Why is Australia in drought again?

Australia’s weather is highly variable year to year, because we are a very large island surrounded by very large oceans.

Droughts are quite common. But they aren’t increasing, Bureau of Meteorology data shows that over the past one hundred years there is no trend in frequency of droughts. Contrary to intuition, and popular belief, global warming hasn’t made Australia drier. Climate scientists say it might, but equally it might make Australia wetter, it’s an unknown at the moment. From what we know today about Australia’s climate, global warming is unlikely to make much change in the drought situation.











In 2019 we are back in drought again, well in much of the country. It’s usually like this, some parts in drought others not.

2014 a strong El Nino effect started. This usually reduces rainfall over Eastern Australia. Which is what happened. Now the good news is that this has subsided. Unfortunately another big influence on Australian climate is the Indian Ocean Dipole, this year it switched into a strong positive phase. This means cooler than usual water off Australia’s NorthWest. This cooler water in the Indian Ocean means less humidity and less rain over much of Australia (mostly where all the people live).

So all of the non-tropical part of Australia has been hit with a double whammy.

No it’s not climate change. This is our climate.

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Why I changed my mind about… global warming.

Most, if not all, people would consider themselves to be open-minded.  Yet, if you ask someone to name an important belief that they have changed their mind about, in response to evidence and/or logic, most struggle to give even one example.

This is the first in a series of blogs where I describe how and why I changed my mind about something.  I hope to encourage myself to change my mind more often.  And to encourage others.

Short summary: I now worry less about global warming than I did, the scientific evidence is that it’s not going to be catastrophic.  PS Our best course of action is to adapt to the effects and to invest in R&D to develop new low carbon energy.

I’ve been a “greenie” since I was a child.  I raised money and marched to save the whales.  I searched out all the pockets of native bush on our New Zealand farm.  I became a vegetarian (although the original motivation was nutritional, not for the environment).  As an adult I bought hundreds of acres of Australian bush (mallee) land and have set it aside to regenerate.  When I learnt that greenhouse gas emissions were causing the climate to warm I put solar panels on the roof of my house, I sold my car and lived without one for years (until having a new baby made that impractical so I bought a small car and ran it on bio-diesel (I couldn’t afford a Prius)).

When Al Gore’s 2006 movie came out about global warming I used it to to rally my colleagues in the Ehrenberg-Bass Institute – “how could we contribute to the solution?” I asked.  Being a complex problem I didn’t think it was likely it would be solved simply by legislation or technology, and I thought that we might contribute insights into consumer behaviour as well as mass communication effectiveness.  Some of my colleagues pushed back (we have a culture of questioning, and not just accepting things that the director says).  They said that Al Gore was exaggerating, that he sounded more like a religious zealot than a scientist, and pointed out the numerous errors he presented.  I agreed, but I said he is a (religious) politician with good intentions, he’s inflating things to get attention.  I quoted them more technical accounts of global warming from people like Tim Flannery (a mammalogist, author of The Weather Makers (2005)).

But then the forecasting scientists in the Institute told me that the forecasts of global warming were not to be trusted.  They pointed out that climate scientists were not forecasting scientists, that climate scientists were ignorant of the established principles that help improve the very difficult business of making forecasts (ie predicting the future) in complex conditions, and that their forecasting approaches were a very long way from best practice.  It’s common for experts in a field (finance, politics, physics) to assume that their expertise means they can make better forecasts than non-experts.  However, research on forecasting accuracy has shown over and over that this is not true, experts are merely more sure of their forecasts, but no more accurate.

So now I had a dilemma.  I respected the forecasting scientists, but I also respected the climate scientists. And emotionally I really like the idea that this global challenge might be discovered by science and then solved in a globally coordinated manner – it would be a sign of how advanced human civilization had become, and a real feather in the cap of science.

“But look at your own field”, said the forecasting scientists… “what do you think of the consensus of views among marketing academics, do you think this represents real knowledge or rather “group think?”  Ouch.

Plus I knew that complex multivariate models in marketing (and elsewhere) have a miserable track record in making predictions, even in quite stable environments.

