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Health Effects (Temperature - Hot vs. Cold: Europe) -- Summary
What is global warming doing to our health?  In this Summary we look for answers provided by 21st-century studies conducted in Europe, where heads of state and their subordinate ministers keep telling us it is killing us.

We begin with the comprehensive work of Keatinge et al. (2000), who studied 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 3C temperature interval of lowest mortality and then evaluated mortality deviations from that base level as temperatures rose and fell by increments of 0.1C.  As they describe their findings, "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.  Moreover, Keatinge et al. note that the very successful adjustment of the different populations in their study 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 2C 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 entire population of Europe, therefore, even a 2C increase in temperature, if it were ever to occur, would appear to be a climate change for the better.

Building on the findings of this first study, 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 which weather and/or pollution factors have the biggest influence on human mortality.  They observed, first of all, that simple plots of mortality rate versus daily air temperature revealed a linear increase as temperatures fell from 15C to near 0C.  Mortality rates at temperatures above 15C, however, were "grossly alinear," as they describe it, showing no trend.  Days with high SO2, CO or PM10 (particulate matter of diameter less than 10m) concentrations were colder than average, but a multiple regression analysis revealed that none of these pollutants was associated with a significant increase in mortality among people 50 years of age or older.  Indeed, only low temperatures were found to have a significant effect on both immediate mortality (1 day after a temperature perturbation) and long-term mortality (up to 24 days after a temperature perturbation), with the net increase in mortality over the 24 days following a 1-day fall in temperature amounting to 2.77 daily deaths per million people per degree Celsius temperature drop.  In light of these several observations, Keatinge and Donaldson conclude that "the large, delayed increase in mortality after low temperature is specifically associated with cold and is not due to associated patterns of wind, rain, humidity, sunshine, SO2, CO, or smoke."

Simply put, Keatinge and Donaldson determined that cold kills.  So how does it do it?  Quoting the two scientists in another context, they say that "cold causes mortality mainly from arterial thrombosis and respiratory disease, attributable in turn to cold-induced hemoconcentration and hypertension [in the first case] and respiratory infections [in the second case]."  McGregor (2005) additionally notes that "anomalous cold stress can increase blood viscosity and blood pressure due to the activation of the sympathetic nervous system which accelerates the heart rate and increases vascular resistance (Collins et al., 1985; Jehn et al., 2002; Healy, 2003; Keatinge et al., 1984; Mercer, 2003; Woodhouse et al., 1993)," and that "anomalously cold winters may also increase other risk factors for heart disease such as blood clotting or fibrinogen concentration, red blood cell count per volume and plasma cholesterol."  Consequently, Keatinge and Donaldson conclude that although "increases in mortality due to cold weather are large in many temperate regions ... effective protection against personal cold exposure virtually prevents excess winter mortality," even in places as cold as Siberia; and we hardly need to repeat that global warming can be a part of that protection against personal cold exposure.

In a study that explicitly considered the question of personal cold exposure, Gemmell (2001) analyzed the answers of 858 respondents to pertinent health and housing questions put to them in the second sweep of the "West of Scotland Twenty-07 Study," which was conducted in 1991.  This effort indicated that "over and above socioeconomic factors and house conditions, inadequate home heating is associated with poor health in those aged 55-60."  Gemmel notes, for example, that "respondents who reported feeling cold in winter 'most of the time' were over three times more likely to suffer from a limiting condition and almost five times as likely to report 'fair' or 'poor' self assessed health," leading him to conclude that "living in a cold house will almost certainly exacerbate existing conditions and may lead to early mortality."

Based on these findings, Gemmell suggests that "affordable efficient methods of home heating could help reduce the number of people living in homes that are detrimental to their health."  So also would increasing minimum air temperatures help in this regard, which is something that global warming excels at doing.  It should also be noted in this regard that climate-alarmist attempts to make fossil fuels and the electricity they produce more costly would greatly aggravate this situation, particularly among those who can least afford to heat their homes, i.e., the world's poor.  Hence, it can be appreciated that Kyoto-type "solutions" to the global warming "problem" not only accomplish no good, they do just the opposite, harming those who can least help themselves, in a cruel irony of misguided logic.

Also working in the British Isles, England to be specific, Hajat and Haines (2002) set out to determine whether or not the well-documented relationship between cold temperatures and cardiovascular and respiratory mortality in the elderly extends to the number of visits by the elderly to general practitioners.  To accomplish this objective, they used general additive models to regress time-series of daily numbers of general practitioner consultations by the elderly against temperature, where consultations were only counted if they were for the purpose of discussing the following respiratory and cardiovascular complaints, as obtained for registered patients aged 65 and older from several London practices between January 1992 and September 1995: asthma, lower respiratory disease excluding asthma, upper respiratory disease excluding allergic rhinitis, and cardiovascular disease.  This work revealed that the number of consultations was higher in cool-season months (October-March) than in warm-season months (April-September) for all cardiovascular and respiratory diseases.  In addition, at temperatures below 5C, the relationship between respiratory disease consultations and temperature was linear, and stronger at a time lag of 6 to 15 days, such that a 1C decrease in mean temperature below 5C was associated with a 10.5% increase in all respiratory disease consultations.  The results of this study thus once again demonstrate the profound negative influence of cold temperatures on the health of the elderly.  Warmer is definitely better than colder; and compared to the Little Ice Age - out of which the planet gradually emerged over the past two centuries - the Modern Warm Period is a godsend.

