Enhanced or Impaired?
II. Temperature-Induced Mortality
Which is more deadly … heat or cold? … rising temperatures or falling temperatures? The world's climate alarmists say it is warming that is to be avoided at all costs. Real-world data, however, suggest otherwise.
The positive health effects of heat have been well-documented over the past quarter-century. The early studies of Bull (1973) and Bull and Morton (1975a,b) in England and Wales, for example, demonstrated that even normal changes in temperature are typically associated with inverse changes in death rates, especially in older subjects. That is, when temperatures rise, death rates fall, while when temperatures fall, death rates rise. Also, Bull and Morton (1978) report "there is a close association between temperature and death rates from most diseases at all temperatures," and they say it is "very likely that changes in external temperature cause changes in death rates."
Another interesting finding of the study of Bull and Morton (1978) relates to extremes of heat and cold. They report that at the lower end of the temperature range, "there are more deaths the longer the 'run of days,' while at the higher end of the temperature range the reverse is true," i.e., "the longer the 'run' the fewer the deaths," suggesting that people adapt more readily to extreme heat than extreme cold. Among the various diseases that exhibit these relationships, they make particular note of "atherosclerotic diseases (strokes, ischemic heart disease, hypertension and diabetes)" and "respiratory diseases," which we will consider in more depth in that order.
A. Cardiovascular Diseases
A good place to begin a review of temperature-related mortality is a cold location … like Siberia. Hence, we start with the study of Feigin et al. (2000), who examined the relationship between stroke occurrence and weather parameters in the Russian city of Novosibirsk, which has one of the highest incidence rates of stroke in the entire world.
Analyzing the health records of 2208 patients with a sex and age distribution similar to that of the whole of Russia over the period 1982-93, Feigin et al. found a statistically significant association between stroke occurrence and low ambient temperature. For ischemic stroke (IS), which accounted for 87% of all strokes recorded, they report that the risk of IS occurrence on days with low ambient temperature is 32% higher than that on days with high ambient temperature. Hence, they suggested the implementation of "preventive measures … such as avoiding low temperature."
Hong et al. (2003) observed much the same thing in Incheon, Korea, over the period January 1998 to December 2000, reporting that "decreased ambient temperature was associated with risk of acute ischemic stroke," with the strongest effect being seen on the day after exposure to cold weather, further noting that "even a moderate decrease in temperature can increase the risk of ischemic stroke." In addition, they note that "risk estimates associated with decreased temperature were greater in winter than in the summer," which suggests, in their words, that "low temperatures as well as temperature changes are associated with the onset of ischemic stroke."
Nafstad et al. (2001) studied another cold place: Oslo, Norway. Thanks to Norwegian law, which requires all deaths to be examined by a physician who diagnoses cause and reports it on the death certificate, they were able to examine the effects of temperature on mortality due to all forms of cardiovascular disease for citizens of the country's capital over the period 1990 to 1995. Their analysis showed that the average daily number of cardiovascular-related deaths was 15% higher in the winter months (October-March) than in the summer months (April-September), leading them to also conclude that "a milder climate would lead to a substantial reduction in average daily number of deaths."
To see if these relationships between cold temperatures and cardiovascular mortality are preceded by an even more general health-temperature relationship, Hajat and Haines (2002) set out to determine if mere cardiovascular-related doctor visits by the elderly bore a similar relationship to cold temperatures. Based on data obtained for registered patients aged 65 and older from several London, England practices between January 1992 and September 1995, they did indeed find that the mean number of general practitioner consultations was higher in the cool-season months (October-March) than in the warm-season months (April-September) for all cardiovascular diseases.
Of course, one might say, such findings are only to be expected in cold climates. What about warm climates, where summer maximum temperatures are often extreme, but summer minimum temperatures are typically mild?
In Israel, research conducted by Green et al. (1994) revealed that between 1976 and 1985, mortality from cardiovascular disease was higher by 50% in mid-winter than in mid-summer, both in men and women and in different age groups, in spite of the fact that summer temperatures in the Negev, where much of the work was conducted, often exceed 30°C, while winter temperatures typically do not drop below 10°C. These findings are also substantiated by other Israeli studies that have been reviewed by Behar (2000), who states that "most of the recent papers on this topic have concluded that a peak of sudden cardiac death, acute myocardial infarction and other cardiovascular conditions is usually observed in low temperature weather during winter."
