Human contribution to the European heatwave of 2003

Heat waves and heat days in an arid city in the northwest of México: current trends and in climate change scenarios

The aim of this work is to study heat waves (HWs) in Mexicali, Mexico, because numerous deaths have been reported in this city, caused by heatstroke. This research acquires relevancy because several studies have projected that the health impacts of HWs could increase under various climate change scenarios, especially in countries with low adaptive capacity, as is our case. This paper has three objectives: first, to analyze the observed change in the summer (1 June to 15 September) daily maximum temperature during the period from 1951 to 2006; secondly, to characterize the annual and monthly evolution of frequency, duration and intensity of HWs; and finally, to generate scenarios of heat days (HDs) by means of a statistical downscaling model, in combination with a global climate model (HadCM3), for the 2020 s, 2050 s, and 2080 s. The results show summer maximum temperatures featured warming and cooling periods from 1951 until the mid-1980s and, later, a rising tendency, which prevailed until 2006. The duration and intensity of HWs have increased for all summer months, which is an indicator of the severity of the problem; in fact, there are 2.3 times more HWs now than in the decade of the 1970s. The most appropriate distribution for modeling the occurrence of HDs was the Weibull, with the maximum temperature as co-variable. For the 2020 s, 2050 s, and 2080 s, HDs under a medium-high emissions scenario (A2) could increase relative to 1961-1990, by 2.1, 3.6, and 5.1 times, respectively, whereas under a medium-low emissions scenario (B2), HDs could increase by 2.4, 3.4, and 4.0, for the same projections of time.

Comparison between two methods of defining heat waves: a retrospective study in Castile-La Mancha (Spain)

INTRODUCTION

Following the 2003 heat wave, many European countries implemented heat-wave prevention plans. A number of aspects can prove fundamental in determining the effectiveness of such plans, and of these we sought to analyse the criteria used to define threshold temperatures and trigger a higher level of intervention.

METHOD

Retrospective study of the days on which heat-wave thresholds were exceeded during the period 1974-2003 was conducted. We compared when and at what level the heat-wave prevention plan would have been activated using a statistical-meteorological criterion (as applied by the Spanish Ministry of Health & Consumer Affairs) versus a temperature-mortality criterion.

RESULTS

The number of days on which the threshold was exceeded was far higher when the temperature-mortality criterion was applied. The temperature percentile at which a heat wave occurred was different for each province analysed and was inversely proportional to its respective ageing index. Using both criteria, there was an increase in heat-wave days per decade.

CONCLUSION

The establishment of a heat-wave threshold temperature must be based on knowledge of the cause-effect relationship between temperature and the health of a given population. Mortality is an appropriate indicator of population health. The future effects of climate change render it essential for this relationship to be studied on a local scale, so as to enable truly efficient prevention plans to be drawn up.

Current and future climate- and air pollution-mediated impacts on human health

BACKGROUND

We describe a project to quantify the burden of heat and ozone on mortality in the UK, both for the present-day and under future emission scenarios.

METHODS

Mortality burdens attributable to heat and ozone exposure are estimated by combination of climate-chemistry modelling and epidemiological risk assessment. Weather forecasting models (WRF) are used to simulate the driving meteorology for the EMEP4UK chemistry transport model at 5 km by 5 km horizontal resolution across the UK; the coupled WRF-EMEP4UK model is used to simulate daily surface temperature and ozone concentrations for the years 2003, 2005 and 2006, and for future emission scenarios. The outputs of these models are combined with evidence on the ozone-mortality and heat-mortality relationships derived from epidemiological analyses (time series regressions) of daily mortality in 15 UK conurbations, 1993-2003, to quantify present-day health burdens.

RESULTS

During the August 2003 heatwave period, elevated ozone concentrations > 200 microg m-3 were measured at sites in London and elsewhere. This and other ozone photochemical episodes cause breaches of the UK air quality objective for ozone. Simulations performed with WRF-EMEP4UK reproduce the August 2003 heatwave temperatures and ozone concentrations. There remains day-to-day variability in the high ozone concentrations during the heatwave period, which on some days may be explained by ozone import from the European continent.Preliminary calculations using extended time series of spatially-resolved WRF-EMEP4UK model output suggest that in the summers (May to September) of 2003, 2005 & 2006 over 6000 deaths were attributable to ozone and around 5000 to heat in England and Wales. The regional variation in these deaths appears greater for heat-related than for ozone-related burdens.Changes in UK health burdens due to a range of future emission scenarios will be quantified. These future emissions scenarios span a range of possible futures from assuming current air quality legislation is fully implemented, to a more optimistic case with maximum feasible reductions, through to a more pessimistic case with continued strong economic growth and minimal implementation of air quality legislation.

CONCLUSION

Elevated surface ozone concentrations during the 2003 heatwave period led to exceedences of the current UK air quality objective standards. A coupled climate-chemistry model is able to reproduce these temperature and ozone extremes. By combining model simulations of surface temperature and ozone with ozone-heat-mortality relationships derived from an epidemiological regression model, we estimate present-day and future health burdens across the UK. Future air quality legislation may need to consider the risk of increases in future heatwaves.

Climate change and vector-borne diseases

In this review we examine formally the conditions under which vector-borne diseases are likely to change, and the directions of those changes, under various scenarios of climate change. We specify the criteria that must be met in order to conclude that climate change is having an effect on vector-borne diseases. We then take several examples from the literature and show how some of them meet these criteria, while others do not. For those that do not, there are alternative explanations that involve much more plausible drivers of the recorded changes in the diseases concerned.