But what about the extreme warmth of heat waves? Kovats et al. (2004) note that "under all realistic scenarios of future climate change, the frequency of heat waves in the UK is projected to increase significantly over coming decades, raising the question of how best to meet the public health threats that more frequent and prolonged periods of hot weather will present."  Hence, they studied patterns of temperature-related hospital admissions and deaths in Greater London during the mid 1990s to help shed some light on the subject.  Their research showed that for the 3-year period 1994-96, cardiovascular-related deaths were approximately 50% greater during the coldest part of the winter than during the peak warmth of summer, while respiratory-related deaths were nearly 150% greater in the depth of winter cold than at the height of summer warmth.  Also, with respect to the heat waves that climate alarmists portray as being such vicious killers, it is revealing to note that the mortality impact of the "deadly" heat wave of 29 July to 3 August 1995 (which Kovats et al. find to have boosted daily mortality by just over 10%) was so tiny that it could not even be discerned amongst the random data scatter of their plots of three-year-average daily deaths from cardiovascular and respiratory problems vs. day of year.

In a final study from England, McGregor (2005) conducted an analysis to determine if there was any association between the level of ischaemic heart disease (IHD) mortality in three English counties (Hampshire, West Midlands and West Yorkshire) and the winter-season North Atlantic Oscillation (NAO), which exerts a fundamental control on the nature of winter climate in Western Europe, focusing on the winters of 1974-75 through 1998-99.  In doing so, he discovered that "generally below average monthly and all winter IHD mortality is associated with strong positive values of the monthly or winter climate index which indicates the predominance of anomalously warm moist westerly flows of air over England associated with a positive phase of the NAO."  Likewise, at the other extreme, he found that "winters with elevated mortality levels ... have been shown to be clearly associated with a negative NAO phase and anomalously low temperatures."

The same types of results have been obtained nearly everywhere in Europe.  In Norway, for example, Nafstad et al. (2001) studied the association between temperature and daily mortality among citizens of Oslo over the period 1990-1995, categorizing and examining the effects of temperature on mortality arising from (1) respiratory diseases, (2) cardiovascular diseases, and (3) all diseases (excluding deaths caused by accidents, poisoning, suicide, or other non-normal factors).  They found that the average daily number of deaths in all three categories was higher in winter (October-March) than in summer (April-September).  For respiratory diseases, winter deaths were 47% more numerous than summer deaths; while for cardiovascular diseases and the all-disease category, winter deaths were 15% more numerous than summer deaths.  As a result of these findings, they concluded that "a milder climate would lead to a substantial reduction in average daily number of deaths," suggesting that a little global warming would be an effective means of extending the longevity of Norway's citizens.

In Spain, Diaz et al. (2005) examined the effect of extreme winter temperature on mortality in Madrid for people older than 65, using data from 1,815 winter days over the period 1986-1997, during which time a total of 133,000 deaths occurred.  One of their most important findings was that daily Tmax was more closely correlated with mortality than was daily Tmin, because, as they describe it, "very low Tmin occur mostly during stagnation episodes, characterized by very cold nights and sunny days, with a typical temperature range of between 15C and 20C," while "most of the days with very low Tmax occur under cloudy conditions, with very limited temperature ranges of around 5C," so that "human exposure to low temperatures during these days is longer than that occurring during the stagnation days associated with a very low Tmin."  In addition, they note that "Tmin is usually recorded around 7 a.m., when very little human activity occurs outdoors, while Tmax is usually recorded at around 4 p.m."

Diaz et al. additionally determined that as Tmax dropped below 6C, which they describe as an unusually cold day (UCD), "the impact on mortality also increased significantly."  What is more they found that the impact of UCDs increased as the winter progressed, with the first UCD of the season producing an average of 102 deaths/day at a lag of 8 days and the sixth UCD producing an average of 123 deaths/day at a lag of 8 days.  This behavior suggests, in their words, that "acclimatisation does not occur, with every cold spell enhancing the pathologies produced in previous spells."  Consequently, whereas they report that "the impact of heat waves is reduced as they occur during a certain season, suggesting an acclimatisation to heat," just the opposite occurs in the case of recurring cold, which becomes ever more deadly with each new occurrence.  In light of these observations it is clear that (1) cold kills, (2) extreme cold kills even better, and (3) recurring extreme cold kills best of all, even in a climate as moderate as that of Madrid.