Evidence of a seasonal variation in cardiac-related mortality has additionally been noted in the relatively mild climate of southern California in the United States. In a study of all 222,265 death certificates issued by Los Angeles County for deaths caused by coronary artery disease from 1985 through 1996, Kloner et al. (1999) found that death rates in December and January were 33% higher than those observed in the period June through September. Likewise, based on a study of the Hunter region of New South Wales, Australia, that covered the period 1 July 1985 to 30 June 1990, Enquselassie et al. (1993) determined that "fatal coronary events and non-fatal definite myocardial infarction were 20-40% more common in winter and spring than at other times of year," while with respect to daily temperature effects, they found that "rate ratios for deaths were significantly higher for low temperatures," noting that "on cold days coronary deaths were up to 40% more likely to occur than at moderate temperatures."
In a study of both "hot" and "cold" cities in the United States -- where Atlanta, Georgia; Birmingham, Alabama; and Houston, Texas comprised the "hot" group, and where Canton, Ohio; Chicago, Illinois; Colorado Springs, Colorado; Detroit, Michigan; Minneapolis-St. Paul, Minnesota; New Haven, Connecticut; Pittsburgh, Pennsylvania; and Seattle and Spokane, Washington comprised the "cold" group -- Braga et al. (2002) determined both the acute effects and lagged influence of temperature on cardiovascular-related deaths. Their research revealed that in the hot cities, neither hot nor cold temperatures had much impact on mortality related to cardiovascular disease (CVD). In the cold cities, on the other hand, they report that both high and low temperatures were associated with increased CVD deaths, with the effect of cold temperatures persisting for days but the effect of high temperatures restricted to the day of the death or the day before. Of particular interest was the finding that for all CVD deaths the hot-day effect was five times smaller than the cold-day effect. In addition, the hot-day effect included some "harvesting," where the authors observed a deficit of deaths a few days later, which they did not observe for the cold-day effect.
Finally, in a study conducted in Sao Paulo, Brazil, based on data collected over the period 1991-1994, Gouveia et al. (2003) determined that the number of cardiovascular-related deaths in adults (15-64 years of age) increased by 2.6% for each 1°C decrease in temperature below 20°C, while there was no evidence for any heat-induced deaths due to temperatures rising above 20°C. In the elderly (65 years of age and above), however, a 1°C warming above 20°C led to a 2% increase in deaths; but a 1°C cooling below 20°C led to a 6.3% increase in deaths, or more than three times as many cardiovascular-related deaths due to cooling than to warming in the elderly.
The results of these several studies clearly demonstrate that global warming is actually beneficial to humanity, in that it reduces the incidence of cardiovascular diseases related to low temperatures and wintry weather by a much greater degree than it increases the incidence of cardiovascular diseases associated with high temperatures and summer heat waves.
B. Respiratory Diseases
As with cardiovascular-related mortality, respiratory-related deaths are also more likely to be associated with cold conditions in cold countries. For example, in the Oslo study where Nafstad et al. (2001) found winter deaths due to cardiovascular problems to be 15% more numerous than similar summer deaths, they determined that deaths due to respiratory diseases were fully 47% more numerous in winter than in summer. Likewise, the London study of Hajat and Haines (2002) revealed that the number of doctor visits by the elderly was also higher in cool-season than warm-season months for all respiratory diseases. At mean temperatures below 5°C, in fact, the relationship between respiratory disease consultations and temperature was linear, and stronger at a time lag of 6 to 15 days, such that a 1°C decrease in mean temperature below 5°C was associated with a 10.5% increase in all respiratory disease consultations. In addition, Gouveia et al. (2003) found that death rates in Sao Paulo, Brazil, due to a 1°C cooling were twice as great as death rates due to a 1°C warming in adults, and 2.8 times greater in the elderly.