Coping with commitment: projected thermal stress on coral reefs under different future scenarios

BACKGROUND

Periods of anomalously warm ocean temperatures can lead to mass coral bleaching. Past studies have concluded that anthropogenic climate change may rapidly increase the frequency of these thermal stress events, leading to declines in coral cover, shifts in the composition of corals and other reef-dwelling organisms, and stress on the human populations who depend on coral reef ecosystems for food, income and shoreline protection. The ability of greenhouse gas mitigation to alter the near-term forecast for coral reefs is limited by the time lag between greenhouse gas emissions and the physical climate response.

METHODOLOGY/PRINCIPAL FINDINGS

This study uses observed sea surface temperatures and the results of global climate model forced with five different future emissions scenarios to evaluate the "committed warming" for coral reefs worldwide. The results show that the physical warming commitment from current accumulation of greenhouse gases in the atmosphere could cause over half of the world's coral reefs to experience harmfully frequent (p> or =0.2 year(-1)) thermal stress by 2080. An additional "societal" warming commitment, caused by the time required to shift from a business-as-usual emissions trajectory to a 550 ppm CO(2) stabilization trajectory, may cause over 80% of the world's coral reefs to experience harmfully frequent events by 2030. Thermal adaptation of 1.5 degrees C would delay the thermal stress forecast by 50-80 years.

CONCLUSIONS/SIGNIFICANCE

The results suggest that adaptation -- via biological mechanisms, coral community shifts and/or management interventions -- could provide time to change the trajectory of greenhouse gas emissions and possibly avoid the recurrence of harmfully frequent events at the majority (97%) of the world's coral reefs this century. Without any thermal adaptation, atmospheric CO(2) concentrations may need to be stabilized below current levels to avoid the degradation of coral reef ecosystems from frequent thermal stress events.

Climate change and malaria in Canada: a systems approach

This article examines the potential for changes in imported and autochthonous malaria incidence in Canada as a consequence of climate change. Drawing on a systems framework, we qualitatively characterize and assess the potential direct and indirect impact of climate change on malaria in Canada within the context of other concurrent ecological and social trends. Competent malaria vectors currently exist in southern Canada, including within this range several major urban centres, and conditions here have historically supported endemic malaria transmission. Climate change will increase the occurrence of temperature conditions suitable for malaria transmission in Canada, which, combined with trends in international travel, immigration, drug resistance, and inexperience in both clinical and laboratory diagnosis, may increase malaria incidence in Canada and permit sporadic autochthonous cases. This conclusion challenges the general assumption of negligible malaria risk in Canada with climate change.

Climate change and heat-related mortality in six cities Part 2: climate model evaluation and projected impacts from changes in the mean and variability of temperature with climate change

Previous assessments of the impacts of climate change on heat-related mortality use the "delta method" to create temperature projection time series that are applied to temperature-mortality models to estimate future mortality impacts. The delta method means that climate model bias in the modelled present does not influence the temperature projection time series and impacts. However, the delta method assumes that climate change will result only in a change in the mean temperature but there is evidence that there will also be changes in the variability of temperature with climate change. The aim of this paper is to demonstrate the importance of considering changes in temperature variability with climate change in impacts assessments of future heat-related mortality. We investigate future heat-related mortality impacts in six cities (Boston, Budapest, Dallas, Lisbon, London and Sydney) by applying temperature projections from the UK Meteorological Office HadCM3 climate model to the temperature-mortality models constructed and validated in Part 1. We investigate the impacts for four cases based on various combinations of mean and variability changes in temperature with climate change. The results demonstrate that higher mortality is attributed to increases in the mean and variability of temperature with climate change rather than with the change in mean temperature alone. This has implications for interpreting existing impacts estimates that have used the delta method. We present a novel method for the creation of temperature projection time series that includes changes in the mean and variability of temperature with climate change and is not influenced by climate model bias in the modelled present. The method should be useful for future impacts assessments. Few studies consider the implications that the limitations of the climate model may have on the heat-related mortality impacts. Here, we demonstrate the importance of considering this by conducting an evaluation of the daily and extreme temperatures from HadCM3, which demonstrates that the estimates of future heat-related mortality for Dallas and Lisbon may be overestimated due to positive climate model bias. Likewise, estimates for Boston and London may be underestimated due to negative climate model bias. Finally, we briefly consider uncertainties in the impacts associated with greenhouse gas emissions and acclimatisation. The uncertainties in the mortality impacts due to different emissions scenarios of greenhouse gases in the future varied considerably by location. Allowing for acclimatisation to an extra 2 degrees C in mean temperatures reduced future heat-related mortality by approximately half that of no acclimatisation in each city.

Quantifying sources and sinks of trace gases using space-borne measurements: current and future science

We have been observing the Earth's upper atmosphere from space for several decades, but only over the past decade has the necessary technology begun to match our desire to observe surface air pollutants and climate-relevant trace gases in the lower troposphere, where we live and breathe. A new generation of Earth-observing satellites, capable of probing the lower troposphere, are already orbiting hundreds of kilometres above the Earth's surface with several more ready for launch or in the planning stages. Consequently, this is one of the most exciting times for the Earth system scientists who study the countless current-day physical, chemical and biological interactions between the Earth's land, ocean and atmosphere. First, I briefly review the theory behind measuring the atmosphere from space, and how these data can be used to infer surface sources and sinks of trace gases. I then present some of the science highlights associated with these data and how they can be used to improve fundamental understanding of the Earth's climate system. I conclude the paper by discussing the future role of satellite measurements of tropospheric trace gases in mitigating surface air pollution and carbon trading.

[Medical consequences of global warming]

INTRODUCTION

The global warming of the planet and its anthropogenic origin are no longer debatable. Nevertheless, from a medical point of view, while the epidemiological consequences of the warming are rather well-known, the biological consequences are still poorly documented. This is a good example of evolutionary (or darwinian) medicine.

