Extreme Hot Days Research Articles

Simulation in maize–water relations: a case study for continental climate (Hungary)

AbstractLocal consequences of the global climate change in the Carpathian Basin were followed on the basis of simulated stomatal resistances. The Crop Microclimate Simulation Model of Goudriaan was applied in our study. The expected weather, plant and soil modifications were based on long‐term observations during the time period 1961–1990 in the Keszthely area (Hungary, N 46°44′, E 17°14′; altitude 112 m). Besides application of the A2 and B2 SRES scenarios, the impact of extreme hot days was also included in the study. This was necessary as these events have recently occurred more and more frequently. Demonstration of weather scenarios with relatively high warming rates was made possible by the high resolution of the model, simulating even daily changes. The stomatal resistance significantly increased in all scenarios, as was indeed experienced in the last decade (1997–2006). A twofold increase in CO2 concentration approximately halves stomatal openings even under unchanged weather conditions. This can be considered as an advantageous side effect of the global climate change on the plant's water balance, important in continental climate because of scarce precipitation. In Scenarios A2 and B2, increases in resistance were close to the effect of doubled CO2 concentration. Surprisingly, the effect of an increase in the number of extreme hot days on stomatal resistance was moderate, below than what might have been expected. The common impact of the environmental and biological factors on stomatal resistance was realized using normalized leaf area indices, where the highest increases were predicted by using the hottest and driest scenario. Moderate changes in water loss and photosynthesis indicated a certain amount of available soil moisture reserve even in the extreme weather situations in July, at Keszthely. Decrease in carbon assimilation can occur in days with extreme temperatures. Our scenarios do not include significant precipitation decline because of forecast uncertainties. A significant precipitation decrease would fundamentally reshape our results, so we do not propose to extend our conclusions in the case of significant modification in rainfall amount or distribution. Copyright © 2010 John Wiley & Sons, Ltd.

The Hungarian national climate change strategy: its principles, assignments, and a special case study on maize production

Efficient protection against global climate change requires international emission reduction measures. Before these ones are decided, the individual states should make arrangements within their own scope of authority for preventing and mitigating the adverse impacts of climate change already in progress as a consequence of carbon dioxide emissions done so far. In spring 2008 Hungary—among the very first ones in the international stage—passed a middle-term National Climate Change Strategy, which determines both the national tasks in order to reduce greenhouse gas emissions, and sectoral tasks of the adaptation to the ongoing climate change for the period of 2008–2025. As a concrete case study we investigated the possible impacts of the regional change in atmospheric carbon dioxide concentration, temperature and precipitation conditions of the Carpathian Basin on the cultivation conditions of maize, based on the downscaled IPCC 2007 scenarios. Temperatures of each scenarios increased significantly to basic run (1961–1990). This change suppressed the positive influence of elevated CO2 on carbon assimilation. Serious depression may be waited during extreme hot days at Keszthely, Hungary.

Evaluation of the Impact of an Intervention Programme on Summer Mortality in Rome

ISEE-559 Objective: Since 2001, in Rome interventions for the prevention of heat-related health effects have been in place during summer, triggered by an early heat warning system. In 2006, following guidelines of the Health Ministry, a programme of active surveillance of high risk patients by their General Practitioners (GPs) was implemented. Susceptible subjects were identified on the basis of demographic and health information retrieved from the population and hospital admission registries. Among the 2.7 million citizens of Rome, 520,000 are over 65 years, and 24,000 (4.6%) of these were identified to be at risk. Materials and Methods: Before summer, in one of the local health authorities of the city (ASL Rome E), comprising around 500,000 citizens (4650 susceptible persons), a specific information campaign for GPs was promoted to favor their collaboration. The efficacy of the intervention programme was evaluated, comparing summer mortality between the ASL Rome E and the remaining part of the city in terms of percent variation of mortality computed as percent increase of the mortality rate during extreme hot days versus mortality rate in other days. Results: A difference in the adherence of GPs to the surveillance programme was observed between the ASL Rome E (31%) and the rest of the city (8%). An increment in mortality during heat-wave days was observed in old age-groups in Rome (excluding the ASL Rome E): 75 to 84 years: +17% in males, +24% in females; 85+ years: +30% in males, +36% in females. In the ASL Rome E, the increase of mortality rate was not statistically significant and smaller than in the rest of Rome (75–84 years: +9% in males, 0% in females; 85+ years: +8% in males, +23% in females). Conclusions: These results indicate that prevention programmes including active surveillance of high risk patients can reduce heat related mortality, underlining the importance of increasing the adherence of GPs.

