As a widely used reconstruction algorithm in quantum state tomography, maximum likelihood estimation tends to assign a rank-deficient matrix, which decreases estimation accuracy for certain quantum states. Fortunately...As a widely used reconstruction algorithm in quantum state tomography, maximum likelihood estimation tends to assign a rank-deficient matrix, which decreases estimation accuracy for certain quantum states. Fortunately, hedged maximum likelihood estimation （HMLE） [Phys. Rev. Lett. 105 （2010）200504] was proposed to avoid this problem. Here we study more details about this proposal in the two-qubit case and further improve its performance. We ameliorate the HMLE method by updating the hedging function based on the purity of the estimated state. Both performances of HMLE and ameliorated HMLE are demonstrated by numerical simulation and experimental implementation on the Werner states of polarization-entangled photons.展开更多
This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us...This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us to investigate the connectedness at conditional quantiles.Our sample includes four major DeFi’s and six ASEAN stock markets,spanning from March 2018 to December 2022.The static results indicate a moderate level of return transmission between the system at mean and median quantile.This propagation increases substantially under extreme market conditions,establishing an asymmetric transmission across quantiles.Despite being a relatively new asset class,DeFi dominates the equity market and acts as the primary shock transmitter to the system in most instances.The dynamic analysis reveals that total system connectedness fluctuates over time and quantiles.The total system connectedness peaked during the COVID-19 and the Russia–Ukraine conflict period,indicating the impact of global events on system transmission.The optimal weight and hedge ratio estimated using the DCC-GARCH model indicate that DeFi is beneficial for portfolio construction and risk management.The rising trend in dynamic optimal weight and hedge ratio during the COVID-19 pandemic demonstrates that investors should decrease their investments in DeFi and increase hedging costs.Therefore,portfolio managers and investors should readjust their portfolio allocation in a timely manner according to different market states to build additional effective hedging and diversification strategies to avoid large losses and to reduce portfolio risk exposure.展开更多
Effective management of water resources,especially groundwater,is crucial and requires a precise understanding of aquifer characteristics,imposed stresses,and the groundwater balance.Simulation-optimization models pla...Effective management of water resources,especially groundwater,is crucial and requires a precise understanding of aquifer characteristics,imposed stresses,and the groundwater balance.Simulation-optimization models plays a vital role in guiding planners toword sustainable long-term aquifer exploita-tion.This study simulated monthly water table variations in the Kashan Plain over a ten-year period from 2008 to 2019 across 125 stress periods using the GMS model.The model was calibrated for both steady-state and transient conditions for the 2008–2016 period and validated for the 2016–2019 period.Results indicated a 4.4 m decline in groundwater levels over the 10-year study period.Given the plain's location in a arid climatic zone with limited effective precipitation for aquifer recharge,the study focused on ground-water extraction management.A modified two-point hedging policy was employed as a solution to mitigate critical groundwater depletion,reducing the annual drawdown rate from 0.44 m to 0.31 m and conserving 255 million cubic meters(mcm)of water annually.Although this approach slightly decreased reliability(i.e.the number of months meeting full water demands),it effectively minimized the risk of severe droughts and irreparable damages.This policy offers managers a dynamical and intelligent tool for regulating groundwater extraction,balancing aquifer sustainability with agricultural and urban water requirements.展开更多
In this study,we propose a Gram-Charlier expansion approach to investigate the impact of skewness and kurtosis on production and hedging decisions.Consistent with the existing literature,we find that skewness and kurt...In this study,we propose a Gram-Charlier expansion approach to investigate the impact of skewness and kurtosis on production and hedging decisions.Consistent with the existing literature,we find that skewness and kurtosis do not affect decisions regarding optimal production;however,they significantly influence optimal hedging decisions.We observe that positive skewness with platykurtic spot prices or negative skewness with leptokurtic spot prices often leads to over-hedging when the initial forward contract price exceeds its expected value.Conversely,under-hedging is expected when the initial forward contract price falls below its expected value.In other conditions,skewness can either promote or impede speculative future trading.Using the Gram-Charlier expansion of the spot price density function,we find that optimal future positions depend on forward prices,the hedgers’risk preference,and the spot price distribution.Simulations validate our findings on the impact of skewness and kurtosis on future hedging.Finally,we analyze of a cotton storage and forward contracting dataset to illustrate the application of our methodology and support our theoretical results.展开更多