METHODS

The research strategy of this systematic review is based on both PubMed during the period of 2000-2007 and several reviews articles for the period >2000.

RESULTS

From a medical point of view, there are four types of consequences. 1-The simple elevation of the average external temperature is accompanied by an increased global mortality and morbidity, the mortality/external temperature is a J curve, with the warm branch more pronounced than the cold one. A recent study on 50 different cities had confirmed that global, and more specifically cardiovascular mortalities were enhanced at the two extreme of the temperatures. 2-The acute heatwaves, such as that which happened in France in August 2003, have been studied in detail by several groups. The mortality which was observed during the recent heatwaves was not compensated by harvesting, strongly suggesting that we were dealing with heat stroke, and that such an increased mortality was more reflecting the limits of our adaptational capacities than aggravation of a previously altered health status. 3-Climate changes have modified the repartition and virulence of pathogenic agents (dengue, malaria...) and above all their vectors. Such modifications were exponential and are likely to reflect the biological properties of parasites. 4-Indirect consequences of global warming include variations in the hydraulic cycle, the new form of tropical hurricanes and many different changes affecting both biodiversity and ecosystems. They will likely result in an increased level of poverty.

DISCUSSION

These finding gave rise to several basic biological questions, rarely evoked, and that concern the limits of the adaptational capacities of human genome. Our genome has indeed been shaped in the past by a rather cold environment which has acutely been modified. The immediate physiological regulation includes sweating and skin vasodilatation. The latter may strongly enhance the cardiac output which explains the heat-induced cardiac decompensation. Long term regulation depends upon the numerous mechanisms of uncoupling of the mitochondrial respiration. For the moment, the thermolytic mechanisms and their regulation were rather poorly documented.

A method for computing the fraction of attributable risk related to climate damages

The recent decision of the U.S. Supreme Court on the regulation of CO2 emissions from new motor vehicles shows the need for a robust methodology to evaluate the fraction of attributable risk from such emissions. The methodology must enable decisionmakers to reach practically relevant conclusions on the basis of expert assessments the decisionmakers see as an expression of research in progress, rather than as knowledge consolidated beyond any reasonable doubt. This article presents such a methodology and demonstrates its use for the Alpine heat wave of 2003. In a Bayesian setting, different expert assessments on temperature trends and volatility can be formalized as probability distributions, with initial weights (priors) attached to them. By Bayesian learning, these weights can be adjusted in the light of data. The fraction of heat wave risk attributable to anthropogenic climate change can then be computed from the posterior distribution. We show that very different priors consistently lead to the result that anthropogenic climate change has contributed more than 90% to the probability of the Alpine summer heat wave in 2003. The present method can be extended to a wide range of applications where conclusions must be drawn from divergent assessments under uncertainty.

Rates of urbanisation and the resiliency of air and water quality

Global human population and urban development are increasing at unprecedented rates and creating tremendous stress on local, regional, and global air and water quality. However, little is known about how urban areas vary in their capacity to address effectively air and water quality impacts associated to urban development. There exists a need to better understanding the factors that mediate the interactions between urbanisation and variations of environmental quality. By synthesizing literatures on the relationship between urban development and air and water quality, we assess the amount of scholarship for each of these cities, characterize population growth rates in one hundred of the largest global cities, and link growth trends to changes in air and water quality. Our results suggest that, while there is a growing literature linking urbanisation and environmental quality, some regions of the globe are better represented than others, and that these trends are consistent with our characterization of population growth rates. In addition, the comparison between population growth rates and air and water quality suggest that multiple factors affect the environmental quality, and that approaching rates of urbanisation through the lens of 'resiliency' can be an effective integrative concept for studying the capacity of urban areas to respond to rapid rates of change. Based on these results we offer a framework for systematically assessing changes in air and water quality in megacities.

The effect of temperature on mortality in Stockholm 1998--2003: a study of lag structures and heatwave effects

AIMS

To describe seasonal patterns of natural mortality in Stockholm as well as the temperature-mortality relationship and the lag structure for effects of high and low temperatures; to describe the impact of high temperatures on cardiovascular and respiratory mortality, and the general effect of high temperatures in different age groups; and to investigate whether there is any indication of an additional heatwave or cold spell effect.

METHODS

Generalized additive Poisson regression models were fitted to mortality and temperature data from Stockholm from the period 1998-2003, controlling for influenza, season, time trends, week day, and holidays.

RESULTS

The mortality in Stockholm followed a seasonal pattern, with a peak in the winter season. The ;;optimal temperature'' was around 11-12 degrees C. Above this temperature, the cumulative general relative risk (RR) corresponded to a 1.4% (95% confidence interval (CI)=0.8-2.0) increase per degrees C, and below this temperature the cumulative RR corresponded to a 0.7% (95% CI=0.5-0.9) decrease per degrees C. Age-specific RRS were estimated above the threshold for age <65 years, age 65-74 years, and age >74 years, with estimated increases of 0.5% (not significant), 1.5% (not significant) and 1.6% (95% CI=0.9-2.3) per degrees C, respectively. The RRs for cardiovascular and respiratory causes were studied above the breakpoint, and estimated to be 1.1% (95% CI=0.3-2.0) and 4.3% (95% CI=2.2-6.5) per degrees C, respectively. The lag structures from moving averages and polynomial distributed lag models coincided with a rather direct effect during summer (lag 0 and 1) and a more prolonged effect during winter, covering about a week. The inclusion of an indicator of heatwaves added an increase in daily mortality of 3.1-7.7%, depending on the threshold.

