•Simulated heat waves were applied to field-grown maize using infrared heating technology.•Heat waves during vegetative growth did not affect reproductive biomass.•Heat waves during silking ...significantly reduced reproductive biomass.•Leaf water potential and photosynthesis transiently decreased during heat waves.•High temperature stress likely affected reproductive structures to reduce yield.
Due to climate change, heat waves are predicted to become more frequent and severe. While long-term studies on temperature stress have been conducted on important crops such as maize (Zea mays), the immediate or long-term effects of short duration but extreme high temperature events during key developmental periods on physiological and yield parameters are unknown. Therefore, heat waves were applied to field-grown maize in east central Illinois using infrared heating technology. The heat waves warmed the canopy approximately 6°C above ambient canopy temperatures for three consecutive days during vegetative development (Wv1) and during an early reproductive stage (silking; Wv2). Neither treatment affected aboveground vegetative biomass, and Wv1 did not significantly reduce reproductive biomass. However, Wv2 significantly reduced total reproductive biomass by 16% (p<0.1) due to significant reductions in cob length (p<0.1), cob mass (p<0.05), and husk mass (p<0.05). Although not statistically significant, seed yield was also reduced by 13% (p=0.15) and kernel number by 10% (p=0.16) in the Wv2 treatment. Soil water status was unaffected in both treatments, and leaf water potential and midday photosynthesis were only transiently reduced by heating with complete recovery after the treatment period. Therefore, the reduction in Wv2 reproductive biomass was most likely due to greater sensitivity of reproductive structures to direct effects of high temperature stress.
The Yangtze River valley (YRV), located in central-eastern China, has witnessed increased numbers of heat waves in the summer since 1951. Knowing what factors control and affect the interannual ...variability of heat waves, especially distinguishing the contributions of anomalous sea surface temperature (SST) forcings and those of internal modes of variability, is important to improving heat wave prediction. After evaluating 70 members of the atmospheric model intercomparison project (AMIP) experiments from the 25 models that participated in the coupled model intercomparison project phase 5 (CMIP5), 13 high-skill members (HSMs) are selected to estimate the SST-forced variability. The results show that approximately 2/3 of the total variability of the July–August heat waves in the YRV during 1979–2008 can be attributed to anomalous SST forcings, whereas the other 1/3 are due to internal variability. Within the SST-forced component, one-half of the influence is from the impact of the El Niño–Southern Oscillation (ENSO) and the other half is from non-ENSO related SST forcings, specifically, the SST anomalies in the North Pacific and the North Atlantic. Both the decaying El Niño and developing La Niña accompanied by a warm Indian Ocean and cold central Pacific, respectively, are favorable to hotter summers in the YRV because these patterns strengthen and extend the western North Pacific Subtropical High (WNPSH) westwards, for which the decaying ENSO plays a dominant role. The internal variability shows a circumglobal teleconnection in which Rossby waves propagate southeastwards over the Eurasian Continent and strengthen the WNPSH. Atmospheric model sensitivity experiments confirm that non-ENSO SST forcings can modulate the WNPSH and heat wave variability by projecting their influences onto the internal mode.
•Urban Overheating affects energy generation and demand, pollution, health and vulnerability.•It increases the energy demand for cooling and decreases the efficiency of power plants.•Rises the ...concentration of ground level ozone.•Increase indoor temperature in low income housing.•Increases heat related mortality and morbidity.
Urban overheating is documented for more than 400 major cities in the world. Numerous experimental data show that the magnitude of the average temperature increase may exceed 4-5 C, while at the peak may exceed 10 C. Increased ambient temperatures cause a serious impact on the cooling energy consumption, peak electricity demand, heat related mortality and morbidity, urban environmental quality, local vulnerability and comfort. Synergies between urban heat island and heat waves increase further the amplitude of urban overheating The present paper reviews and reports the recent progress and knowledge on the specific impact of current and projected urban overheating in energy, peak electricity demand, air quality, mortality and morbidity and urban vulnerability. In parallel, it discusses new findings related to the characteristics and the magnitude of urban overheating, and reports and analyse the recent knowledge on the synergies between urban heat island and heat waves.
