) can reach 100% at −2 °C for 48 h and 72 h, and the yield loss rate was 90.52% at 2 °C for 24 h, which was much higher than for the lower spikelets (60.73%) and middle spikelets (50.94%). Overall, these findings suggest that low-temperature stress during the anther differentiation period alters the photosynthetic activity involved in the accumulation of dry matter in wheat, which leads to delaying young spike growth, especially for upper spikelets, and ultimately in a decrease in yield.

Arctic air mass triggered the extreme temperature events recorded in the Laohugou ice core from the northeastern Tibetan Plateau

The frequency and the intensity of extreme temperature events have both increased globally because of the effects of climate warming. Such extreme events should be distinct in high-elevation areas owing to the phenomenon of elevation-dependent warming; however, corroborating evidence remains limited because of scarce observations. This study used the percentile method to identify annual extreme temperature events recorded in the δ18O of the Laohugou ice core (1960–2006) retrieved from the high-elevation area of the northeastern Tibetan Plateau (NETP). Comparison of these events with synchronous observations obtained at surrounding meteorological stations indicated that extreme temperature events identified from the ice core corresponded well with most temperature observations from the meteorological stations, suggesting that the δ18O record could be considered a reasonable proxy for regional temperature. However, occasional discord between the ice core and station records might reflect specific climatic shifts. Using circulation synthesis, the influencing circulation mechanism of each event was determined on the basis of differences in atmospheric parameters between each event and the average climatic state during 1970–2000. A double blocking high with warming over the Ural Mountains and east of Kuril–Kamchatka resulted in Eurasian warming, which transported warm air to the NETP and triggered the extreme high-temperature events. Conversely, a polar vortex in the Arctic led to a cold low over Eurasia, which transported cold air to the NETP causing extreme low-temperature events. The finding that variation of the Arctic air mass triggers extreme temperature events at high elevations in the NETP provides crucial insight for improved comprehension and forecasting of regional extreme temperature events.

Characteristics of the Winter Extreme Low Temperature Events in Ningxia and their Relationship with the Arctic Sea Ice Coverage Anomalies in Autumn

Characteristics of the Winter Extreme Low Temperature Events in Ningxia and their Relationship with the Arctic Sea Ice Coverage Anomalies in Autumn

Cold Stress in Wheat: Plant Acclimation Responses and Management Strategies.

Unpredicted variability in temperature is associated with frequent extreme low-temperature events. Wheat is a leading crop in fulfilling global food requirements. Climate-driven temperature extremes influence the vegetative and reproductive growth of wheat, followed by a decrease in yield. This review describes how low temperature induces a series of modifications in the morphophysiological, biochemical, and molecular makeup of wheat and how it is perceived. To cope with these modifications, crop plants turn on their cold-tolerance mechanisms, characterized by accumulating soluble carbohydrates, signaling molecules, and cold tolerance gene expressions. The review also discusses the integrated management approaches to enhance the performance of wheat plants against cold stress. In this review, we propose strategies for improving the adaptive capacity of wheat besides alleviating risks of cold anticipated with climate change.

Identification of winter long-lasting regional extreme low-temperature events in Eurasia and their variation during 1948–2017

Compared with short-duration events, long-lasting regional extreme low-temperature events (RELTEs) often have more severe impacts on human societies due to the induced persistence and large geographic area of related weather and climate disaster. Accordingly, an improved objective technique was applied to identify all long-lasting RELTEs in Eurasia from the winter of 1948/1949 to 2017/2018, followed by an in-depth discussion of its variation in terms of the annual frequency, duration, impacted area, mean intensity, maximum intensity, and a comprehensive index. The RELTE lasting for 52 d in the winter of 2007/2008 exhibited the longest duration, largest impacted area, and a greatest comprehensive index, which induced extremely low temperatures for more than 20 d in Western Asia, Central Asia, and China. During the past 70 winters, the frequency of long-lasting RELTEs decreased, especially after the late 1960s. Nevertheless, the mean and maximum intensities and comprehensive index exhibited distinctly increasing trends. All indicators of winter long-lasting RELTEs had a similar inter-decadal fluctuation featured by two noticeable peaks occurring around 1970 and 2007, and a remarkable recovery was discovered in the period of late 1990s to mid-2010s, especially for the occurrence of super long-lasting events. Significantly, winter long-lasting RELTEs in Eurasia showed distinct trends under various decadal climate backgrounds, i.e., a strong negative or weak positive trend in the accelerated warming period and conversely, a strong positive or weak negative trend in the warming slowdown stage. These findings indicate that we should be alert of the similar future recovery of winter long-lasting RELTEs in Eurasia, which are likely to occur in the slowdown period of global warming.