CONCLUSIONS

These results show that the predicted increase in heat events must also be taken seriously in Scandinavia, whatever the extent of the decreasing cold related mortality. The relative risks associated with heat and heatwaves seem stronger than the cold effects and thus a larger public health threat, since northern populations have not yet adapted to heat as have been done over a long time for the cold periods. The pressure on the healthcare sector will probably increase in the warm season, periodically it may become even greater than the pressure due to cold weather, which will be a new phenomenon for the healthcare sector to cope with. We need to be prepared for these kind of events by developing adaptation and education strategies to handle the consequences that a warmer climate will have for public health and the healthcare sector.

Interaction between amino acid neurotransmitters and opioid receptors in hyperthermia-induced brain pathology

This review is focused on the possible interaction between amino acid neurotransmitters and opioid receptors in hyperthermia-induced brain dysfunction. A balance between excitatory and inhibitory amino acids appears to be necessary for normal brain function. Increased excitotoxicity and a decrease in inhibitory amino acid neurotransmission in hyperthermia are associated with brain pathology and cognitive impairment. This is supported by recent data from our laboratory that show a marked increase in glutamate and aspartate and a decrease in GABA and glycine in several brain areas following heat stress at the time of brain pathology. Blockade of multiple opioid receptors with naloxone restored the heat stress-induced decline in GABA and glycine and thwarted the elevation of glutamate and aspartate in the CNS. In naloxone-treated stressed animals, cognitive dysfunction and brain pathology are largely absent. Taken together, these new findings suggest that an intricate balance between excitatory and inhibitory amino acids is important for brain function in heat stress. In addition, opioid receptors play neuromodulatory roles in amino acid neurotransmission in hyperthermia.

Heat stroke and cytokines

Heat stroke is a life-threatening illness that affects all segments of society, including the young, aged, sick, and healthy. The recent high death toll in France (Dorozynski, 2003) and the death of high-profile athletes has increased public awareness of the adverse effects of heat injury. However, the etiology of the long-term consequences of this syndrome remains poorly understood such that preventive/treatment strategies are needed to mitigate its debilitating effects. Cytokines are important modulators of the acute phase response (APR) to stress, infection, and inflammation. Current data implicating cytokines in heat stroke responses are mainly from correlation studies showing elevated plasma levels in heat stroke patients and experimental animal models. Correlation data fall far short of revealing the mechanisms of cytokine actions such that additional research to determine the role of these endogenous substances in the heat stroke syndrome is required. Furthermore, cytokine determinations have occurred mainly at end-stage heat stroke, such that the role of these substances in progression and long-term recovery is poorly understood. Despite several studies implicating cytokines in heat stroke pathophysiology, few studies have examined the protective effect(s) of cytokine antagonism on the morbidity and mortality of heat stroke. This is particularly surprising since heat stroke responses resemble those observed in the endotoxemic syndrome, for which a role for endogenous cytokines has been strongly implicated. The implication of cytokines as mediators of endotoxemia and the presence of circulating endotoxin in heat stroke patients suggests that much knowledge can be gained from applying our current understanding of endotoxemic pathophysiology to the study of heat stroke. Heat shock proteins (HSPs) are highly conserved proteins that function as molecular chaperones for denatured proteins and reciprocally modulate cytokine production in response to stressful stimuli. HSPs have been shown repeatedly to confer protection in heat stroke and injury models. Interactions between HSPs and cytokines have received considerable attention in the literature within the last decade such that a complex pathway of interactions between cytokines, HSPs, and endotoxin is thought to be occurring in vivo in the orchestration of the APR to heat injury. These data suggest that much of the pathophysiologic changes observed with heat stroke are not a consequence of heat exposure, per se, but are representative of interactions among these three (and presumably additional) components of the innate immune response. This chapter will provide an overview of current knowledge regarding cytokine, HSP, and endotoxin interactions in heat stroke pathophysiology. Insight is provided into the potential therapeutic benefit of cytokine neutralization for mitigation of heat stroke morbidity and mortality based on our current understanding of their role in this syndrome.

Estimating the potential for twenty-first century sudden climate change

I investigate the potential for sudden climate change during the current century. This investigation takes into account evidence from the Earth's history, from climate models and our understanding of the physical processes governing climate shifts. Sudden alterations to climate forcing seem to be improbable, with sudden changes instead most likely to arise from climate feedbacks. Based on projections from models validated against historical events, dramatic changes in ocean circulation appear unlikely. Ecosystem-climate feedbacks clearly have the potential to induce sudden change, but are relatively poorly understood at present. More probable sudden changes are large increases in the frequency of summer heatwaves and changes resulting from feedbacks involving hydrology. These include ice sheet decay, which may be set in motion this century. The most devastating consequences are likely to occur further in the future, however. Reductions in subtropical precipitation are likely to be the most severe hydrologic effects this century, with rapid changes due to the feedbacks of relatively well-understood large-scale circulation patterns. Water stress may become particularly acute in the Southwest US and Mexico, and in the Mediterranean and Middle East, where rainfall decreases of 10-25% (regionally) and up to 40% (locally) are projected.

Action on climate change: the health risks of procrastinating

OBJECTIVE

The world's climate will continue to change because of human influence. This is expected to affect health, mostly adversely. We need to compare the projected health effects in Australia arising from differing climate change scenarios to inform greenhouse gas emission (mitigation) policy.

METHODS

We estimated health effects in Australia (heatwave mortality, dengue transmission regions) around 2100 under various greenhouse gas scenarios: "strong policy action" (efforts made now to reduce emissions) and "no policy action" (emissions continue at present high levels with no climate change-specific policies).