This paper employs the PPO(Proximal Policy Optimization) algorithm to study the risk hedging problem of the Shanghai Stock Exchange(SSE) 50ETF options. First, the action and state spaces were designed based on the cha...This paper employs the PPO(Proximal Policy Optimization) algorithm to study the risk hedging problem of the Shanghai Stock Exchange(SSE) 50ETF options. First, the action and state spaces were designed based on the characteristics of the hedging task, and a reward function was developed according to the cost function of the options. Second, combining the concept of curriculum learning, the agent was guided to adopt a simulated-to-real learning approach for dynamic hedging tasks, reducing the learning difficulty and addressing the issue of insufficient option data. A dynamic hedging strategy for 50ETF options was constructed. Finally, numerical experiments demonstrate the superiority of the designed algorithm over traditional hedging strategies in terms of hedging effectiveness.展开更多
This paper examines the dependence,systemic risk spillover,return and volatility spillover,and portfolio implications across various timescales between the Green Bond(GB)and U.S.S&P 500 Stock(SP),Vanguard Total Wo...This paper examines the dependence,systemic risk spillover,return and volatility spillover,and portfolio implications across various timescales between the Green Bond(GB)and U.S.S&P 500 Stock(SP),Vanguard Total World Stock Index Fund(VT),Bitcoin(BTC),Ethereum(ETH),Ripple,OIL,and GOLD markets.The sample period is August 07,2015–October 6,2023,covering periods of instability during the COVID-19 pandemic and the Russia–Ukraine conflict.Using the wavelet–copula–conditional value-atrisk and wavelet-multivariate asymmetric-GARCH framework,our main results show that the systemic risk and return,volatility spillovers,and diversification opportunities are portfolio-specific and timescale-dependent.Specifically,there is a negative long-term correlation for the pairs GB-SP and GB-OIL,whereas the pair GB–GOLD pair is positively correlated in the short term.GB can mitigate the risk of other markets.In terms of the portfolio implications,GB weakly hedges BTC and ETH during normal and turbulent periods but has a strong ability to hedge VT in the short term and SP in the mid and long term.Regarding hedging effectiveness,the role of GB for GOLD and VT is noted.展开更多
A semantics-based model is proposed to enable weakened hedges, such as ＂more or less＂ and ＂roughly＂ in the context of linguistic multi-criteria decision making. First, the resemblance relations are defined based o...A semantics-based model is proposed to enable weakened hedges, such as ＂more or less＂ and ＂roughly＂ in the context of linguistic multi-criteria decision making. First, the resemblance relations are defined based on the semantics of terms on the domain. Then, the hedges can be represented after the upper and loose upper approximations of a linguistic term are derived. Accordingly, some compact formulae can be derived for the semantics of linguistic expressions with hedges. Parameters in these formulae are objectively determined according to the semantics of original terms. The proposed model presents a more natural way to express the decision information under uncertainties and its semantics is clear. The proposed model is clarified by solving the problem of evaluation and selection of sustainable innovative energy technologies. Computational results demonstrate that the model can deal with various uncertainties of the problem. Finally, the model is compared with existing techniques and extended to the case when the semantics of terms are represented by trapezoidal fuzzy numbers.展开更多
Hedging, referring to the use of various lexical and syntactic features modifying and mitigating propositions and claims, is extensively employed in effective academic writing. However, the use of hedges seems to be q...Hedging, referring to the use of various lexical and syntactic features modifying and mitigating propositions and claims, is extensively employed in effective academic writing. However, the use of hedges seems to be quite problematic for lots of Chinese ESL learners. In view of the situation, this study explores the use of hedges in academic abstracts by a group of undergraduate English majors in a university in Hainan Province. After analyzing data from a corpus and interviews, several problems have been found in the use of hedging devices of these students, and relevant implications have been drawn to the teaching of hedging in the context, which can help the students produce more effective academic writing and to achieve greater university success.展开更多
This paper investigates the evolutionary change in the OF(OF) of hedges in different moves of EMRAs(EMRAs).Two corpora are established for longitudinal study,with Corpus A consisting of EMRAs from 1990-1994 and Corpus...This paper investigates the evolutionary change in the OF(OF) of hedges in different moves of EMRAs(EMRAs).Two corpora are established for longitudinal study,with Corpus A consisting of EMRAs from 1990-1994 and Corpus B from 2005-2009.Generally,no significant change has been found in overall use of hedges.However,apart from move 6,7 and 10,we have found some interesting changes in the other moves.On the one hand,the OF of hedges in move 1,move 3,move 4 and move 5 shows a significant increase.On the other hand,the OF of hedges in move 2,8,9 and move 11 show a significant decrease.展开更多