Oh dear.  They certainly gave me doubts… but time will help decide things I thought, as we would see the prediction of the climate models borne out at a global scale.  Indeed, in 2007 Professor Scott Armstrong challenged Al Gore to a 10 year global warming forecast competition.  The losing forecaster would make a donation to charity.  Al Gore declined to participate but the competition went ahead regardless.  Based on the forecasting principle of “be conservative” Scott Armstrong proposed a ‘no change’ forecast, which was a bit radical given that everyone knew the climate was warming slowly.  The competition wasn’t compared to Al Gore’s dramatic “tipping point” forecast, but instead to the more accepted IPCC forecast of 3 degrees of warming over the next 100 years.  Ten years later and Scott Armstrong’s forecast turned out to be more accurate.

Now ten years isn’t long enough to be definitive, but it’s important because it was a predictive test.  Modellers love to play with their models, tweaking this and that, trying to get better and better fits to historic data (achieving lots of academic publications and grants along the way).  This sounds sensible but there is a very high risk of “over fitting” where the model is modelling noise/error in the data, so the fit to historic data is better but it’s even worse at predicting the future, and therefore not correctly telling us what really causes what.  The IPCC’s has done an assessment of climate models, which is a bit like marking your own homework but even they reported that almost every model failed to predict the slowdown in warming that occurred after 1998, in other words the models predicted more warming than occurred.

Climate scientists are now working out why their predictions were wrong,

The discrepancy between simulated and observed GMST trends during 1998–2012 could be explained in part by a tendency for some CMIP5 models to simulate stronger warming in response to increases in greenhouse gas (GHG) concentration than is consistent with observations (Section, Figure 10.4)

and how to improve them (some climate scientists claim that with a better understanding of multi-decade variations in speed of warming “the long-term warming trend in response to human emission of greenhouse gases is found remarkably steady since 1910 at 0.07°–0.08°C decade“).

Time will tell, but for now it’s clearly good news that the climate doesn’t seem to have reacted to greenhouse gases quite the way we feared.

Meanwhile there is other evidence that has changed my mind about the seriousness of global warming and the best courses of action to take to mediate its effects.  It’s not that global warming isn’t a problem, but the problem has been misrepresented, and over-hyped (by people with good intentions).  And simplistic, unfeasible solutions have been embraced, while more feasible zero-carbon solutions such as nuclear power are mostly  ignored.  Most concerning is how preoccupied people are about “what side you are on?” rather than wanting to discuss facts.

Global warming is not a existential threat.  Global warming means the world is getting hotter (milder winters, hotter summers).  Which is of most concern for those who already live in hot places (like Adelaide or Dubai) but probably quite welcome if you live in Northern Europe, China, or America.  Each year far more people die due to cold than from heat, even in Australia six times more deaths are due to cold than heat.  And most of this isn’t from extremes but rather simply cold winters, and global warming means warmer winters (that’s something the climate scientists all agree upon).

Contrary to reports in the popular press, climate scientists have not been reporting more hurricanes, flood, fires and so on due to Global Warming.  There are concerns that extreme weather events might increase but not for a long while yet, and maybe not.  Equally importantly United Nations data shows that deaths due to extreme weather events have declined a staggering 96% over the past century, and that’s in spite of population growth.  Why? How? Largely due to better buildings and infrastructure, better emergency services, better hospitals and so on.  In other words, human technology and wealth levels, both of which continue to improve.  So even predictions of increased deaths due to a warmer planet seem far fetched, while the idea that global warming means “the end is nigh” is sheer apocalyptic fantasy.

This is pretty important to know because there are many things we’d like to fix (literacy, poverty, antibiotic resistant bacteria, cancer, clean water, endangered species etc), and efforts and money put into one problem often does nothing for another.  We need to have a proper sense of the magnitude of each threat, each problem, and then the options to solve the problem and what their costs and feasibility are.

Anyway, decide for yourself, be open-minded.  Here are a few oimportant climate science articles that don’t get much coverage in newspapers (which prefer bad news):

The world is getting substantially greener.  This is a positive effect of CO2.  Also as the world become richer (and cleverer) people stop cutting down forests, and start planting trees.

Wildfires are not increasing, “Instead, global area burned appears to have overall declined over past decades, and there is increasing evidence that there is less fire in the global landscape today than centuries ago”.  Globally, the total acreage burned by fires declined 24 percent between 1998 and 2015.  It appears that changes in agricultural practices are more than offsetting the increased fire risk now that they world is 1 degree warmer.