RESULTS

Compared with no policy action, mitigation could reduce the number of deaths caused by hot temperatures among older Australians by 4,000-7,000 a year (range reflects likely population size at 2100). Under a scenario of "no action", the zone of potential transmission of dengue fever expands 1,800 kilometres (km) south, as far as Sydney. In contrast, by markedly constraining greenhouse gas emissions now, this southward extension could be limited to 600 km (to Rockhampton). The number of displaced people within the Asia-Pacific region could increase (by orders of magnitude) under the "no action" scenario because of adverse socioecological circumstances aggravated by climate change.

CONCLUSIONS

Additional health effects will accrue as a result of the projected climate change throughout this century, and individuals and health systems should be prepared for some level of adaptation. However, timely and strong policy action to reduce greenhouse gas emissions would diminish the extent and severity of estimated future health effects.

Ecology: the proximate cause of frog declines?

Pounds et al. argue that global warming contributes to amphibian declines by encouraging outbreaks of the chytrid fungus Batrachochytrium dendrobatidis. Although our findings agree with the climate-linked epidemic hypothesis, this pathogen is probably not the only proximate factor in such cases: in the Trasimeno Lake area of Umbria in central Italy, for example, the water frog Rana lessonae first declined in the late 1990s, yet chytridiomycosis was not observed until 2003 (refs 5, 6). Here we show that the chytrid was common there throughout 1999-2002, in a previously unknown form that did not cause disease. We therefore think that the focus by Pounds et al. on a single pathogen is hard to justify because the host-parasite ecology is at present so poorly understood.

Urban environmental health hazards and health equity

This paper outlines briefly how the living environment can affect health. It explains the links between social and environmental determinants of health in urban settings. Interventions to improve health equity through the environment include actions and policies that deal with proximal risk factors in deprived urban areas, such as safe drinking water supply, reduced air pollution from household cooking and heating as well as from vehicles and industry, reduced traffic injury hazards and noise, improved working environment, and reduced heat stress because of global climate change. The urban environment involves health hazards with an inequitable distribution of exposures and vulnerabilities, but it also involves opportunities for implementing interventions for health equity. The high population density in many poor urban areas means that interventions at a small scale level can assist many people, and existing infrastructure can sometimes be upgraded to meet health demands. Interventions at higher policy levels that will create more sustainable and equitable living conditions and environments include improved city planning and policies that take health aspects into account in every sector. Health equity also implies policies and actions that improve the global living environment, for instance, limiting greenhouse gas emissions. In a global equity perspective, improving the living environment and health of the poor in developing country cities requires actions to be taken in the most affluent urban areas of the world. This includes making financial and technical resources available from high-income countries to be applied in low-income countries for urgent interventions for health equity. This is an abbreviated version of a paper on "Improving the living environment" prepared for the World Health Organization Commission on Social Determinants of Health, Knowledge Network on Urban Settings.

Climate change and developing-country cities: implications for environmental health and equity

Climate change is an emerging threat to global public health. It is also highly inequitable, as the greatest risks are to the poorest populations, who have contributed least to greenhouse gas (GHG) emissions. The rapid economic development and the concurrent urbanization of poorer countries mean that developing-country cities will be both vulnerable to health hazards from climate change and, simultaneously, an increasing contributor to the problem. We review the specific health vulnerabilities of urban populations in developing countries and highlight the range of large direct health effects of energy policies that are concentrated in urban areas. Common vulnerability factors include coastal location, exposure to the urban heat-island effect, high levels of outdoor and indoor air pollution, high population density, and poor sanitation. There are clear opportunities for simultaneously improving health and cutting GHG emissions most obviously through policies related to transport systems, urban planning, building regulations and household energy supply. These influence some of the largest current global health burdens, including approximately 800,000 annual deaths from ambient urban air pollution, 1.2 million from road-traffic accidents, 1.9 million from physical inactivity, and 1.5 million per year from indoor air pollution. GHG emissions and health protection in developing-country cities are likely to become increasingly prominent in policy development. There is a need for a more active input from the health sector to ensure that development and health policies contribute to a preventive approach to local and global environmental sustainability, urban population health, and health equity.

Model-based assessment of the role of human-induced climate change in the 2005 Caribbean coral bleaching event

Episodes of mass coral bleaching around the world in recent decades have been attributed to periods of anomalously warm ocean temperatures. In 2005, the sea surface temperature (SST) anomaly in the tropical North Atlantic that may have contributed to the strong hurricane season caused widespread coral bleaching in the Eastern Caribbean. Here, we use two global climate models to evaluate the contribution of natural climate variability and anthropogenic forcing to the thermal stress that caused the 2005 coral bleaching event. Historical temperature data and simulations for the 1870-2000 period show that the observed warming in the region is unlikely to be due to unforced climate variability alone. Simulation of background climate variability suggests that anthropogenic warming may have increased the probability of occurrence of significant thermal stress events for corals in this region by an order of magnitude. Under scenarios of future greenhouse gas emissions, mass coral bleaching in the Eastern Caribbean may become a biannual event in 20-30 years. However, if corals and their symbionts can adapt by 1-1.5 degrees C, such mass bleaching events may not begin to recur at potentially harmful intervals until the latter half of the century. The delay could enable more time to alter the path of greenhouse gas emissions, although long-term "committed warming" even after stabilization of atmospheric CO(2) levels may still represent an additional long-term threat to corals.