Global extreme hydrological events pose considerable challenges to the sustainable development of human society and river ecology.Land use/cover change(LUCC)is a visible manifestation of human activity and has caused ...Global extreme hydrological events pose considerable challenges to the sustainable development of human society and river ecology.Land use/cover change(LUCC)is a visible manifestation of human activity and has caused substantial alterations in extreme hydrological regimes across rivers worldwide.The Jinsha River lies upstream of the Yangtze River and its hydrological variability has had profound socioeconomic and environmental effects.In this study,we developed Hydrological Simulation Program–FORTRAN(HSPF)and land-use simulation models of the entire watershed to simulate the effects of LUCC on hydrological extremes and quantify the inter-relationships among them.The main land-use changes between 1995 and 2015 were those associated with cropland,forest land,and grassland.Between 2015 and 2030,it is estimated that the coverage of forest land,grassland,construction land,and unused land will increase by 0.64%,0.18%,69.38%,and 45.08%,respectively,whereas that of cropland,water bodies,and snow-and ice-covered areas will decline by 8.02%,2.63%,and 0.89%,respectively.LUCC has had irregular effects on different hydrological regimes and has most severely altered stream flows.The responses of hydrological extremes to historical land-use change were characterized by spatial variation.Extreme low flows increased by 0.54%–0.59%whereas extreme high flows increased by 0%–0.08%at the lowest outlet.Responses to future land-use change will be amplified by a 0.72%–0.90%reduction in extreme low flows and a 0.08%–0.12%increase in extreme high flows.The hedging effect caused by irregular changes in tributary stream flow was found to alleviate the observed flow in mainstream rivers caused by land-use change.The extreme hydrological regimes were affected mainly by the net swap area transferred from ice and snow area to forest(NSAIF)and thereafter to cultivated land(NSAIC).Extreme low flows were found to be positively correlated with NSAIF and NSAIC,whereas extreme high flows were positively correlated with NSAIC and negatively correlated with NSAIF.展开更多
Through the application of the VAR-AGARCH model to intra-day data for three cryptocurrencies(Bitcoin,Ethereum,and Litecoin),this study examines the return and volatility spillover between these cryptocurrencies during...Through the application of the VAR-AGARCH model to intra-day data for three cryptocurrencies(Bitcoin,Ethereum,and Litecoin),this study examines the return and volatility spillover between these cryptocurrencies during the pre-COVID-19 period and the COVID-19 period.We also estimate the optimal weights,hedge ratios,and hedging effectiveness during both sample periods.We find that the return spillovers vary across the two periods for the Bitcoin–Ethereum,Bitcoin–Litecoin,and Ethereum–Litecoin pairs.However,the volatility transmissions are found to be different during the two sample periods for the Bitcoin–Ethereum and Bitcoin–Litecoin pairs.The constant conditional correlations between all pairs of cryptocurrencies are observed to be higher during the COVID-19 period compared to the pre-COVID-19 period.Based on optimal weights,investors are advised to decrease their investments(a)in Bitcoin for the portfolios of Bitcoin/Ethereum and Bitcoin/Litecoin and(b)in Ethereum for the portfolios of Ethereum/Litecoin during the COVID-19 period.All hedge ratios are found to be higher during the COVID-19 period,implying a higher hedging cost compared to the pre-COVID-19 period.Last,the hedging effectiveness is higher during the COVID-19 period compared to the pre-COVID-19 period.Overall,these findings provide useful information to portfolio managers and policymakers regarding portfolio diversification,hedging,forecasting,and risk management.展开更多
Extreme weather conditions occur at an increasing rate as evidenced by higher frequency of hurricanes and more extreme precipitation and temperature anomalies. Such extreme environmental conditions will have important...Extreme weather conditions occur at an increasing rate as evidenced by higher frequency of hurricanes and more extreme precipitation and temperature anomalies. Such extreme environmental conditions will have important implications for all living organisms through greater frequency of reproductive failure and reduced adult survival. We review examples of reproductive failure and reduced survival related to extreme weather conditions. Phenotypic plasticity may not be sufficient to allow adaptation to extreme weather for many animals. Theory predicts reduced reproductive effort as a response to increased stochasticity. We predict that patterns of natural selection will change towards truncation selection as environmental conditions become more extreme. Such changes in patterns of selection may facilitate adaptation to extreme events. However, effects of selection on reproductive effort are difficult to detect. We present a number of predictions for the effects of extreme weather conditions in need of empirical tests. Finally, we suggest a number of empirical reviews that could improve our ability to judge the effects of extreme environmental conditions on life history [Current Zoology 57 （3）： 375-389, 2011].展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11574291,61108009 and 61222504