In Germany, Laschewski and Jendritzky (2002) analyzed daily mortality rates in Baden-Wurttemberg (10.5 million inhabitants) over the 30-year period 1958-97 to determine the sensitivity of the population of this moderate climatic zone to long- and short-term episodes of heat and cold.  Their research indicated that mortality shows "a marked seasonal pattern with a minimum in summer and a maximum in winter."  With respect to short-term exposure to heat and cold, they found 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."  The authors say this latter observation suggests that people who died from short-term exposure to heat possibly "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 Laschewski and Jendritzky's 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 an overall decrease in mortality of 0.2% over the full 29-day period.  Consequently, it should be abundantly clear that cold spells are much more deadly than heat waves.  Hence, we could expect global warming to confer significant benefits upon mankind in both the short- and long-term; for in both situations, cold kills but heat heals, especially in the long-term, which is what global warming is all about.

In the Czech Republic, Kysely and Huth (2004) calculated deviations of the observed number of deaths from the expected number of deaths for each day of the year for the period 1992-2000.  This procedure revealed that "the distribution of days with the highest excess mortality in a year is clearly bimodal, showing a main peak in late winter and a secondary one in summer."  In the case of the smaller number of summer heat-wave-induced deaths, they also found that "a large portion of the mortality increase is associated with the harvesting effect, which consists in short-term shifts in mortality and leads to a decline in the number of deaths after hot periods (e.g. Rooney et al., 1998; Braga et al., 2002; Laschewski and Jendritzky, 2002)."  For the Czech Republic, they report that "the mortality displacement effect in the severe 1994 heat waves can be estimated to account for about 50% of the total number of victims."  As they describe it, "people who would have died in the short term even in the absence of oppressive weather conditions made up about half of the total number of deaths."  Hence, not only is the overall number of deaths typically smaller in the warmest part of the year than in the coldest part of the year in the Czech Republic, approximately half of the heat-related excess deaths associated with the severe 1994 heat waves likely would have occurred even without the unseasonable heat, as they were merely normal deaths that were simply hastened by a few days to a few weeks by unseasonably warm temperatures.

In the Netherlands, Huynen et al. (2001) evaluated the impact of heat waves and cold spells on mortality rates of people of all ages throughout the entire country for the 19-year period 1 January 1979 through 31 December 1997.  During heat waves they found a mean excess mortality of 39.8 deaths per day, while during cold spells they found a mean excess mortality of 46.6 deaths per day.  These numbers indicate that a typical cold-spell day kills at a rate that is 17% greater than a typical heat-wave day.  However, they also report that the heat waves of the period they studied ranged from 6 to 13 days in length, while the cold spells lasted from 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 their words, "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," which conclusion has also been reached by Kunst et al. (1993), Alberdi et al. (1998), Eng and Mercer (1998), as well as others mentioned in this Summary.  It is highly likely, therefore, that the 60% greater death toll we have calculated for Dutch cold spells 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 precisely 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, but a 67% drop in Dutch cold spells - they answered their own question, calculating a total mortality decrease of approximately 1100 people per year for the country at that point in time.

In concluding this Summary, we are forced to acknowledge the Great European Heat Wave of 2003.  In describing this event, Larsen (2003) declares that "a record heat wave scorched Europe in August 2003, claiming an estimated 35,000 lives."  Then, after rehashing some of the particulars of the meteorological event and reciting a bit of heat wave lore, she states "we can say with confidence that the August heat wave in Europe has broken all records for heat-induced human fatalities," and that "for many of the millions who suffered through these record heat waves and the relatives of the tens of thousands who died, cutting carbon emissions is becoming a pressing personal issue [our italics]."

To provide a rational as opposed to an emotional context for evaluating these claims, it is important to consider what occurs during the other extreme period of the year, i.e., winter.  According to the United Kingdom's Department of Health, as cited by McGregor et al. (2004), average winter excess mortality in a normal year in the UK alone is identical to what is claimed by Larsen to have required a heat wave of unprecedented proportions over all of Europe.  In addition, Stedman (2004) analyzed the impact of air pollutants during the 2003 heat wave in the United Kingdom and determined that 21-38% of the total excess deaths claimed to be due to high temperatures were actually the result of elevated concentrations of ozone and PM10.  Likewise, Fischer et al. (2004) determined that 33-50% of the deaths attributed to the same heat wave in the Netherlands were caused by high ozone and PM10 concentrations.  And when one accounts for the harvesting effect of the 2003 heat wave, its magnitude truly pales in comparison to the many run-of-the-mill cold spells that occur throughout Europe every single winter, cold spells whose killing power could be significantly reduced with but a modicum of global warming.

In conclusion, and in response to the question we posed at the start of this Summary (What is global warming doing to our health?), we can confidently state that it is helping us to preserve many more lives, which would otherwise be lost to the deadly effects of cold spells, than it is causing to be lost to the debilitating effects of heat waves, which clearly suggests that not cutting carbon emissions should become "a pressing personal issue" for everyone who cares anything at all about the welfare of humanity.

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Last updated 28 September 2005