Respiratory-related deaths were also investigated in the United States hot- and cold-city study of Braga et al. (2002), who found that increased temperature variability was the most relevant aspect of climate change with respect to this category of disease in this part of the world. Why is this finding important? Because Robeson (2002) has clearly demonstrated, from a 50-year study of daily temperatures at more than 1,000 U.S. weather stations, that temperature variability declines with warming, and at a very substantial rate, so that reduced temperature variability in a warmer world would lead to reductions in temperature-related deaths at both the high and low ends of the daily temperature spectrum at all times of the year.
As is the case with human cardiovascular health, therefore, these several studies make it abundantly clear that a warming world should positively impact the respiratory health of the world's citizens.
C. Vector-Borne Diseases
In an article in Science entitled "The global spread of malaria in a future, warmer world," Rogers and Randolph (2000) note that "predictions of global climate change have stimulated forecasts that vector-borne diseases will spread into regions that are at present too cool for their persistence," which predictions comprise one of the major global-warming scare-stories of the world's climate alarmists. There are, however, several problems associated with this scenario.
According to Reiter (2000), claims that malaria resurgence is the product of CO2-induced global warming ignore other important factors and disregard known facts. An historical analysis of malaria trends, for example, reveals that this disease was an important cause of illness and death in England during a period of colder-than-present temperatures throughout what has come to be called the Little Ice Age. What is more, its transmission began to decline only in the 19th century, during a warming phase, when, according to Reiter, "temperatures were already much higher than in the Little Ice Age."
We could well ask ourselves, therefore, why malaria was so prevalent in Europe during some of the coldest centuries of the past millennium and why we have witnessed malaria's widespread decline at a time when temperatures have been warming. Clearly, there must be other factors at work that are more important than temperature to the spread of malaria. And there are! -- factors such as the quality of public health services, irrigation and agricultural activities, land use practices, civil strife, natural disasters, ecological change, population change, the use of insecticides and the movement of people, as well as other climatic factors (Reiter, 2000, 2001; Hay et al., 2002).
These same sentiments are expressed by Kuhn et al. (2003), who analyzed the determinants of temporal trends in malaria deaths within England and Wales from 1840-1910. With respect to temperature changes over the period of study, they report finding that "a 1°C increase or decrease was responsible for an increase in malaria deaths of 8.3% or a decrease of 6.5%, respectively," which they say explains "the malaria epidemics in the 'unusually hot summers' of 1848 and 1859." Nevertheless, there was a long-term near-linear temporal decline in malaria deaths over the period of study, which they say "was probably driven by nonclimatic factors." Foremost among the factors they list in this regard are increasing livestock populations (which tend to divert mosquito biting from humans), decreasing acreages of marsh wetlands (where mosquitoes breed), as well as "improved housing, better access to health care and medication, and improved nutrition, sanitation, and hygiene."
Kuhn et al. additionally note that the number of secondary malaria cases arising from each primary imported case "is currently minuscule," as demonstrated by the absence of any secondary malaria cases in the UK since 1953. Hence, they conclude that although the increase in temperature predicted for Britain by 2050 is likely to cause an 8-14% increase in the potential for malaria transmission, "the projected increase in proportional risk is clearly insufficient to lead to the reestablishment of endemicity." Expanding on this statement, they note that "the national health system ensures that imported malaria infections are detected and effectively treated and that gametocytes are cleared from the blood in less than a week." For Britain, therefore, they conclude that "a 15% rise in risk might have been important in the 19th century, but such a rise is now highly unlikely to lead to the reestablishment of indigenous malaria," since "socioeconomic and agricultural changes" have greatly altered the cause-and-effect relationships of the past.
Why, then, do climate alarmists predict widespread increases in malaria in response to global warming? They do it because nearly all of the studies they cite ignore these non-climatic factors and additionally use only one, or at most two, climate variables to characterize the current distribution of the disease when developing models to predict its future distribution. In contrast, Rogers and Randolph (2000) developed a predictive model that employs a total of five climate variables and obtained very different results: a mere 0.84% increase in potential malaria exposure under what they call the "medium-high" scenario of global warming and a 0.92% decrease under the "high" scenario. They thus rightly note that their model "contradicts prevailing forecasts of global malaria expansion" and that "it highlights the use [we would say superiority] of multivariate rather than univariate constraints in such applications."