文摘As a widely used reconstruction algorithm in quantum state tomography, maximum likelihood estimation tends to assign a rank-deficient matrix, which decreases estimation accuracy for certain quantum states. Fortunately, hedged maximum likelihood estimation （HMLE） [Phys. Rev. Lett. 105 （2010）200504] was proposed to avoid this problem. Here we study more details about this proposal in the two-qubit case and further improve its performance. We ameliorate the HMLE method by updating the hedging function based on the purity of the estimated state. Both performances of HMLE and ameliorated HMLE are demonstrated by numerical simulation and experimental implementation on the Werner states of polarization-entangled photons.
文摘This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us to investigate the connectedness at conditional quantiles.Our sample includes four major DeFi’s and six ASEAN stock markets,spanning from March 2018 to December 2022.The static results indicate a moderate level of return transmission between the system at mean and median quantile.This propagation increases substantially under extreme market conditions,establishing an asymmetric transmission across quantiles.Despite being a relatively new asset class,DeFi dominates the equity market and acts as the primary shock transmitter to the system in most instances.The dynamic analysis reveals that total system connectedness fluctuates over time and quantiles.The total system connectedness peaked during the COVID-19 and the Russia–Ukraine conflict period,indicating the impact of global events on system transmission.The optimal weight and hedge ratio estimated using the DCC-GARCH model indicate that DeFi is beneficial for portfolio construction and risk management.The rising trend in dynamic optimal weight and hedge ratio during the COVID-19 pandemic demonstrates that investors should decrease their investments in DeFi and increase hedging costs.Therefore,portfolio managers and investors should readjust their portfolio allocation in a timely manner according to different market states to build additional effective hedging and diversification strategies to avoid large losses and to reduce portfolio risk exposure.
文摘Effective management of water resources,especially groundwater,is crucial and requires a precise understanding of aquifer characteristics,imposed stresses,and the groundwater balance.Simulation-optimization models plays a vital role in guiding planners toword sustainable long-term aquifer exploita-tion.This study simulated monthly water table variations in the Kashan Plain over a ten-year period from 2008 to 2019 across 125 stress periods using the GMS model.The model was calibrated for both steady-state and transient conditions for the 2008–2016 period and validated for the 2016–2019 period.Results indicated a 4.4 m decline in groundwater levels over the 10-year study period.Given the plain's location in a arid climatic zone with limited effective precipitation for aquifer recharge,the study focused on ground-water extraction management.A modified two-point hedging policy was employed as a solution to mitigate critical groundwater depletion,reducing the annual drawdown rate from 0.44 m to 0.31 m and conserving 255 million cubic meters(mcm)of water annually.Although this approach slightly decreased reliability(i.e.the number of months meeting full water demands),it effectively minimized the risk of severe droughts and irreparable damages.This policy offers managers a dynamical and intelligent tool for regulating groundwater extraction,balancing aquifer sustainability with agricultural and urban water requirements.
文摘In this study,we propose a Gram-Charlier expansion approach to investigate the impact of skewness and kurtosis on production and hedging decisions.Consistent with the existing literature,we find that skewness and kurtosis do not affect decisions regarding optimal production;however,they significantly influence optimal hedging decisions.We observe that positive skewness with platykurtic spot prices or negative skewness with leptokurtic spot prices often leads to over-hedging when the initial forward contract price exceeds its expected value.Conversely,under-hedging is expected when the initial forward contract price falls below its expected value.In other conditions,skewness can either promote or impede speculative future trading.Using the Gram-Charlier expansion of the spot price density function,we find that optimal future positions depend on forward prices,the hedgers’risk preference,and the spot price distribution.Simulations validate our findings on the impact of skewness and kurtosis on future hedging.Finally,we analyze of a cotton storage and forward contracting dataset to illustrate the application of our methodology and support our theoretical results.