The world’s beaches are not disappearing.  Most are stable, some are shrinking, but slightly more are growing.  And Pacific and Indian Ocean atolls aren’t shrinking.

Oceans are rising.  This article says the trend is less than 2mm a year (or 20 centimeters per Century).  Here is an article where a climate scientist explains the error of newspapers of reporting the very unlikely forecast of a one metre rise this Century.

There has been no increase in North Atlantic tropical cyclone flooding.  Nor tornadoes in the USA.  Tropical cyclones in Australia tend to also show a small declining trend.

NASA says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.

And even though most Australians believe that there are more droughts, there is actually no drying trend over the past hundred years, according to Bureau of Meteorology data.  Professor Andy Pitman (Director of the Australian Research Council Centre of Excellence for Climate Extremes, and a Lead Author for the IPCC) says there is no reason to think global warming will cause more droughts in Australia (at 1hr, 11 minutes).

So because of the evidence, I’ve gone from being a climate alarmist to a climate realist.  I hope that both ‘alarmists’ and ‘deniers’ will do likewise.  Then we can all move on to working out feasible solutions that don’t harm people and the environment while trying to save them.

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Actually, “the rich” already pay most of the tax

I was recently told by someone that they thought Australia needed to tax the rich more.  I asked how much of the government’s tax take they felt should be paid by the top 10% of income earners.  They didn’t give a figure because they didn’t know what it was currently. Nor did I so I went and looked up the evidence.  It turns out that, in Australia:

1) The top 10% of income earners pay 50% of the income tax.
2) Average income tax rates (%) are 15 times higher for the top 20% of households than the bottom 20%.
3) Half of households make pay no net tax (ie tax minus welfare payments).
4) 80% of households receive more from the government than they pay.

Firstly, the top 10% of Australian workers pay about 50% of all income tax that the government receives. About half of this (27%) is paid by the top 3% of earners. So clearly, well paid Australian workers have an awful lot of tax taken out of their pay packet. The Tax Office reports that the highest paid (and taxed) are surgeons. Other professions in the top 10 include anaesthetists, GPs, psychiatrists, and mining engineers. CEOs came in at number 9.

But this is just income tax, people also pay other taxes (eg GST). And they receive money back from the government (eg pensions, welfare). When looking at this complete picture, it turns out that half of all households make no net contribution at all. While the other households provide all the funding of public schooling, hospitals, housing, ABC, SBS etc.

All of us benefit from this government spending on parks, schools, medicare. When this benefit is taken into account only 20% of households (in any year) pay any net tax.

Only the top fifth of households ranked by their income – those with incomes of more than $200,000 a year in the financial year ending June 2012 – pay anything into the system net of the value of social security in cash and kind received, according to data from the latest Australian Bureau of Statistics survey of household income.

One author writes: “the rich don’t pay a “fair share” of tax…. they pay all of it“, but this is a bit of a distortion, they don’t pay all of it, they are just the only ones who pay more than they receive, and they pay a very great amount.

Clearly we take a lot of tax from high earners, and give it to low earners. So any Australian politician who promises to give you more by taking more from the rich is being deceitful – they already pay so much. This is one of the reasons that Treasury analysis always shows that increased taxes on the wealthy will raise very little money.

PS This is an analysis of people who earn incomes. There are a few people who are rich but don’t earn incomes so don’t pay a lot of tax, e.g. a widow living in a mansion, a university student living off parents, a farmer whose farm lost money in this particular year.

According to Australian Bureau of Statistics, the middle quintile of Australian households receive $2.70 in cash and services for every $1 they paid in tax. How can this be? Because the top quintile (20%) pays a lot, also the govt receives corporate taxes.

The biggest corporate taxpayers are the mining/oil companies, banks, and Coles and Woolworths.

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Everything is subjective, but don’t worry about it

Outside of mathematics, geometry, and logic everything is subjective.  That is, anything about the empirical world is subjective, because we experience the real world through our (fallible, subjective) senses.  But, and it is a very big but, this isn’t the worry that some people think it is.

It’s not uncommon to hear statements like “everything is opinion”, “everyone’s opinion is as valuable as anyone else’s”, “it’s all just theory”, “science can’t prove anything”, “anyone can make the data say what they want it to say”, and so on.  You get the gist, the idea is common yet extreme – that subjectivity means that “anything goes”.