SUMMARY
Global warming and climate change are driving an alarming increase in the frequency and intensity of different abiotic stresses, such as droughts, heat waves, cold snaps, and flooding, ...negatively affecting crop yields and causing food shortages. Climate change is also altering the composition and behavior of different insect and pathogen populations adding to yield losses worldwide. Additional constraints to agriculture are caused by the increasing amounts of human‐generated pollutants, as well as the negative impact of climate change on soil microbiomes. Although in the laboratory, we are trained to study the impact of individual stress conditions on plants, in the field many stresses, pollutants, and pests could simultaneously or sequentially affect plants, causing conditions of stress combination. Because climate change is expected to increase the frequency and intensity of such stress combination events (e.g., heat waves combined with drought, flooding, or other abiotic stresses, pollutants, and/or pathogens), a concentrated effort is needed to study how stress combination is affecting crops. This need is particularly critical, as many studies have shown that the response of plants to stress combination is unique and cannot be predicted from simply studying each of the different stresses that are part of the stress combination. Strategies to enhance crop tolerance to a particular stress may therefore fail to enhance tolerance to this specific stress, when combined with other factors. Here we review recent studies of stress combinations in different plants and propose new approaches and avenues for the development of stress combination‐ and climate change‐resilient crops.
Significance Statement
Climate change and global warming increase the likelihood that trees and crop plants will be subjected to a combination of different abiotic and biotic stresses, compromising global food production and security. This paper reviews recent advances in the study of plant responses to stress combinations and proposes potential strategies to develop crops with high resilience to a wide range of stress factors and their combination.
Over Yangtze River valley (YRV) where heat wave (HW) events most frequently occur in China during 1979–2014, 30 out of 57 HW events (nearly 55%) in July and August is found to be related with the dry ...phases of atmospheric quasi-biweekly oscillation (QBWO). When a significant low-level anticyclonic anomaly (LAA) associated with QBWO appears over YRV, temperature rises sharply according to the adiabatic heating caused by subsidence and the enhanced downward solar radiation due to decreased clouds. The LAA with subsidence over YRV is primarily generated by quasi-biweekly atmospheric waves, which are classified to three types through case-by-case categorization, named as “mid-latitude wavetrain”, “WNP (western North Pacific) wavetrain” and “double wavetrains”, respectively. The mid-latitude wavetrain QBWO causes the LAA through subsidence induced by upper-level cyclonic vorticity which is associated with an eastward/southeastward migrating wave train from Eastern Europe to WNP in the upper troposphere. The WNP wavetrain QBWO forms LAA through a northwestward migrating lower-tropospheric wave train emanating from tropical WNP to southeastern China. The double wavetrains QBWO triggers LAA through both the low-level shear anticyclonic vorticity provided by a low-level northwestward/westward propagating wave train from tropical WNP to South China Sea and the upper-level positive vorticity associated with an eastward/southeastward migrating wave train from Eastern Europe to southeastern China in the upper troposphere. In all cases, South Asian High extends eastward and WNP subtropical high extends westward during HW events. Tracing these distinct precursory circulation anomalies may facilitate better understanding and short-medium range forecast of HW.
Climate extremes such as heat waves and droughts are projected to occur more frequently with increasing temperature and an intensified hydrological cycle. It is important to understand and quantify ...how forest carbon fluxes respond to heat and drought stress. In this study, we developed a series of daily indices of sensitivity to heat and drought stress as indicated by air temperature (Ta) and evaporative fraction (EF). Using normalized daily carbon fluxes from the FLUXNET Network for 34 forest sites in North America, the seasonal pattern of sensitivities of net ecosystem productivity (NEP), gross ecosystem productivity (GEP) and ecosystem respiration (RE) in response to Ta and EF anomalies were compared for different forest types. The results showed that warm temperatures in spring had a positive effect on NEP in conifer forests but a negative impact in deciduous forests. GEP in conifer forests increased with higher temperature anomalies in spring but decreased in summer. The drought‐induced decrease in NEP, which mostly occurred in the deciduous forests, was mostly driven by the reduction in GEP. In conifer forests, drought had a similar dampening effect on both GEP and RE, therefore leading to a neutral NEP response. The NEP sensitivity to Ta anomalies increased with increasing mean annual temperature. Drier sites were less sensitive to drought stress in summer. Natural forests with older stand age tended to be more resilient to the climate stresses compared to managed younger forests. The results of the Classification and Regression Tree analysis showed that seasons and ecosystem productivity were the most powerful variables in explaining the variation of forest sensitivity to heat and drought stress. Our results implied that the magnitude and direction of carbon flux changes in response to climate extremes are highly dependent on the seasonal dynamics of forests and the timing of the climate extremes.