基金supported by the Foundation of Key Laboratory of System Control and Information Processing,Ministry of Education,China,Scip20240111Aeronautical Science Foundation of China,Grant 2024Z071108001the Foundation of Key Laboratory of Traffic Information and Safety of Anhui Higher Education Institutes,Anhui Sanlian University,KLAHEI18018.
文摘This paper employs the PPO(Proximal Policy Optimization) algorithm to study the risk hedging problem of the Shanghai Stock Exchange(SSE) 50ETF options. First, the action and state spaces were designed based on the characteristics of the hedging task, and a reward function was developed according to the cost function of the options. Second, combining the concept of curriculum learning, the agent was guided to adopt a simulated-to-real learning approach for dynamic hedging tasks, reducing the learning difficulty and addressing the issue of insufficient option data. A dynamic hedging strategy for 50ETF options was constructed. Finally, numerical experiments demonstrate the superiority of the designed algorithm over traditional hedging strategies in terms of hedging effectiveness.
文摘This paper examines the dependence,systemic risk spillover,return and volatility spillover,and portfolio implications across various timescales between the Green Bond(GB)and U.S.S&P 500 Stock(SP),Vanguard Total World Stock Index Fund(VT),Bitcoin(BTC),Ethereum(ETH),Ripple,OIL,and GOLD markets.The sample period is August 07,2015–October 6,2023,covering periods of instability during the COVID-19 pandemic and the Russia–Ukraine conflict.Using the wavelet–copula–conditional value-atrisk and wavelet-multivariate asymmetric-GARCH framework,our main results show that the systemic risk and return,volatility spillovers,and diversification opportunities are portfolio-specific and timescale-dependent.Specifically,there is a negative long-term correlation for the pairs GB-SP and GB-OIL,whereas the pair GB–GOLD pair is positively correlated in the short term.GB can mitigate the risk of other markets.In terms of the portfolio implications,GB weakly hedges BTC and ETH during normal and turbulent periods but has a strong ability to hedge VT in the short term and SP in the mid and long term.Regarding hedging effectiveness,the role of GB for GOLD and VT is noted.
基金The National Natural Science Foundation of China(No.61273209)the Scientific Research Foundation of Graduate School of Southeast University(No.YBJJ1528)the Scientific Innovation Research of College Graduates in Jiangsu Province(No.KYLX15-0191)
文摘A semantics-based model is proposed to enable weakened hedges, such as ＂more or less＂ and ＂roughly＂ in the context of linguistic multi-criteria decision making. First, the resemblance relations are defined based on the semantics of terms on the domain. Then, the hedges can be represented after the upper and loose upper approximations of a linguistic term are derived. Accordingly, some compact formulae can be derived for the semantics of linguistic expressions with hedges. Parameters in these formulae are objectively determined according to the semantics of original terms. The proposed model presents a more natural way to express the decision information under uncertainties and its semantics is clear. The proposed model is clarified by solving the problem of evaluation and selection of sustainable innovative energy technologies. Computational results demonstrate that the model can deal with various uncertainties of the problem. Finally, the model is compared with existing techniques and extended to the case when the semantics of terms are represented by trapezoidal fuzzy numbers.
文摘Hedging, referring to the use of various lexical and syntactic features modifying and mitigating propositions and claims, is extensively employed in effective academic writing. However, the use of hedges seems to be quite problematic for lots of Chinese ESL learners. In view of the situation, this study explores the use of hedges in academic abstracts by a group of undergraduate English majors in a university in Hainan Province. After analyzing data from a corpus and interviews, several problems have been found in the use of hedging devices of these students, and relevant implications have been drawn to the teaching of hedging in the context, which can help the students produce more effective academic writing and to achieve greater university success.
文摘This paper investigates the evolutionary change in the OF(OF) of hedges in different moves of EMRAs(EMRAs).Two corpora are established for longitudinal study,with Corpus A consisting of EMRAs from 1990-1994 and Corpus B from 2005-2009.Generally,no significant change has been found in overall use of hedges.However,apart from move 6,7 and 10,we have found some interesting changes in the other moves.On the one hand,the OF of hedges in move 1,move 3,move 4 and move 5 shows a significant increase.On the other hand,the OF of hedges in move 2,8,9 and move 11 show a significant decrease.
