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Climate Change, Correlation, Causation and gullible people

I have a natural skepticism of media releases attempting to use climate science as a rationale for public policies because these public policies have less to do with improving the health and welfare of the general public and everything to do with gaining and maintaining political power …

Let us remember that there is a difference between correlation (interrelated co-factors, both positive and negative) and causation (one of more co-factors causing an observed event); and the fact that correlation is not always causation. That is, because drug users all drink water, that water drinkers will become drug users. We should also remember that science is not performed by consensus and that the output of computer models is not scientific fact.

Therefore, I looked with great skepticism and disdain on a media release from Arizona State University’s College of Liberal Arts and Sciences.

flu

The American public can expect to add earlier and more severe flu seasons to the fallout from climate change, according to a research study published online Jan. 28 in PLOS Currents: Influenza

“It appears that fewer people contract influenza during warm winters, and this causes a major portion of the population to remain vulnerable into the next season, causing an early and strong emergence,” says Towers. “And when a flu season begins exceptionally early, much of the population has not had a chance to get vaccinated, potentially making that flu season even worse.”

The current flu season, which is still in high gear in parts of the nation, began early and fiercely. It followed a relatively light 2011-2012 season, which saw the lowest peak of flu since tracking efforts went into effect, and coincided with the fourth warmest winter on record. According to previous studies, flu transmission decreases in warm or humid conditions.

If global warming continues, warm winters will become more common, and the impact of flu will likely be more heavily felt, say the study’s authors. <Source>

From the actual papers …

(2013) Climate change and influenza: the likelihood of early and severe influenza seasons following warmer than average winters

Abstract

The 2012-13 influenza season had an unusually early and severe start in the US, succeeding the record mild 2011-12 influenza season, which occurred during the fourth warmest winter on record. Our analysis of climate and past US influenza epidemic seasons between 1997-98 to present indicates that warm winters tend to be followed by severe epidemics with early onset, and that these patterns are seen for both influenza A and B.

We posit that fewer people are infected with influenza during warm winters, thereby leaving an unnaturally large fraction of susceptible individuals in the population going into the next season, which can lead to early and severe epidemics.

In the event of continued global warming, warm winters such as that of 2011-12 are expected to occur more frequently. Our results thus suggest that expedited manufacture and distribution of influenza vaccines after mild winters has the potential to mitigate the severity of future influenza epidemics.

Citation: Towers S, Chowell G, Hameed R, Jastrebski M, Khan M, Meeks J, Mubayi A, Harris G. Climate change and influenza: the likelihood of early and severe influenza seasons following warmer than average winters. PLOS Currents Influenza. 2013 Jan 28 [last modified: 2013 Jan 29]. Edition 1. doi: 10.1371/currents.flu.3679b56a3a5313dc7c043fb944c6f138.

While it is nice to know that “warm winters tend to be followed by severe flu epidemics, I would be more impressed if the authors actually conducted research to indicate why this was true. Such a study was conducted in 2010 and is presented below.

Now, if you want to be impressed with something relevant …

(2010) Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States

Abstract

Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent reanalysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here, we extend these findings to the human population level, showing that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions.

Author’s Summary

The origin of seasonality in influenza transmission is both of palpable public health importance and basic scientific interest.

Here, we present statistical analyses and a mathematical model of epidemic influenza transmission that provide strong epidemiological evidence for the hypothesis that absolute humidity (AH) drives seasonal variations of influenza transmission in temperate regions.

We show that the onset of individual wintertime influenza epidemics is associated with anomalously low AH conditions throughout the United States.

In addition, we use AH to modulate the basic reproductive number of influenza within a mathematical model of influenza transmission and compare these simulations with observed excess pneumonia and influenza mortality.

These simulations capture key details of the observed seasonal cycle of influenza throughout the US. The results indicate that AH affects both the seasonality of influenza incidence and the timing of individual wintertime influenza outbreaks in temperate regions.

The association of anomalously low AH conditions with the onset of wintertime influenza outbreaks suggests that skillful, short-term probabilistic forecasts of epidemic influenza could be developed.

Citation: Shaman J, Pitzer VE, Viboud C, Grenfell BT, Lipsitch M (2010) Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States. PLoS Biol 8(2): e1000316. doi:10.1371/journal.pbio.1000316

This is the same type of study and modeling, but you will notice that there is no hype, and no bafflegab about “global warming.”

Bottom line …

There are many other factors that may have a significant effect on influenza-related mortality and should be considered in conjunction with the weather.

  • Since the severity of a flu season is measured by recorded mortalities, one might posit that the most vulnerable population, the elderly, will produce rising numbers independent of weather as the nation naturally ages. It appears that the elderly may also have the least benefit from seasonal flu vaccine formulations due to a variety of comorbidity conditions and other factors.
  • There is a natural error factor as deaths are attributed to influenza-like symptomology and not a verified flu strain.
  • That many people may become more vulnerable to the flu in the winter due to the stress of cold weather on their immune systems and a potential Vitamin D deficiency due to reduced sunlight that can also affect the body’s immune system and ability to ward off disease.
  • And that the CDC’s “best guess” as to the composition of the upcoming flu strains and the six-month lead time for mass vaccine production may also significantly alter outcomes.

Therefore, experimental work should be controlled for the above significant variables before high-probability correlations can be stated with some degree of certitude.

It should also be noted that I continue to be annoyed by those who continue to suggest that we should immediately implement draconian public policies based on incomplete and unsettled science. There is no planetary emergency and that the natural timescale of climate variability gives us a very, very long lead time when it comes to researching and understanding climate change. Probably best said as: if we stopped all energy and carbon production today, we would not be able to measure the results (if ever against the natural variability of climate change) for at least 600 to 1,000 years depending on the particular datasets used.

-- steve


“Nullius in verba.”-- take nobody's word for it!

“Beware of false knowledge; it is more dangerous than ignorance.”-- George Bernard Shaw

“Progressive, liberal, Socialist, Marxist, Democratic Socialist -- they are all COMMUNISTS.”

“The key to fighting the craziness of the progressives is to hold them responsible for their actions, not their intentions.” – OCS

"The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane." -- Marcus Aurelius

“A people that elect corrupt politicians, imposters, thieves, and traitors are not victims... but accomplices” -- George Orwell

“Fere libenter homines id quod volunt credunt." (The people gladly believe what they wish to.) ~Julius Caesar

“Describing the problem is quite different from knowing the solution. Except in politics." ~ OCS

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