Background
Referencing the Fourth Assessment Report of the IPCC, the authors write that "temperature, a key climate change indicator, is expected to increase substantially in the Northern Hemisphere, with potentially grave implications for human health."

What was done
Concerned about what these "expectations" might mean for their homeland, the five Danish researchers investigated the association between the daily three-hour maximum apparent temperature (which reflects the physiological experience of combined exposure to humidity and temperature) and deaths due to cardiovascular disease (CVD), cerebrovascular disease (CBD) and respiratory disease (RD) in the nation's capital, Copenhagen, over the period 1999-2006.

What was learned
Wichmann et al. found -- during the warm half of the year (April-September) -- that a rise in temperature actually had an inverse or protective effect with respect to CVD mortality (a 1% decrease in death in response to a 1°C increase in apparent temperature), which finding is rather unusual but has also been observed in Dublin, Ireland, as reported by Baccini et al. (2008, 2011), while they found no association with RD and CBD mortality. And at the other end of the thermal spectrum, during the cold half of the year, all three associations were inverse or protective, which finding, according to the researchers, is "consistent with other studies (Eurowinter Group, 1997; Nafstad et al., 2001; Braga et al., 2002; O'Neill et al., 2003; Analitis et al., 2008)."

What it means
Whereas climate alarmists continue to emphasize the primarily negative impact of summer heat waves on human death rates in low- and mid-latitude regions of the earth, essentially neglecting to report what happens there during winter cold spells, Wichmann et al.'s summer results tell a dramatically different story that is likely typical of higher latitudes. And they additionally portray what tends to happen nearly everywhere in winter, noting that during that cold part of the year "only protective effects [of warming] were observed," as may readily be seen to also be the case throughout the world by perusing the materials we have archived in our Subject Index under the general heading of Health Effects (Temperature -- Hot vs. Cold Weather), where the number of warming-induced deaths avoided in winter significantly over compensates for the number of deaths caused by an equivalent warming in summer.

References
Analitis, A., Katsouyanni, K., Biggeri, A., Baccini, M., Forsberg, B., Bisanti, L., Kirchmayer, U., Ballester, F., Cadum, E., Goodman, P.B., Hojs, A., Sunyer, J., Tiittanen, P. and Michelozzi, P. 2008. Effects of cold weather on mortality: Results from 15 European cities within the PHEWE project. American Journal of Epidemiology 168: 1397-1408.

Baccini, M., Biggeri, A., Accetta, G., Kosatsky, T., Katsouyanni, K., Analitis, A., Anderson, H.R., Bisanti, L., D'Ippoliti, D., Danova, J., Forsberg, B., Medina, S., Paldy, A., Rabczenko, D., Schindler, C. and Michelozzi, P. 2008. Heat effects on mortality in 15 European cities. Epidemiology 19: 711-719.

Baccini, M., Tom, K. and Biggeri, A. 2011. Impact of heat on mortality in 15 European cities: Attributable deaths under different weather scenarios. Journal of Epidemiology and Community Health 65: 64-70.

Braga, A., Zanobetti, A. and Schwartz, J. 2002. The effect of weather on respiratory and cardiovascular deaths in 12 US cities. Environmental Health Perspectives 110: 859-863.

Eurowinter Group. 1997. Cold exposure and winter mortality from ischaemic heart disease, cerebrovascular disease, respiratory disease, and all causes in warm and cold regions of Europe. The Lancet 349: 1341-1346.

Nafstad, P., Skrondal, A. and Bjertness, E. 2001. Mortality and temperature in Oslo, Norway, 1990-1995. European Journal of Epidemiology 17: 621-627.

O'Neill, M.S., Zanobetti, A. and Schwartz, J. 2003. Modifiers of the temperature and mortality association in seven US cities. American Journal of Epidemiology 157: 1074-1082.