Using a similar approach, Hay et al. (2002) investigated long-term trends in meteorological data at four East African highland sites that experienced significant increases in malaria cases over the past couple of decades, reporting that "temperature, rainfall, vapour pressure and the number of months suitable for P. falciparum transmission have not changed significantly during the past century or during the period of reported malaria resurgence." Hence, these factors could not be responsible for the observed increases in malaria cases recently noted at these sites. Likewise, Shanks et al. (2000) examined trends in temperature, precipitation and malaria rates in western Kenya over the period 1965-1997, also finding absolutely no linkages among the variables.
It would thus appear that models used by climate alarmists to predict the spread of malaria in response to global warming are much too simplistic to reveal its true climatic dependency. In addition, the possibility that malaria expansion might occur as a result of rising temperatures is further severely weakened by the potential for effective human intervention. In the words of Dye and Reiter (2000), "given adequate funding, technology, and, above all, commitment, the campaign to 'Roll Back Malaria,' spearheaded by the World Health Organization, will have halved deaths related to [malaria] by 2010," so that "by 2050, the map of malaria distribution should bear little resemblance to the one drawn by Rogers and Randolph." In fact, if all goes well, there may not even be such a map!
Pretty much the same things can be said about dengue and yellow fever; and, in fact, they have been said. Reiter (2001), for example, notes that the natural history of these vector-borne diseases is highly complex; and the interplay of climate, ecology, vector biology and a number of other factors defies definition by the simplistic analyses utilized in the models employed by climate alarmists to generate predictions of future increases in the spread of these diseases under various global warming scenarios. There have been some reports of a recent resurgence of mosquito-born maladies in certain parts of the world; but, as Reiter states, it is "facile to attribute this resurgence to climate change." Indeed, he presents a case-by-case analysis demonstrating that factors associated with politics, economics and human activity -- but not climate change -- are the principal determinants of the spread of these diseases, going on to conclude that it is "inappropriate to use climate-based models to predict future prevalence."
There has also been some concern of late with respect to a potential cholera-climate connection. Pascual et al. (2002), for example, report that recent data analyses support a temporal association between the El Niño-Southern Oscillation (ENSO) phenomenon and the interannual variability of cholera in certain parts of the world, as well as a role of increased water temperature in enhancing the survival and growth of the pathogen that is responsible for the disease, although they say "it is not yet possible to assess the strength of particular climatic drivers." In addition, they report that variations in water volume "can have dramatic effects on disease dynamics, perhaps more pronounced than those of factors affecting the pathogen's growth and survival."
Although climatic factors undoubtedly are involved in the dynamics of cholera, they are not well defined; and even when they ultimately are understood, the importance of socio-economic factors for the development and spread of cholera -- which is often described, in the words of Pascual et al., as "the disease of poverty" -- will likely far outweigh them. As the researchers describe the situation, "the importance of sanitary conditions is clearly indisputable," in support of which declaration they cite the fact that "infrastructure providing safe water and sewage treatment in industrialized nations has made the sustained transmission of cholera extremely unlikely." Hence, it would appear that the best long-term preventive measures to take against cholera would be those that enhance the wealth of nations and their citizens.
Another major vector-borne disease is tick-borne encephalitis (TBE), which according to Randolph and Rogers (2000) "is the most significant vector-borne disease in Europe and Eurasia," having "a case morbidity rate of 10-30% and a case mortality rate of typically 1-2% but as high as 24% in the Far East." The flavivirus (TBEV) that causes TBE is maintained in natural rodent-tick cycles; and humans may be infected if bitten by an infected tick or by drinking untreated milk from infected sheep or goats.
Early writings on the relationship of this disease to global warming predicted that TBE -- like so many other vector-born diseases -- would expand its range and become more of a threat to humans in a warmer world. However, Randolph and Rogers draw our attention to the fact that "like many vector-borne pathogen cycles that depend on the interaction of so many biotic agents with each other and with their abiotic environment, enzootic cycles of TBEV have an inherent fragility," such that "their continuing survival or expansion cannot be predicted from simple univariate correlations." Hence, the two researchers decided to explore the subject in significantly greater detail than had ever been done before.
