Saturday, July 23, 2011

Hot or Cold

Suffice it to say Eli was a bit surprised to hear NOAA sources quoted recently (like about when the local temperature went up to boil) that heat causes more deaths than cold. This contradicted a bunch of earlier reports that he had internalized, so poking about the INTERNETs the bunny went.

About the best comment was on weather underground

The three 2008 studies for the U.S. show the ratio of cold deaths to heat deaths ranges from 2:1 to 1:3, which is very different from the 7:1 and 9:1 figures quoted by Will and Lomborg for Europe, India, and China. I don't trust any of these numbers, since heat and cold mortality statistics are highly uncertain and easy to cherry pick to show a desired result.
Counting the dead is not the problem, assigning the cause of death, heart attack, hypo or hyperthermia is. Kevin Borden and Susan Cutter take a shot at it, and evaluating a couple of previous publications, the results of which can be seen to the right. They conclude
Hazard mortality data are fraught with inconsistencies across databases. Differences manifest themselves from the subjective nature of attributing any death to a hazard event. Because of the lack of a standardized death classification scheme, hazard deaths are not counted in the same way for any two databases. In fact, even within a national database (i.e. SHELDUS, Compressed Mortality File), hazard death attribution likely varies geographically. Therefore, we are cautious that the analyses and conclusions drawn from hazard mortality data are based on estimates of deaths from natural events

There is considerable debate about which natural hazard is the most "deadly". According to our results, the answer is heat. But this finding could change depending on the data source, or how hazards within a data source are grouped, as we've shown here. Even if researchers could definitively assert the 'deadliest hazard,' a better issue to pose is where residents are more susceptible to fatalities from natural hazards within the United States.
because if you can answer that question, you can take precautions and improve infrastructure for dealing with the natural hazards. Of course, if you keep on piling greenhouse gases into the atmosphere, it is possible to make large portions of the earth uninhabitable in a couple of hundred years. But, as we say in the hutch, that's your problem


Anonymous said...

I think one key issue is whether flu & cold virus deaths are attributed to cold weather or not... if they are, then cold beats heat. If they aren't, then heat beats cold (at least, in the US).

The best epi study in the US that I'm aware of is Medina-Ramon & Schwartz: see, for example, which found that heat events were more deadly than cold events.

While I'm not sure the M-R & S paper points it out, I think the two statements above work well together: flu & cold deaths are probably not particularly exacerbated by extreme cold snaps, but are just general cold-weather sicknesses (possibly because cold viruses live better in the cold? Though I have vague recollection of hearing that the timing of flu season is actually based on when the virus gets here from Asia, which might suggest that the winter timing is more coincidence than cold related).


James Annan said...

Far more people die in the winter, but people are keen to attribute these to other causes. There's a lot more flu around, for example, but is this due to the "cold" or rather to a generally dark wet climate (and more time indoors), for example?

The real question is how death rates will change in a changing climate, and the big elephant in the room is how well we acclimatise to the changes (says the person who adjusted pretty well to about 10C summer warming in a matter of a few years).

Deech56 said...

I think both sides of the heat/cold are missing the point. I don't think the major problem that the world will face is necessarily acclimatization, but famine. Excessive cold and heat can kill thousands, but death tolls from famine can run into the millions.

Brian said...

The other issue is deaths attributable to increased pollution due to heat, particularly ozone. My impression, possibly wrong, is that pollution-caused mortality can result from cumulative exposure, so extra heat in the summer can kill anytime.

I agree though that the indirect effects (disease from cold, pollution from heat) are likely to outweigh direct effects.

J Bowers said...

Seem relevant:

Native animals 'just fell out of trees' during heatwave - January, 2010

The World’s Tropical Forests Are Already Feeling the Heat

seamus said...

Carrots for cogitation...

A Large Change in Temperature between Neighbouring Days Increases the Risk of Mortality
"Previous studies have found high temperatures increase the risk of mortality in summer. However, little is known about whether a sharp decrease or increase in temperature between neighbouring days has any effect on mortality."

Diurnal temperature range and daily mortality in Shanghai, China
"Although the relationship between temperature level and mortality outcomes has been well established, it is still unknown whether within-day variation in temperature, e.g. diurnal temperature range (DTR), is a risk factor for death independent of the corresponding temperature. Moreover, DTR is a meteorological indicator associated with global climate change which may be related to a variety of health outcomes."