A series of daily indices of forest sensitivity to heat and drought stress was developed using carbon flux and meteorological data from the FLUXNET Network for 34 forest sites having long‐term measurements in North. The seasonal pattern of sensitivities of net ecosystem productivity, gross ecosystem productivity, and ecosystem respiration in response to air temperature and evaporative fraction anomalies vary among different forest types. The magnitude and direction of carbon flux changes in response to climate extremes are highly dependent on seasonal dynamics of forests and the timing of the climate extremes.
The Summer East Atlantic (SEA) mode is the second dominant mode of summer low‐frequency variability in the Euro‐Atlantic region. Using reanalysis data, we show that SEA‐related circulation anomalies ...significantly influence temperatures and precipitation over Europe. We present evidence that part of the interannual SEA variability is forced by diabatic heating anomalies of opposing signs in the tropical Pacific and Caribbean that induce an extratropical Rossby wave train. This precipitation dipole is related to SST anomalies characteristic of the developing El Niño–Southern Oscillation phases. Seasonal hindcast experiments forced with observed sea surface temperatures (SSTs) exhibit skill at capturing the interannual SEA variability corroborating the proposed mechanism and highlighting the possibility for improved prediction of boreal summer variability. Our results indicate that tropical forcing of the SEA likely played a role in the dynamics of the 2015 European heat wave.
Key Points
Identification of a second mode of summer variability in the Euro‐Atlantic sector, called the SEA
The SEA mode is forced by tropical diabatic heating anomalies related to the developing ENSO phase
This tropical‐extratropical teleconnection likely played a role in the 2015 European summer heat wave
Summary
With climate change, heat waves are becoming increasingly frequent, intense and broader in spatial extent. However, while the lethal effects of heat waves on humans are well documented, the ...impacts on flora are less well understood, perhaps except for crops. We summarize recent findings related to heat wave impacts including: sublethal and lethal effects at leaf and plant scales, secondary ecosystem effects, and more complex impacts such as increased heat wave frequency across all seasons, and interactions with other disturbances. We propose generalizable practical trials to quantify the critical bounding conditions of vulnerability to heat waves. Collectively, plant vulnerabilities to heat waves appear to be underappreciated and understudied, particularly with respect to understanding heat wave driven plant die‐off and ecosystem tipping points.
The mortality cost of carbon Bressler, R. Daniel
Nature communications,
07/2021, Volume:
12, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
Many studies project that climate change can cause a significant number of excess deaths. Yet, in integrated assessment models (IAMs) that determine the social cost of carbon (SCC) and ...prescribe optimal climate policy, human mortality impacts are limited and not updated to the latest scientific understanding. This study extends the DICE-2016 IAM to explicitly include temperature-related mortality impacts by estimating a climate-mortality damage function. We introduce a metric, the mortality cost of carbon (MCC), that estimates the number of deaths caused by the emissions of one additional metric ton of CO2. In the baseline emissions scenario, the 2020 MCC is 2.26 × 10
‒4
low to high estimate −1.71× 10
‒4
to 6.78 × 10
‒4
excess deaths per metric ton of 2020 emissions. This implies that adding 4,434 metric tons of carbon dioxide in 2020—equivalent to the lifetime emissions of 3.5 average Americans—causes one excess death globally in expectation between 2020-2100. Incorporating mortality costs increases the 2020 SCC from $37 to $258 −$69 to $545 per metric ton in the baseline emissions scenario. Optimal climate policy changes from gradual emissions reductions starting in 2050 to full decarbonization by 2050 when mortality is considered.
PDF