Confining their analysis to Europe, Randolph and Rogers first matched the present-day distribution of TBEV to the present-day distribution of five climatic variables: average monthly mean, maximum and minimum temperatures, plus rainfall and saturation vapor pressure, "to provide a multivariate description of present-day areas of disease risk." They then applied this understanding to outputs of a general circulation model of the atmosphere that predicted how these five climatic variables may change in the future.
The results of this effort indicated that the distribution of TBEV may expand both north and west of Stockholm, Sweden, in a warming world. Elsewhere, however, the authors say that "fears for increased extent of risk from TBEV caused by global climate change appear to be unfounded." In fact, they note that "the precise conditions required for enzootic cycles of TBEV are predicted to be disrupted" in response to global warming, while the new climatic state "appears to be lethal for TBEV."
This analysis, in Randolph and Rogers' words, "gives the lie to the common perception that a warmer world will necessarily be a world under greater threat from vector-borne diseases." In the case of TBEV, in fact, they note that the predicted change "appears to be to our advantage."
A similar conclusion was reached by Estrada-Peña (2003), who studied the effects of various abiotic factors on the habitat suitability of four tick species that are major vectors of livestock pathogens in South Africa. This work led to the development of species-specific models of tick habitat suitability, which indicated that "year-to-year variations in the forecasted habitat suitability over the period 1983-2000 show a clear decrease in habitat availability, which is attributed primarily to increasing temperature in the region over this period." In addition, when climate variables were projected to the year 2015, it was determined that "the simulations show a trend toward the destruction of the habitats of the four tick species."
Commenting on this finding, Estrada-Peña notes that "it is often suggested that one of the most important societal consequences of climate change may be an increase in the geographic distribution and transmission intensity of vector-borne disease." In the cases of the four disease-carrying ticks of South Africa described in this study, however, just the opposite was observed.
In considering the several findings described in this section, it is clear that vector-borne diseases are unlikely to be affected in any major way by a continuation of the most recent -- and possibly still on-going -- spate of global warming that has brought about the welcome demise of the Little Ice Age and ushered in the productive and prosperous Modern Warm Period.
D. All Diseases
In a study of mortality in general, Keatinge and Donaldson (2001) analyzed the effects of temperature, wind, rain, humidity and sunshine during high pollution days in the greater London area over the period 1976-1995 to determine what weather and/or pollution factors have the biggest influence on human mortality. Their most prominent finding was that simple plots of mortality rate versus daily air temperature revealed a linear increase in deaths as temperatures fell from 15°C to near 0°C. Mortality rates at temperatures above 15°C were, in the words of the researchers, "grossly alinear," showing no trend. Days with high pollutant concentrations were colder than average, but a multiple regression analysis revealed that no pollutant was associated with a significant increase in mortality among people over fifty years of age. Indeed, only low temperatures were shown to have a significant effect on both immediate (1 day after the temperature perturbation) and long-term (up to 24 days after the temperature perturbation) mortality rates.
In a closely allied study, Keatinge et al. (2000) examined heat- and cold-related mortality in north Finland, south Finland, southwest Germany, the Netherlands, Greater London, north Italy, and Athens, Greece, in people aged 65-74. For each of these regions, they determined the 3°C temperature interval of lowest mortality and then evaluated mortality deviations from that base level as temperatures rose and fell by 0.1°C increments. The result, according to the researchers, was that "all regions showed more annual cold related mortality than heat related mortality." In fact, over the seven regions studied, annual cold related deaths were nearly ten times greater than annual heat related deaths. The scientists also note that the very successful adjustment of the different populations they studied to widely different summer temperatures "gives grounds for confidence that they would adjust successfully, with little increase in heat related mortality, to the global warming of around 2°C predicted to occur in the next half century." Indeed, they say their data suggest that "any increases in mortality due to increased temperatures would be outweighed by much larger short term declines in cold related mortalities." For the population of Europe, therefore, an increase in temperature would appear to be a climate change for the better.