Extreme heat reduces and shifts United States premium wine production in the 21st century

Premium wine production is limited to regions climatically conducive to growing grapes with balanced composition and varietal typicity. Three central climatic conditions are required: (i) adequate heat accumulation; (ii) low risk of severe frost damage; and (iii) the absence of extreme heat. Although wine production is possible in an extensive climatic range, the highest-quality wines require a delicate balance among these three conditions. Although historical and projected average temperature changes are known to influence global wine quality, the potential future response of wine-producing regions to spatially heterogeneous changes in extreme events is largely unknown. Here, by using a high-resolution regional climate model forced by the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios A2 greenhouse gas emission scenario, we estimate that potential premium winegrape production area in the conterminous United States could decline by up to 81% by the late 21st century. While increases in heat accumulation will shift wine production to warmer climate varieties and/or lower-quality wines, and frost constraints will be reduced, increases in the frequency of extreme hot days (>35 degrees C) in the growing season are projected to eliminate winegrape production in many areas of the United States. Furthermore, grape and wine production will likely be restricted to a narrow West Coast region and the Northwest and Northeast, areas currently facing challenges related to excess moisture. Our results not only imply large changes for the premium wine industry, but also highlight the importance of incorporating fine-scale processes and extreme events in climate-change impact studies.

Evidence of trends in daily climate extremes over southern and west Africa

There has been a paucity of information on trends in daily climate and climate extremes, especially from developing countries. We report the results of the analysis of daily temperature (maximum and minimum) and precipitation data from 14 south and west African countries over the period 1961–2000. Data were subject to quality control and processing into indices of climate extremes for release to the global community. Temperature extremes show patterns consistent with warming over most of the regions analyzed, with a large proportion of stations showing statistically significant trends for all temperature indices. Over 1961 to 2000, the regionally averaged occurrence of extreme cold (fifth percentile) days and nights has decreased by −3.7 and −6.0 days/decade, respectively. Over the same period, the occurrence of extreme hot (95th percentile) days and nights has increased by 8.2 and 8.6 days/decade, respectively. The average duration of warm (cold) has increased (decreased) by 2.4 (0.5) days/decade and warm spells. Overall, it appears that the hot tails of the distributions of daily maximum temperature have changed more than the cold tails; for minimum temperatures, hot tails show greater changes in the NW of the region, while cold tails have changed more in the SE and east. The diurnal temperature range (DTR) does not exhibit a consistent trend across the region, with many neighboring stations showing opposite trends. However, the DTR shows consistent increases in a zone across Namibia, Botswana, Zambia, and Mozambique, coinciding with more rapid increases in maximum temperature than minimum temperature extremes. Most precipitation indices do not exhibit consistent or statistically significant trends across the region. Regionally averaged total precipitation has decreased but is not statistically significant. At the same time, there has been a statistically significant increase in regionally averaged daily rainfall intensity and dry spell duration. While the majority of stations also show increasing trends for these two indices, only a few of these are statistically significant. There are increasing trends in regionally averaged rainfall on extreme precipitation days and in maximum annual 5‐day and 1‐day rainfall, but only trends for the latter are statistically significant.

The impact of the summer 2003 heat wave in Iberia: how should we measure it?