Impacts of global changes and extreme hydroclimatic events on macroinvertebrate community structures in the French Rhône River

We assessed the temporal changes in and the relationships between the structures of the macroinvertebrate communities and the environmental conditions of the French Rhône River (the river from Lake Geneva to the Mediterranean Sea) over the last 20 years (1985-2004). Multisite environmental and biological datasets were analysed using multiple CO-inertia analysis (MCOA) and Procrustean analysis. Changes in environmental conditions were mainly marked by an improvement in water quality between 1985 and 1991 and by an increase in water temperature from 1985 onwards due to climate change. Improvement in water quality seemed to delay changes in community structures under global warming. We then observed trends in community structures coupled with high temperatures and a decrease in oxygen content. Interestingly, we observed both gradual changes and rapid switches in community states. These shifts seemed coupled to extreme hydroclimatic events (i.e. pulse disturbances). Floods and the 2003 heatwave enhanced the development of eurytolerant and invasive taxa which were probably able to take advantage of gradual warming environmental conditions. Despite various site-specific "press" constraints (e.g. hydropower schemes, nuclear power plants), similar changes in community structures were observed along the French Rhône River. Such consistency in temporal processes at large geographical scales underlined the strength of hydroclimatic constraints on community dynamics compared to specific local disturbances. Finally, community structures did not show any sign of recovery, and their relative sensitivities to extreme hydroclimatic events seemed to increase with time. Thus, our results suggest that global changes may reduce the resilience of current community states.

Plasticity of photoprotective mechanisms of Buxus sempervirens L. leaves in response to extreme temperatures

Summer 2003 was unusually hot in Western Europe, with local droughts and an intense heatwave, that led to a massive damage in vegetation. Since high temperatures are supposed to generate photooxidative stress, we analysed photoprotective responses in leaves of the evergreen boxtree (Buxus sempervirens L.) during summer 2003. All the photoprotective compounds analysed (alpha-tocopherol, beta-carotene, and xanthophylls cycle pigments) were simultaneously induced in parallel with a reduction in photochemical efficiency (Fv/Fm). To characterise these responses, we compared these data with other data obtained during cold stress periods (2003, 2005) and with an unstressful summer (2002). Photoprotective responses observed during the heatwave were also induced by low temperature stress, and in both situations, this effect was exacerbated by light. In parallel with such induction the accumulation of red retro-carotenoids and xanthophyll esters was also observed under unfavourable conditions, suggesting a photoprotective role for both groups of carotenoids. This is the first report showing that in any species (Buxus sempervirens L.), the same retro-carotenoids can be induced in response to winter and summer stress. Present results demonstrate that the same mechanisms are induced as response to sub- and supraoptimal temperatures and the plasticity of such responses plays a critical role in plant acclimation to extreme temperatures, an ability that is specially important in the context of any future climate warming.

Blood-cerebrospinal fluid barrier in hyperthermia

The blood-CSF barrier (BCSFB) in choroid plexus works with the blood-brain barrier (BBB) in cerebral capillaries to stabilize the fluid environment of neurons. Dysfunction of either transport interface, i.e., BCSFB or BBB, causes augmented fluxes of ions, water and proteins into the CNS. These barrier disruptions lead to problems with edema and other compromised homeostatic mechanisms. Hyperthermic effects on BCSFB permeability and transport are not as well known as for BBB. However, it is becoming increasingly appreciated that elevated prostaglandin synthesis from fever/heat activation of cyclooxygenases (COXs) in the BCSFB promotes water and ion transfer from plasma to the ventricles; this harmful fluid movement into the CSF-brain interior can be attenuated by agents that inhibit the COXs. Moreover, new functional data from our laboratory animal model indicate that the BCSFB (choroidal epithelium) and the CSF-bordering ependymal cells are vulnerable to whole body hyperthermia (WBH). This is evidenced from the fact that rats subjected to 4h of heat stress (38 degrees C) showed a significant increase in the translocation of Evans blue and (131)Iodine from plasma to cisternal CSF, and manifested blue staining of the dorsal surface of the hippocampus and caudate nucleus. Degeneration of choroidal epithelial cells and underlying ependyma, a dilated ventricular space and damage to the underlying neuropil were frequent. A disrupted BCSFB is associated with a marked increase in edema formation in the hippocampus, caudate nucleus, thalamus and hypothalamus. Taken together, these findings suggest that the breaching of the BCSFB in hyperthermia significantly contributes to cell and tissue injuries in the CNS.

Comparative risk assessment of the burden of disease from climate change

The World Health Organization has developed standardized comparative risk assessment methods for estimating aggregate disease burdens attributable to different risk factors. These have been applied to existing and new models for a range of climate-sensitive diseases in order to estimate the effect of global climate change on current disease burdens and likely proportional changes in the future. The comparative risk assessment approach has been used to assess the health consequences of climate change worldwide, to inform decisions on mitigating greenhouse gas emissions, and in a regional assessment of the Oceania region in the Pacific Ocean to provide more location-specific information relevant to local mitigation and adaptation decisions. The approach places climate change within the same criteria for epidemiologic assessment as other health risks and accounts for the size of the burden of climate-sensitive diseases rather than just proportional change, which highlights the importance of small proportional changes in diseases such as diarrhea and malnutrition that cause a large burden. These exercises help clarify important knowledge gaps such as a relatively poor understanding of the role of nonclimatic factors (socioeconomic and other) that may modify future climatic influences and a lack of empiric evidence and methods for quantifying more complex climate-health relationships, which consequently are often excluded from consideration. These exercises highlight the need for risk assessment frameworks that make the best use of traditional epidemiologic methods and that also fully consider the specific characteristics of climate change. These include the longterm and uncertain nature of the exposure and the effects on multiple physical and biotic systems that have the potential for diverse and widespread effects, including high-impact events.

Impact of climate change on health: what is required of climate modellers?