Gouveia et al. (2003) conducted a similar study in Sao Paulo, Brazil, where they tabulated the numbers of daily deaths from all causes (excepting violent deaths and deaths of infants up to one month of age), which they obtained from the city's mortality information system for the period 1991-1994. They then analyzed these data for children (less than 15 years of age), adults (ages 15-64), and the elderly (age 65 and above) with respect to the impacts of warming and cooling. For each 1°C increase above the minimum-death temperature of 20°C for a given and prior day's mean temperature, there was a 2.6% increase in deaths from all causes in children, a 1.5% increase in deaths from all causes in adults, and a 2.5% increase in deaths from all causes in the elderly. For each 1°C decrease below the 20°C minimum-death temperature, however, the cold effect was greater, with increases in deaths from all causes in children, adults and the elderly registering 4.0%, 2.6% and 5.5%, respectively, which cooling-induced death rates are 54%, 73% and 120% greater than those attributable to warming.
In a similar study conducted in Shanghai, China, from 1 Jun 2000 to 31 Dec 2001, Kan et al. (2003) found a V-like relationship between total mortality and temperature that had a minimum mortality risk at 26.7°C. Above this temperature, they note that "total mortality increased by 0.73% for each degree Celsius increase; while for temperatures below the optimum value, total mortality decreased by 1.21% for each degree Celsius increase." Hence, it can be appreciated that the net effect of a warming of the climate of Shanghai would likely be reduced mortality on the order of 0.5% per degree Celsius increase in temperature, or perhaps even more, in light of the fact that the warming of the past few decades has been primarily due to increases in daily minimum temperatures.
In the United States, Goklany and Straja (2000) studied deaths due to all causes over the period 1979-97, finding there were no trends due to either extreme heat or cold in the entire population or, even more remarkably, in the older more susceptible age groups, i.e., those aged 65 and over, 75 and over, and 85 and over. Nevertheless, deaths due to extreme cold exceeded those due to extreme heat by 80% to 125%. With respect to the absence of trends in U.S. death rates attributable to either extreme heat or cold, Goklany and Straja say this observation "suggests that adaptation and technological change may be just as important determinants of such trends as more obvious meteorological and demographic factors."
Donaldson et al. (2003) suggest much the same thing. For three areas of the world -- North Carolina, USA; South Finland; and Southeast England -- they determined the mean daily May-August 3°C temperature bands in which deaths of people aged 55 and above were at a minimum. Then they compared heat- and cold-related deaths that occurred at temperatures above and below this optimum temperature interval for each region, after which they determined how heat-related deaths in the three areas changed between 1971 and 1997 in response to: (1) the 1.0°C temperature rise that was experienced in North Carolina over this period (from an initial temperature of 23.5°C), (2) the 2.1°C temperature rise experienced in Southeast England (from an initial temperature of 14.9°C), and (3) the unchanging 13.5°C temperature of South Finland.
First, it was determined that the 3°C temperature band at which mortality was at its local minimum was lowest for the coolest region (South Finland), highest for the warmest region (North Carolina), and intermediate for the region of intermediate temperature (Southeast England). This finding suggests that the populations of the three regions were somewhat acclimated to their respective thermal regimes. Second, for each of the three regions, it was determined that cold-related mortality (expressed as excess mortality at temperatures below the region's optimum 3°C temperature band), was greater than heat-related mortality (expressed as excess mortality at temperatures above the region's optimum 3°C temperature band).
As for the third aspect of the study, i.e., changes in heat-related mortality from 1971 to 1997, it was determined that in the coldest of the three regions (South Finland, where there was no change in temperature over the study period), heat-related deaths per million inhabitants in the 55-and-above age group declined from 382 to 99. In somewhat warmer Southeast England, however, where it warmed by a whopping 2.1°C over the study period, heat-related deaths per million of the at-risk age cohort still declined, but this time from only 111 to 108. Last of all, in the warmest of the three regions (North Carolina, USA, where mean daily May-August temperature rose by 1.0°C over the study period), corresponding heat-related deaths also fell, and this time from 228 to a mere 16 per million.
From these several observations we learn that most people can adapt to both warmer and cooler climates and that cooling tends to produce many more deaths than warming, irrespective of the initial temperature regime. As for the reason behind the third observation -- the dramatic decline in heat-related deaths in response to warming in the hottest region of the study (North Carolina) -- Donaldson et al. (2003) attribute it to the increase in the availability of air conditioning in the South Atlantic region of the United States, where they note that the percentage of households with some form of air conditioning rose from 57% in 1978 to 72% in 1997. With respect to the declining heat-related deaths in the other two areas, they say "the explanation is likely to lie in the fact that both regions shared with North Carolina an increase in prosperity, which could be expected to increase opportunities for avoiding heat stress."