Everything is subjective, and science can’t prove anything in the same way we can develop logical or mathematical proofs.  But this doesn’t mean ‘anything goes”.  Facts exist, they are things that are inter-subjectively certifiable, that is, that multiple different people using their subjective senses all “see” the same thing.  This is why no sensible people argue about statements like “the sky is blue”, “elephants are heavier than mice” and so on.  There are billions of things that are known with a certainty that, for all practical purposes, can be relied upon.

Some explanations are also vastly superior, in that they fit with the currently known facts while other explanations don’t.  And if two explanations both fit with the facts then we prefer the more simple explanation (for good reasons, see Occam’s Razor).  Eventually our explanation may be replaced with a better one, that fits more facts or new facts, or with greater simplicity.  The important point is that, in spite of our subjectivity, some explanations are better than others – it isn’t “anything goes”, not everyone is right.

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Why people (on the left and right) love conspiracies

“It was because he wanted there to be conspirators. It was much better to imagine men in some smoky room somewhere, made mad and cynical by privilege and power, plotting over the brandy. You had to cling to this sort of image, because if you didn’t then you might have to face the fact that bad things happened because ordinary people, the kind who brushed the dog and told their children bedtime stories, were capable of then going out and doing horrible things to other ordinary people. It was so much easier to blame it on Them. It was bleakly depressing to think that They were Us. If it was Them, then nothing was anyone’s fault. If it was Us, what did that make Me? After all, I’m one of Us. I must be. I’ve certainly never thought of myself as one of Them. No one ever thinks of themselves as one of Them. We’re always one of Us. It’s Them that do the bad things.”

Excerpt From

Terry Pratchett

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Zealotry, closed-mindedness

An extreme case is when someone says “no fact, no information could make me change my mind”.

A less extreme, and vastly more common, position is along the lines of “I would rather not listen to information that might lead me to reconsider” or “I will avoid, certainly not not seek out such information/views”. Or “I’ll ignore… deliberately not give this thinking time”.

And then there is “I’ll think ill of you if you say things that unsettle my beliefs. I’ll be offended by you.”

Or, even worse, “I’ll try to very hard to discredit you if you say things that unsettle my beliefs”.

Scientists, of all people, should be the most immune to this sort of thinking, but of course we are human, so not completely immune. Zealotry, closed mindedness, is something everyone needs work consciously to avoid.

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Does alcohol cause cancer ?

by Professor Byron Sharp

short answer: The scientific evidence is that alcohol helps cause (only) two cancers: aerodigestive and liver.  These are rare causes of death, so the increased chance that drinkers will die from these cancers is tiny.  A very large body of evidence continues to support a causal association between moderate drinking and longer life, due largely from less risk of diabetes and less risk of dying from heart disease.

sub-title: Can Good Intentions Corrupt Science?

Recently an article by a Kiwi Professor gained global press coverage with sensational headlines along the lines of “proof that alcohol causes cancer”.  This is a very significant claim which therefore deserves significant scrutiny.  Unfortunately in this case I’m afraid that there has been an abuse of science.  I’m very interested in the corruption of science, and science communication.  This doesn’t always arise from corrupt individuals – more common causes of  bias are good intentions, moral vanity, and a desire to please a dominant funding body.  That’s what it looks like here: perhaps a case of seeing what you want to see in the evidence, or perhaps even deliberately misusing the evidence to achieve a social/political objective (‘the ends justifies the means’)?

The scientific evidence suggests alcohol helps cause (only) two cancers, areodigestive and liver, though these are rare and the elevated risk of death is tiny.  It’s wrong and unethical to scare the public, and to misrepresent the medical evidence.

I’m going to document how Professor Jennie Connor’s article missed out important studies and misrepresented others (she even missed evidence that helps a part of her argument).

Connor’s Assertion

Connor’s conclusions are not based on new data, nor data analysis.  Her article was published in the journal Addiction‘s “for debate” section.  The article’s purpose was to examine whether it might be reasonable to consider the (weak) correlations seen in population studies as causal evidence that drinking alcohol increases your risk of cancer.