We present a new approach to improve the reliability of quantifying the impact of a heat wave on mortality rates. We show, for the recent European summer 2003 heat wave, that the use of absolute maximum temperature values, or number of days above a given threshold, can be misleading. Here, we have assessed the impact of the heat wave on Iberian mortality by applying a four step procedure: (1) calculating, for each observatory, the local maximum temperature (T (max)) distributions, (2) calculating the corresponding 95th percentile values (T (threshold)), (3) locally defining extremely hot days (EHD) as those days on which the local threshold of the 95th percentile of the series is exceeded, and (4) calculating the total degrees-days (DD) of exceedance, by calculating the difference T (max)-T (threshold) and summing these values for all days above T (threshold). We show that the relationship between summer mortality rates and the DD index is non-linear and can be described by a logarithmic function, with a correlation coefficient of 0.78, which explains 60.6% of the mortality variance (F value of 24.64, significant at P<0.0001). Using maximum temperatures, no significant relationship is found with mortality, whereas the EHD frequency shows a significant association with mortality, albeit weaker than that obtained with DD.

Synoptic conditions leading to extremely high temperatures in Madrid

Abstract. Extremely hot days (EHD) in Madrid have been analysed to determine the synoptic patterns that produce EHDs during the period of 1955–1998. An EHD is defined as a day with maximum temperature higher than 36.5°C, a value which is the threshold for the intense effects on mortatility and it coincides with the 95 percentile of the series. Two different situations have been detected as being responsible for an EHD occurrence, one more dynamical, produced by southern fluxes, and another associated with a stagnation situation over Iberia of a longer duration. Both account for 92% of the total number of days, thus providing an efficient classification framework. A circulation index has been derived to characterise and forecast an EHD occurrence. This paper shows that EHD occur in Madrid during short duration events, and no long heat waves, like those recorded in other cities, are present. Additionally, no clear pattern can be detected in the EHD frequency; the occurrence is tied to changes in the summer location of the Azores high.Key words. Meteorology and atmospheric dynamics (Climatology; synoptic-scale meteorology; general or miscellaneous)

Characteristics of Daily and Extreme Temperatures over Canada

Recent studies have shown that, since 1900, mean annual temperature over southern Canada has increased by an average of 0.9°C, with the largest warming during winter and early spring. Every season was associated with greater increases in minimum temperature as opposed to maximum, thus resulting in a significant decrease in the daily temperature range (DTR). The second half of the twentieth century was associated with significant winter and spring warming in the south and west, and cooling in the northeast. However, no significant changes in DTR were observed during this period. This investigation goes beyond the annual/seasonal scales by examining trends and variability in daily minimum and maximum temperature with particular emphasis on extremes. Using recently updated, homogenized daily data, spatial and temporal characteristics of daily and extreme temperature-related variables are analyzed on a seasonal basis for the periods of 1900–98 (southern Canada), and 1950–98 (the entire country). From 1900 to 1998, the majority of southern Canada shows significantly increasing trends to the lower and higher percentiles of the daily minimum and maximum temperature distribution. The findings translate into fewer days with extreme low temperature during winter, spring, and summer and more days with extreme high temperature during winter and spring. No consistent trends are found for the higher percentiles of summer daily maximum temperature, indicating little change to the number of extreme hot summer days. Over the southwest, increases are larger to the left-hand side of the daily minimum and maximum temperature distribution, resulting in significant decreases to the intraseasonal standard deviation of daily temperature. The 1950–98 results are somewhat different from the entire century, especially, during winter and spring. This result includes significant increases to the low and high percentiles over the west, and decreases over the east. This analysis reveals that the largest individual daily temperature trends (both minimum and maximum) occur during winter and early spring, when substantial warming is observed. For summer, increases are only associated with daily minimum temperature. Autumn displays varying results, with some late season cooling, mainly over western regions. The observed warming trends have a substantial effect on several economically sensitive indices. This effect includes significant increases in the number of growing and cooling degree days and significant decreases in heating degree days. In addition, the length of the frost-free period is significantly longer over most of the country.