Another revealing investigation into the comparative dangers of unseasonably hot and cold temperatures was conducted by Huynen et al. (2001), who analyzed mortality rates in the entire population of Holland. For the 19-year period 1 January 1979 through 31 December 1997, the group of five scientists compared the numbers of deaths in people of all ages that occurred during well-defined heat waves and cold spells. Their bottom-line findings indicated there was a total excess mortality of 39.8 deaths per day during heat waves and 46.6 deaths per day during cold spells.
These numbers indicate that a typical cold-spell day kills at a rate that is 17% greater than a typical heat-wave day in the Netherlands. In addition, the researchers note that the heat waves they studied ranged from 6 to 13 days in length, while the cold spells lasted 9 to 17 days, making the average cold spell approximately 37% longer than the average heat wave. Adjusting for this duration differential thus makes the number of deaths per cold spell in the Netherlands fully 60% greater than the number of deaths per heat wave. What is more, excess mortality continued during the whole month after the cold spells, leading to even more deaths; while in the case of heat waves, there actually appeared to be mortality deficits in the following month, which suggests, in the words of the authors, "that some of the heat-induced increase in mortality can be attributed to those whose health was already compromised" or "who would have died in the short term anyway." This same conclusion has also been reached in a number of other studies (Kunst et al., 1993; Alberdi et al., 1998; Eng and Mercer, 1998; Rooney et al., 1998). It is highly likely, therefore, that the 60% greater death toll we have calculated for Dutch cold spells as compared to Dutch heat waves is a vast underestimate of the true differential killing power of these two extreme weather phenomena.
The Dutch could well ask themselves, therefore, "Will global climate change reduce thermal stress in the Netherlands?" ... which is exactly what the senior and second authors of the Huynen et al. paper did in a letter to the editor of Epidemiology that bore that very title (Martens and Huynen, 2001). Based on the predictions of nine different GCMs for an atmospheric CO2 concentration of 550 ppm in the year 2050 -- which implied a 50% increase in Dutch heat waves and a 67% drop in Dutch cold spells -- they calculated a total mortality decrease for Holland of approximately 1100 people per year at that point in time.
Yes, global warming -- if it continues, and for whatever reason -- will result, not in more lives lost, but in more lives saved. And it's not just the Dutch that will be thus blessed; data from all over the world tell the same story.
Take Germany, for instance. Laschewski and Jendritzky (2002) analyzed daily mortality rates of the population of Baden-Wurttemberg (10.5 million inhabitants) over the 30-year period 1958-1997 to determine the sensitivity of the people living in this moderate climatic zone of southwest Germany to long-and short-term episodes of heat and cold. With respect to long-term conditions, they note that the mortality data "show a marked seasonal pattern with a minimum in summer and a maximum in winter." With respect to short-term conditions, they report that "cold spells lead to excess mortality to a relatively small degree, which lasts for weeks," and that "the mortality increase during heat waves is more pronounced, but is followed by lower than average values in subsequent weeks." These scientists also say this latter observation suggests that people who died from short-term exposure to heat likely "would have died in the short term anyway."
With respect to this short-term mortality displacement in the case of heat-related deaths, we note that the authors' data demonstrate it is precisely that, i.e., merely a displacement of deaths and not an overall increase. They found, for example, that the mean duration of above-normal mortality for the 51 heat episodes that occurred from 1968 to 1997 was 10 days, with a mean increase in mortality of 3.9%, after which there was a mean decrease in mortality of 2.3% for 19 days. Hence, the net effect of the two perturbations was essentially nil (actually, a calculated overall decrease in mortality of 0.2% over the full 29-day period).
In light of the knowledge gained from these several studies of the effects of temperature on human mortality due to all health problems, it can readily be appreciated that it is cooling that kills, not warming. Hence, those people who claim to be concerned about the health effects of climate change are being dishonest with both themselves and others when they say that CO2-induced global warming is killing people. In point of fact, CO2-induced global warming -- if it is even occurring at all -- is enabling earth's populace to actually lead both longer and more productive lives.