Connor says alcohol causes some cancers.  This conclusion is based almost entirely on epidemiological studies that show that in surveys of populations drinkers have slightly higher rates of some specific cancers (and slightly lower rates of a few others).  In doing so she places great faith in epidemiology, far more than many of her colleagues.  A more sober analysis would adopt the epidemiologists’ rule of not considering risk estimates of less than a factor of 3 as indicating any causality (see Taubes 1995 ‘Epidemiology faces its limits’, Science, 269:5221, 164-69), e.g. smokers  have more than 20 times the risk of lung cancer.   Unlike smoking, alcohol-cancer studies seldom report risk estimates anywhere near a factor of 3.

The well known problem with epidemiology studies is that they show correlations that are often not causal – they can be completely spurious due to confounding factors.  For example, population data might show that elderly people who exercise regularly tend to live longer.  But elderly people who are afflicted with debilitating health issues are very likely to exercise less (many will be simply unable to undertake exercise), so really it is health that is determining both the exercise as well as the longevity.  Exercise might well be doing good but the risk estimate (for not exercising) is going to be inflated.

The problem with comparing alcohol drinkers, of various levels, to lifetime non-drinkers is that alcohol drinkers tend to smoke more, and they also tend to be less likely to live in rural areas and more likely to be wealthier.  Moderate drinkers might be people who tend to be adopt other healthy behaviours, while heavy drinkers may be self-medicating because of mental or physical ill-health.  The ability for statistics to control for such confounding correlations is rather poor.  So there are plenty of reasons for caution in treating a correlation seen in population data as causal.  Here are some funny examples of real but non causal correlations.

Connor understands that confounds produce spurious correlations yet refrains from discussing any likely confounds in her assessment of whether alcohol causes cancer.  Instead she goes off on a tangent discussing possible confounds for the well established link between drinking and a (substantially) lower risk of heart disease.  Here she suddenly loses her faith in epidemiology, i.e. when she doesn’t like the results.  For Connor to even discuss heart disease is rather odd, given that her article is about cancer.  And to discuss confounds for heart protection but then to dismiss potential confounds for her claimed causal link with cancer is at best an abrogation of scientific scepticism.

Inferring Causality

In the absence of controlled experiments (which for cancer research are pretty much impossible for ethical and practical reasons) we need other evidence to support treating a correlation in population studies as causal.  Connor’s article makes 3 such points:

1. First, Connor says, there is a dose-response relationship between alcohol consumption and some cancers, that is, any increase in drinking is associated with increased cancer risk.  However, she then (rightly so) contradicts herself in pointing out that for most of these cancers meta-analysis shows no risk for light drinking.  Connor should have noted that some meta-analyses show heightened risk only for the heaviest level of persistent drinking (which is problematic, as this group may contain alcoholics and people drinking as self-medication for health problems, a confound completely ignored by Connor (and many others)).

2. Second, Connor notes “evidence that, for some cancers, the risk associated with alcohol attenuates when drinking ceases”.  Now this is what we would expect if there were a causal relationship, yet it is odd that in such population studies the correlation between drinking and cancer risk drops so slowly, taking decades before drinking cessation results in the small elevated risk subsiding to that of a non-drinker.  This suggests the apparent alcohol risks have more to do with confounding factors than a direct causal relationship (i.e. lifestyle factors that slowly regress to the mean).  Regardless, this evidence is of poor quality, to quote from one of the meta-analyses that Connor references “Too few studies have addressed this question, and of the studies that have, all have significant limitations” and further “the only statistically significant relationship that we observe is that drinkers who recently quit drinking have a higher risk of liver cancer than current drinkers”.  It would  be wrong to make much of this evidence, because the models have huge error margins, and anyway they are hardly supportive of a causal link between alcohol and cancer.

3. Third, Connor briefly discusses potential biological mechanisms for how alcohol might cause cancer.  Alcohol in itself is not carcinogenic to human cells, and the epidemiology shows associations with only some cancers and not others (indeed, drinking appears to be protective against some cancers).  As Connor writes: “The mechanisms by which alcohol causes cancer are not well understood, but are thought to depend upon the target organ. Pure ethanol does not act as a carcinogen in animal studies, and evidence that it causes mutations directly in humans is weak”.  A possible mechanism is that bacteria in the mouth and digestive tract convert alcohol to acetaldehyde, which is a carcinogen.  As Connor notes “Stronger associations and more susceptibility at low doses is seen for the cancers where alcohol and [hence] acetaldehyde come into direct contact with the tissues”.  She doesn’t mention that this potential bio-mechanism is supported by the evidence that people whose genes mean they are slow to break down acetaldehyde (somewhat common in Asia, very rare for West Europeans), have substantially higher rates of oral/throat (aerodigestive) cancers.  Other potential biological mechanisms, such as alcohol increasing estrogen levels, remain very speculative and face a number of difficulties, such as explaining why women who drink alcohol have lower, not higher, rates of endometrial cancer (Je et al 2014, Sun et al 2010).