The study of changing characteristics of the winter temperature and extreme cold events in China over the past six decades

AbstractBy using winter (December–February) daily temperature at 1629 meteorological stations over China during 1960/61‐2017/18, spatial–temporal changes and probability distribution characteristics of winter temperature and extreme cold events in China were analysed, with a special emphasis on the warming hiatus in China. The results are as follows: (1) the winter temperature in China showed an overall upward trend during the past six decades. However, since the winter of 2006 (so‐called the warming hiatus period), the winter temperature in China has remained stable and even decreased slightly. (2) There is an obvious difference in winter temperature between South China and North China. North China witnessed a more obvious temperature rise during the warm period (1986–2005) than South China did. However, since 2006, winter temperature in most parts of North China has dropped slightly, with a marked increase in extreme cold events. In contrast, South China did not undergo an obvious temperature drop during the hiatus period. (3) The range of temperature change in North China is larger than that in South China. The range of minimum temperature is also wider than that of maximum temperature, with a noticeable increase in extreme low temperature events since 2006. In such situation, North China is more likely to encounter extreme low temperature events, such as cold wave and low temperature weather. (4) China has experienced an increase in extreme cold events during the hiatus period. There is an obvious upward trend in regional long‐lasting extreme cold events (3–5 and 11–20 days duration). Consequently, this study has revealed that winter temperature and frequency of extreme cold events in China was not only influenced by global warming, with a persistent warming, but also showed an obvious inter‐decadal variation which is associated with the natural forcing. It indicates that the natural forcing factor is also a main factor influencing and modulating the winter temperature change at the inter‐decadal scale at the regional scale as China even in the era of the global warming caused by anthropogenic forcing.

Climatic Events and Natural Disasters of 21st Century: A Perspective of Pakistan

In recent years, the frequent occurrence of natural calamities in the world has gained much attention due to infrastructure and life losses. Increase in global temperature has threatened the earth’s climate, causing unpredictable and extreme weather events more often. These events were both short-term as well as long-term. In spite of insufficient monitoring coverage of inner areas and high altitudes, an intensification of average yearly temperature has been observed after the 20th century in many regions of Asia. Pakistan has faced a number of natural disasters including severe floods, devastating earthquakes, disturbing droughts, distressing smog, extreme temperature and torrential rainfall patterns. These calamities have affected people economically, socially, physically and mentally by posing a threat to earth, its species and their livelihood. This paper was aimed to document the natural calamities in Pakistan since the beginning of 21st century till date. The country is facing the problem of intense and longer summers and has witnessed two intense heat waves. Moreover, in some areas, extensive droughts are threatening crops, freshwater supply and wildlife. In recent years, the problem of smog has emerged in Pakistan, especially in Punjab. The problem is getting worse in every coming year due to overpopulation, cities expansion, increased emission of greenhouse gases, open burning of crop residues and extreme reliance on fossil fuels for energy purpose. So far in this century, Pakistan has faced 3 droughts, 2 heat waves, 10 severe floods, 27 major earthquakes, 2 consecutive sessions of severe smog and extreme high and low temperature events. Some of the deadliest events were; 2005 Kashmir earthquake claiming 87,350 human lives and 2010 flood impacting nearly 20 million people with 1,781 causalities. Change in climate is posing a severe threat to species, livelihood of the human beings and the earth. Global warming is causing warming of oceans and consequently rise in sea level. Climate change affects average as well as extreme temperatures hence increasing the probability climate-related disasters. Thus, global warming is causing a chain of catastrophic events that make the problem even more complex to understand.

Evaluation and ensemble projection of extreme high and low temperature events in China from four dynamical downscaling simulations

AbstractExtreme climate events are often of great interest because of their close relationship with meteorological and hydrological disasters. In this study, four RCM simulations driven by different GCMs (CSIRO‐Mk3.6.0, EC‐EARTH, HadGEM2‐ES, and MPI‐ESM‐MR) are used as an ensemble to project changes in extreme high and low temperatures in China as represented by selected Expert Team on Climate Change Detection indices. Each simulation is performed at 25 km resolution from 1980 to 2099 using RegCM4.4 RCM. Results show the following: (a) All four reasonably reproduce climatological maximum daily maximum temperature (TX), warm spell duration, minimum daily minimum temperature (TN), and cold spell duration, but the majority shows relatively weak ability to capture climatological warm day and cold night frequencies. (b) Although the RCM homogenizes much of the variance originally shown between driving GCM simulations, marked dissimilarities are still shown in western China across the four downscaling simulations, implying a dependency on the individual GCM‐driven RCM simulation for this region. (c) All of China shows an increase in maximum TX, warm days, warm spell duration, minimum TN, and a decrease in cold nights and cold spell duration, during the near‐term, middle‐term, and long‐term. The Tibetan Plateau and its adjacent regions show more significant changes in extreme temperature, indicating stronger sensitivity to changes in extremes. RCM downscaling projects less significant change in extreme temperatures than the driving GCM. (d) The ensemble of RCM simulations projects that area‐averaged maximum TX, warm days, warm spell duration, and minimum TN increase over China as a whole by 2.5°C, 21.1%, 43.6 days, and 3.3°C, respectively, while cold nights and cold spell duration decrease by 6.8% and 2.0 days, respectively during the long‐term under the RCP4.5 scenario relative to 1986–2005. Future episodes of extreme high temperature are likely to require more research as they become more common.