The potential impacts of climate change on human health are significant, ranging from direct effects such as heat stress and flooding, to indirect influences including changes in disease transmission and malnutrition in response to increased competition for crop and water resources. Development agencies and policy makers tasked with implementing adaptive strategies recognize the need to plan for these impacts. However at present there is little guidance on how to prioritize their funding to best improve the resilience of vulnerable communities. Here we address this issue by arguing that closer collaboration between the climate modelling and health communities is required to provide the focused information necessary to best inform policy makers. The immediate requirement is to create multidisciplinary research teams bringing together skills in both climate and health modelling. This will enable considerable information exchange, and closer collaboration will highlight current uncertainties and hopefully routes to their reduction. We recognize that climate is only one aspect influencing the highly complex behaviour of health and disease issues. However we are optimistic that climate-health model simulations, including uncertainty bounds, will provide much needed estimates of the likely impacts of climate change on human health.

Control of microbial communities by the macrofauna: a sensitive interaction in the context of extreme summer temperatures?

Climate models predict an increasing frequency of extremely hot summer events in the northern hemisphere for the near future. We hypothesised that microbial grazing by the metazoan macrofauna is an interaction that becomes unbalanced at high temperatures due to the different development of the grazing rates of the metazoans and the growth rates of the microbial community with increasing temperature. In order to test this hypothesis, we performed grazing experiments in which we measured the impact of increasing temperatures on the development of the grazing rates of riverine mussels in relation to the growth rates of a unicellular prey community (a natural heterotrophic flagellate community from a large river). In a first experimental series using Corbicula fluminea as a grazer and under the addition of a carbon source (yeast extract), the increase of the prey's growth rates was considerably stronger than that of the predator's grazing rates when temperatures were increased from 19 to over 25 degrees C. This was also the outcome when the mussels had been acclimatized to warm temperatures. Hereafter, specific experiments with natural river water at temperatures of 25 and 30 degrees C were performed. Again, a strong decrease of the mussels' grazing rates in relation to the flagellate growth rates with increasing temperature occurred for two mussel species (C. fluminea and Dreissena polymorpha). When performing the same experiment using a benthic microbial predator community (biofilms dominated by ciliates) instead of the benthic mussels, an increase of the grazing rates relative to the growth rates with temperature could be observed. Our data suggest that predator-prey interactions (between metazoans and microbes) that are balanced at moderate temperatures could become unbalanced at high temperatures. This could have significant effects on the structure and function of microbial communities in light of the predicted increasing frequency of summer heat waves.

Land–atmosphere coupling and climate change in Europe

Increasing greenhouse gas concentrations are expected to enhance the interannual variability of summer climate in Europe and other mid-latitude regions, potentially causing more frequent heatwaves. Climate models consistently predict an increase in the variability of summer temperatures in these areas, but the underlying mechanisms responsible for this increase remain uncertain. Here we explore these mechanisms using regional simulations of recent and future climatic conditions with and without land-atmosphere interactions. Our results indicate that the increase in summer temperature variability predicted in central and eastern Europe is mainly due to feedbacks between the land surface and the atmosphere. Furthermore, they suggest that land-atmosphere interactions increase climate variability in this region because climatic regimes in Europe shift northwards in response to increasing greenhouse gas concentrations, creating a new transitional climate zone with strong land-atmosphere coupling in central and eastern Europe. These findings emphasize the importance of soil-moisture-temperature feedbacks (in addition to soil-moisture-precipitation feedbacks) in influencing summer climate variability and the potential migration of climate zones with strong land-atmosphere coupling as a consequence of global warming. This highlights the crucial role of land-atmosphere interactions in future climate change.

Extreme events due to human-induced climate change

A recent assessment by the intergovernmental panel on climate change concluded that the Earth's climate would be 2-6 degrees C warmer than in the pre-industrial era by the end of the twenty-first century, due to human-induced increases in greenhouse gases. In the absence of other changes, this would lead to the warmest period on Earth for at least the last 1000 years, and probably the last 100,000 years. The large-scale warming is expected to be accompanied by increased frequency and/or intensity of extreme events, such as heatwaves, heavy rainfall, storms and coastal flooding. There are also several possibilities that this large change could initiate nonlinear climate responses which lead to even more extreme and rapid (on the time-scale of decades) climate change, including the collapse of the ocean 'conveyor belt' circulation, the collapse of major ice sheets or the release of large amounts of methane in high latitudes leading to further global warming. Although these catastrophic events are much more speculative than the direct warming due to increased greenhouse gases, their potential impacts are great and therefore should be included in any risk assessment of the impacts of anthropogenic climate change.

Climate change and human health: impacts, vulnerability, and mitigation

It is now widely accepted that climate change is occurring as a result of the accumulation of greenhouse gases in the atmosphere arising from the combustion of fossil fuels. Climate change may affect health through a range of pathways--eg, as a result of increased frequency and intensity of heat waves, reduction in cold-related deaths, increased floods and droughts, changes in the distribution of vector-borne diseases, and effects on the risk of disasters and malnutrition. The overall balance of effects on health is likely to be negative and populations in low-income countries are likely to be particularly vulnerable to the adverse effects. The experience of the 2003 heat wave in Europe shows that high-income countries might also be adversely affected. Adaptation to climate change requires public-health strategies and improved surveillance. Mitigation of climate change by reducing the use of fossil fuels and increasing the use of a number of renewable energy technologies should improve health in the near term by reducing exposure to air pollution.

Whole-body hyperthermia in the rat disrupts the blood-cerebrospinal fluid barrier and induces brain edema

The present investigation was undertaken to find out whether whole-body hyperthermia (WBH) alters blood-cerebrospinal fluid barrier (BCSFB) permeability to exogenously-administered tracers and whether choroid plexus and ependymal cells exhibit morphological alterations in hyperthermia. Rats subjected to 4 hours of heat stress at 38 degrees C in a biological oxygen demand (BOD) incubator exhibited a profound increase in the BCSFB to Evans blue and radioiodine. Blue staining of the dorsal surface of the hippocampus and caudate nucleus and a significant increase in Evans blue and [131]Iodine in cisternal cerebrospinal fluid were seen following 4-hour heat stress compared to control. Degeneration of choroidal epithelial cells and underlying ependyma, a dilated ventricular space, and degenerative changes in the underlying neuropil were frequent. Hippocampus, caudate nucleus, thalamus, and hypothalamus exhibited profound increases in water content after 4 hours of heat stress. These observations suggest that hyperthermia induced by WBH is capable of breaking down the BCSFB and contributing to cell and tissue injury in the central nervous system.