So for aerodigestive cancers, we see the highest correlations in epidemiology data (though nowhere like the magnitude for smoking), and we have a plausible mechanism (the culprit being acetaldehyde).  Plus we can add the evidence that Connor missed – there are much higher rates of aerodigestive cancer among people who do not have the genes to quickly metabolise acetaldehyde (Seitz and Becker 2007).  This is by far the best case for making a causal connection between drinking alcohol and a cancer.  Though it must be noted that aerodigestive cancers are rare (eg a tiny 0.3% of US deaths are from oral cancers, and most of these are caused by smoking, age and genes) – even though most of the population drinks alcohol.

For the other cancers Connor mentions, the evidence of causality is extremely poor.  In contrast, the evidence is vastly more convincing that drinking alcohol moderately reduces heart disease, diabetes, dementia, and overall mortality.  In addition to meta-analyses of  many population studies, we have plausible biological mechanisms, supported by lab studies, animal experiments, and hospital trials.  Meta-analysis of dozens of experiments shows administering alcohol to subjects leads to rapid positive changes in biomarkers for heart health (Brien et al 2011).  We also see changes in drinking linked to changes in rates of heart disease, diabetes and overall mortality, e.g. people who increase their drinking lower their risk of heart disease.  In sum, this is what a plausible case for causality looks like.

So apart from aerodigestive and perhaps liver cancer, Connor is wrong, the evidence does not support the hypothesis that drinking alcohol causes cancer.  And even for oral/throat cancer, the risk may be confined to smokers and people with particular ALDH enzyme mutations.

Alcohol does not increase risk of dying from breast cancer

But that’s if we stop with Connor’s superficial analysis.  There is more evidence to consider if we are to form a proper judgement about causality.  Read on…

Connor concluded that drinking probably was causal for 7 cancers.  This has a nice ring about it…. like the 7 Deadly Sins.  Now, Connor used the old medical convention of labeling cancer according to where the tumour occurs.  It’s possible to talk of hundreds if not thousands of different cancers, but more reasonably it’s not seven.  It’s actually (1) oral/throat/oesophagus (aerodigestive cancers) which we have already discussed, (2) liver, (3) colorectal, and (4) breast cancer.  It’s this last one that drives most public health forecasts that reductions in drinking will reduce cancer deaths.  This is because breast cancer is the most common potentially deadly cancer for women.  That said, less than 3% of female deaths in the USA are from breast cancer.  90% of breast cancer diagnoses turn out not to be fatal, due to curative treatment but also because many breast cancer diagnoses are for non-fatal cancer – ‘over-diagnosis’ is a very real problem.

Breast cancer is a prime example of why Connor should have discussed evidence on confounding factors, and should have distinguished between diagnosis and mortality statistics.  Meta-analysis shows no link between drinking and breast cancer mortality (Thun et al 1997, Fuchs et al 1995) while studies of those diagnosed with breast cancer also show no increased chance of death, nor with recurrence for drinkers (Gou et al 2013).  A new study from the Women’s Health Initiative (Lowry 2016) again shows no link between mortality and drinking before or after breast cancer diagnosis.  A smaller US study published in the same year showed the same thing, women who drank (at all levels from 1-36 standard drinks per week) before their breast cancer diagnosis had no higher risk of dying from the cancer than the non-drinkers (Din et al 2016).  Similarly a large study with long follow-up of women with breast cancer (Newcomb et al 2013) showed breast cancer patients had better chances of survival if they were regular drinkers before diagnosis.  If they altered their drinking after diagnosis this did not alter their chance of dying from breast cancer.  But an increase in drinking was associated with an overall increase in life expectancy (largely due to substantially fewer heart disease deaths among those who increased their alcohol consumption).  This is strong causal evidence that alcohol prevents heart disease, and it seriously conflicts with the idea that alcohol causes breast cancer.