基金National Key Research and Development Program of China,No.2021YFC3201004。
文摘Global extreme hydrological events pose considerable challenges to the sustainable development of human society and river ecology.Land use/cover change(LUCC)is a visible manifestation of human activity and has caused substantial alterations in extreme hydrological regimes across rivers worldwide.The Jinsha River lies upstream of the Yangtze River and its hydrological variability has had profound socioeconomic and environmental effects.In this study,we developed Hydrological Simulation Program–FORTRAN(HSPF)and land-use simulation models of the entire watershed to simulate the effects of LUCC on hydrological extremes and quantify the inter-relationships among them.The main land-use changes between 1995 and 2015 were those associated with cropland,forest land,and grassland.Between 2015 and 2030,it is estimated that the coverage of forest land,grassland,construction land,and unused land will increase by 0.64%,0.18%,69.38%,and 45.08%,respectively,whereas that of cropland,water bodies,and snow-and ice-covered areas will decline by 8.02%,2.63%,and 0.89%,respectively.LUCC has had irregular effects on different hydrological regimes and has most severely altered stream flows.The responses of hydrological extremes to historical land-use change were characterized by spatial variation.Extreme low flows increased by 0.54%–0.59%whereas extreme high flows increased by 0%–0.08%at the lowest outlet.Responses to future land-use change will be amplified by a 0.72%–0.90%reduction in extreme low flows and a 0.08%–0.12%increase in extreme high flows.The hedging effect caused by irregular changes in tributary stream flow was found to alleviate the observed flow in mainstream rivers caused by land-use change.The extreme hydrological regimes were affected mainly by the net swap area transferred from ice and snow area to forest(NSAIF)and thereafter to cultivated land(NSAIC).Extreme low flows were found to be positively correlated with NSAIF and NSAIC,whereas extreme high flows were positively correlated with NSAIC and negatively correlated with NSAIF.
文摘Through the application of the VAR-AGARCH model to intra-day data for three cryptocurrencies(Bitcoin,Ethereum,and Litecoin),this study examines the return and volatility spillover between these cryptocurrencies during the pre-COVID-19 period and the COVID-19 period.We also estimate the optimal weights,hedge ratios,and hedging effectiveness during both sample periods.We find that the return spillovers vary across the two periods for the Bitcoin–Ethereum,Bitcoin–Litecoin,and Ethereum–Litecoin pairs.However,the volatility transmissions are found to be different during the two sample periods for the Bitcoin–Ethereum and Bitcoin–Litecoin pairs.The constant conditional correlations between all pairs of cryptocurrencies are observed to be higher during the COVID-19 period compared to the pre-COVID-19 period.Based on optimal weights,investors are advised to decrease their investments(a)in Bitcoin for the portfolios of Bitcoin/Ethereum and Bitcoin/Litecoin and(b)in Ethereum for the portfolios of Ethereum/Litecoin during the COVID-19 period.All hedge ratios are found to be higher during the COVID-19 period,implying a higher hedging cost compared to the pre-COVID-19 period.Last,the hedging effectiveness is higher during the COVID-19 period compared to the pre-COVID-19 period.Overall,these findings provide useful information to portfolio managers and policymakers regarding portfolio diversification,hedging,forecasting,and risk management.
文摘Extreme weather conditions occur at an increasing rate as evidenced by higher frequency of hurricanes and more extreme precipitation and temperature anomalies. Such extreme environmental conditions will have important implications for all living organisms through greater frequency of reproductive failure and reduced adult survival. We review examples of reproductive failure and reduced survival related to extreme weather conditions. Phenotypic plasticity may not be sufficient to allow adaptation to extreme weather for many animals. Theory predicts reduced reproductive effort as a response to increased stochasticity. We predict that patterns of natural selection will change towards truncation selection as environmental conditions become more extreme. Such changes in patterns of selection may facilitate adaptation to extreme events. However, effects of selection on reproductive effort are difficult to detect. We present a number of predictions for the effects of extreme weather conditions in need of empirical tests. Finally, we suggest a number of empirical reviews that could improve our ability to judge the effects of extreme environmental conditions on life history [Current Zoology 57 （3）： 375-389, 2011].