Heatwaves and public health in Europe

Public health measures need to be implemented to prevent heat-related illness and mortality in the community and in institutions that care for elderly or vulnerable people. Heat health warning systems (HHWS) link public health actions to meteorological forecasts of dangerous weather. Such systems are being implemented in Europe in the absence of strong evidence of the effectiveness of specific measures in reducing heatwave mortality or morbidity. Passive dissemination of heat avoidance advice is likely to be ineffective given the current knowledge of high-risk groups. HHWS should be linked to the active identification and care of high-risk individuals. The systems require clear lines of responsibility for the multiple agencies involved (including the weather service, and the local health and social care agencies). Other health interventions are necessary in relation to improved housing, and the care of the elderly at home and vulnerable people in institutions. European countries need to learn from each other how to prepare for and effectively cope with heatwaves in the future. Including evaluation criteria in the design of heatwave early warning systems will help ensure effective and efficient system operation.

Climate change and human health: impacts, vulnerability and public health

It is now widely accepted that climate change is occurring as a result of the accumulation of greenhouse gases in the atmosphere arising from the combustion of fossil fuels. Climate change may affect health through a range of pathways, for example as a result of increased frequency and intensity of heat waves, reduction in cold related deaths, increased floods and droughts, changes in the distribution of vector-borne diseases and effects on the risk of disasters and malnutrition. The overall balance of effects on health is likely to be negative and populations in low-income countries are likely to be particularly vulnerable to the adverse effects. The experience of the 2003 heat wave in Europe shows that high-income countries may also be adversely affected. Adaptation to climate change requires public health strategies and improved surveillance. Mitigation of climate change by reducing the use of fossil fuels and increasing a number of uses of the renewable energy technologies should improve health in the near-term by reducing exposure to air pollution.

Climate change and human health: present and future risks

There is near unanimous scientific consensus that greenhouse gas emissions generated by human activity will change Earth's climate. The recent (globally averaged) warming by 0.5 degrees C is partly attributable to such anthropogenic emissions. Climate change will affect human health in many ways-mostly adversely. Here, we summarise the epidemiological evidence of how climate variations and trends affect various health outcomes. We assess the little evidence there is that recent global warming has already affected some health outcomes. We review the published estimates of future health effects of climate change over coming decades. Research so far has mostly focused on thermal stress, extreme weather events, and infectious diseases, with some attention to estimates of future regional food yields and hunger prevalence. An emerging broader approach addresses a wider spectrum of health risks due to the social, demographic, and economic disruptions of climate change. Evidence and anticipation of adverse health effects will strengthen the case for pre-emptive policies, and will also guide priorities for planned adaptive strategies.

The impacts of climate change on the risk of natural disasters

Human emissions of greenhouse gases are already changing our climate. This paper provides an overview of the relation between climate change and weather extremes, and examines three specific cases where recent acute events have stimulated debate on the potential role of climate change: the European heatwave of 2003; the risk of inland flooding, such as recently in Central Europe and Great Britain; and the harsh Atlantic hurricane seasons of 2004 and 2005. Furthermore, it briefly assesses the relation between climate change and El Niño, and the potential of abrupt climate change. Several trends in weather extremes are sufficiently clear to inform risk reduction efforts. In many instances, however, the potential increases in extreme events due to climate change come on top of alarming rises in vulnerability. Hence, the additional risks due to climate change should not be analysed or treated in isolation, but instead integrated into broader efforts to reduce the risk of natural disasters.

Disaster risk, climate change and international development: scope for, and challenges to, integration

Reducing losses to weather-related disasters, meeting the Millennium Development Goals and wider human development objectives, and implementing a successful response to climate change are aims that can only be accomplished if they are undertaken in an integrated manner. Currently, policy responses to address each of these independently may be redundant or, at worst, conflicting. We believe that this conflict can be attributed primarily to a lack of interaction and institutional overlap among the three communities of practice. Differences in language, method and political relevance may also contribute to the intellectual divide. Thus, this paper seeks to review the theoretical and policy linkages among disaster risk reduction, climate change and development. It finds that not only does action within one realm affect capacity for action in the others, but also that there is much that can be learnt and shared between realms in order to ensure a move towards a path of integrated and more sustainable development.

Impact of regional climate change on human health

The World Health Organisation estimates that the warming and precipitation trends due to anthropogenic climate change of the past 30 years already claim over 150,000 lives annually. Many prevalent human diseases are linked to climate fluctuations, from cardiovascular mortality and respiratory illnesses due to heatwaves, to altered transmission of infectious diseases and malnutrition from crop failures. Uncertainty remains in attributing the expansion or resurgence of diseases to climate change, owing to lack of long-term, high-quality data sets as well as the large influence of socio-economic factors and changes in immunity and drug resistance. Here we review the growing evidence that climate-health relationships pose increasing health risks under future projections of climate change and that the warming trend over recent decades has already contributed to increased morbidity and mortality in many regions of the world. Potentially vulnerable regions include the temperate latitudes, which are projected to warm disproportionately, the regions around the Pacific and Indian oceans that are currently subjected to large rainfall variability due to the El Niño/Southern Oscillation sub-Saharan Africa and sprawling cities where the urban heat island effect could intensify extreme climatic events.