Here in IN we think of a variety of dangerous weather: tornados from early spring through late fall, blizzards rarely, downdraft wind storms frequently, flooding, and lightning. But we, at least me, often ignore the most deadly weather event - heat.
The POTUS recently said "“The No. 1 weather-related killer is heat. 600 people die annually from its effects, more than from floods, hurricanes and tornadoes in America combined.”
It appears he may have been wrong. The number is probably higher.
However, the most deadly weather event is cold. For the United States Gasparini et al. found that 5.9% of deaths were attributable to high and low temperatures. Of those 5.5% were from cold and 0.4% from heat. Thus, cold was 15x deadlier than heat.
Excess winter mortality is an established global phenomena. It would be most unusual if it weren’t the case in the US. The link I gave above to the Lancet paper covered 384 locations in 13 countries.
A later study by Zhao et al. covered 750 locations in 43 countries. It found cold-related deaths outnumbered heat-related deaths by a factor of 9.3x.
Three months ago Masselot et al. published a paper that examined excess mortality attributed to heat and cold in 854 European cities. Cold-related deaths outnumbered heat-related deaths by a factor of 10.1x.
While open to discussion of the details, many studies in many countries and cities have shown the same pattern – cold kills more people than heat.
Deschenes and Moretti found an interesting result when looking at the cause of death in county records for almost 3000 US counties. In addition to higher mortality rates in the winter, they found different patterns in deaths after days of extreme hot or cold temperatures.
There is spike in deaths during a heat wave, not surprisingly concentrated in older individuals. The authors write, “Remarkably, however, almost all of this excess mortality is explained by near-term displacement. In the weeks that follow a heat wave, we find a marked decline in mortality hazard. This decline completely offsets the increase during the days of the heat wave. As a consequence, there is virtually no lasting impact of heat waves on mortality.”
In contrast, they found a significant and long-lasting effect on life expectancy from cold. After the spike in cold deaths there is no offsetting decline in the following weeks.
How are cold versus hot effects relevant if the cold extremes AND the hot extremes are both caused by human activity? That’s why they changed it to “global climate change” instead of the old style “global warming”.
In the most recent IPCC report (AR6) there is a table on what climate effects have risen above the noise of natural variation (Working Group 1, Chapter 12, Table 12.12). Found here on page 1856)
One of the categories is “cold spell”. Unfortunately I couldn’t find where they define what that is, but at any rate it is highlighted in yellow, indicating a decreasing trend of medium confidence. They note this applies to Australia, Africa and most of Northern South America.
It is possible that you are both right and also both wrong. It all depends on how you count the numbers and what numbers are counted. Here are just a few potential complications:
One has to look at what populations are being surveyed. For example, extreme weather mortality in northern Europe will probably be dominated cold-related deaths while Mediterranean populations will be more impacted by abnormal high temps. This would be an example of sampling bias.
Deaths tend to be more frequent during the winter because of stuff like influenza and icy roads that occur independent of extreme cold conditions. This could lead to an overcount of cold-related deaths.
Many countries expected to be most impacted by high temperatures have inconsistent medical record keeping. This would include much of Africa, central Asia, and Central America. This would tend to undercount heat death.
Weather Underground has a good discussion on the issue, noting that the NOAA sees more heat-related deaths while the CDC reports the opposite. Over the short term, it appears that abnormal heat has a stronger immediate impact on mortality, causing a spike in excess deaths not seen with analogous cold spells. Which Kills More People: Extreme Heat or Extreme Cold? | Weather Underground
For a more detailed description of how methodology matters:
It describes examples of the variation between studies:
A recent analysis of U.S. deaths from temperature extremes based on death records found an average of approximately 1,300 deaths per year from 2006 to 2010 coded as resulting from extreme cold exposures, and 670 deaths per year coded as resulting from exposure to extreme heat. These results, and those from all similar studies that rely solely on coding within medical records to determine cause of deaths, will underestimate the actual number of deaths due to extreme temperatures., For example, some statistical approaches estimate that more than 1,300 deaths per year in the United States are due to extreme heat. , Different approaches to attributing cause of death lead to differences in the relative number of deaths attributed to heat and cold. Studies based on statistical approaches have found that, despite a larger number of deaths being coded as related to extreme cold rather than extreme heat, and a larger mortality rate in winter overall, the relationship between mortality and an additional day of extreme heat is generally much larger than the relationship between mortality and an additional day of extreme cold.
I wonder if that might be due in some part to humans general diurnal nature - active during daylight hours and resting at night. We tend to be out and about during what is usually the warmest part of the day. When cold is the issue, that’s a good thing. When heat is the issue, it’s not.