Similarly while animal experiments show that alcohol consumption results in less heart disease, and longer life overall, they do not show a link between alcohol consumption and breast cancer (see Hackney et al 1992, Singletary 1997).  Alcohol actually reduced the risk of breast cancer metastasis in mice (Vorderstrasse et al 2012).

The (weak) correlation seen in population studies between drinking and breast cancer diagnosis is then probably due to a confounding factor, as so often can happen in population studies.  In this case it is probably simply that drinkers are more likely to screen for breast cancer (shown in Mu and Mukamal 2016) – screening definitely increases diagnosis.  Women from lower socio-economic superbs are less likely to drink and less likely to be screened for cancers (see here).  Land et al 2014, which screened all their subjects (i.e. controlling for screening incidence), showed no link between drinking and breast cancer – indeed drinking was associated with slightly less risk of diagnosis (of both breast and colon cancer).

Colorectal cancer?

The modest degree of increased risk of colorectal cancer for alcohol drinkers may also be spurious or exaggerated for the same reason – drinkers screen more, which results in more diagnoses.  Thun et al 1997 shows exactly the same low chance of developing colorectal cancer irrespective of drinking, for men and women.

As far as a potential biological mechanism, some fecal bacteria have been shown (in lab studies) to convert alcohol to acetaldehyde (Jokelainen et al 1994).  But then other bacteria have been shown to break down acetaldehyde (Nosova et al 2000) – the flora of the human gut are complex and not well researched.  Acetaldehyde has been shown to exist in the colons of rats but the level was not affected by feeding the rats alcohol (Seitz et al 1990).  Research is needed to see if drinking really can increase acetaldehyde levels in the colon.  In humans alcohol is absorbed in the stomach and small intestine which makes it harder to explain how alcohol might reach the colon where it might be converted to acetaldehyde by bacteria.  Whereas the risk of oral cancer is much higher among people without the genes to produce some acetaldehyde processing enzymes, this does not appear to be the case for colorectal cancer (Tiemersma et al 2003) (though the link between drinking and colorectal cancer is highest in Asian studies while barely statistically significant in Europe/America/Australia (Fedirko et al 2011)).  So a causal link between drinking alcohol and colorectal cancer remains speculative, and if there is a link, it is not strong – drinkers still get colorectal cancer at much the same rate as non/rare drinkers.

Liver Cancer?

That leaves us only with liver cancer remaining to be discussed.  This is a rare but deadly cancer, causing 1% of deaths in the USA, though most cases are due to viral infection (hepatitis), then obesity, diabetes, other disease, and genetics.  We perhaps again have the plausible biological mechanism of acetaldehyde but only at high levels of drinking as the liver is very efficient and fast at breaking down acetaldehyde.   It’s more plausible that alcohol, through its effect on liver disease, leads to higher risk of liver cancer.  However very few drinkers develop liver disease, so the degree of absolute increase in risk in absolute terms is tiny and probably only for long-term alcoholics or those unlucky enough to have liver damage from hepatitis or other causes.

Alcohol is a surprisingly benign hepatotoxin (i.e. the liver is remarkably good at dealing with it).  In mice and rat laboratory studies it isn’t possible to induce cirrhosis from alcohol alone, and this may be the case for humans as well.


Drinkers live longer.  Do they die more from cancer?

So it’s plausible that alcohol contributes to two cancers, both rather rare, and its influence can’t be great.  If this conclusion is correct then we would not expect drinkers to die much more often from cancer, and this is exactly what is observed in longitudinal population studies.  Meta-analyses of mortality studies report cancer death is barely higher among drinkers than occasional/zero drinkers, and confined to the cohort who admit to consumption of more than 50g of alcohol per day (see Jin et al 2012, table 2) which is very probably an under-estimate of actual consumption.  In Thun et al 1997 (a study of death among middle class, middle aged and elderly Americans) the heaviest drinkers showed higher rates of death from alcoholism and injury, as expected; they were also more likely to die from aerodigestive and liver cancer, again as we now expect, though none of these deaths were common; as expected, they were less likely than non/light drinkers to die from heart disease, stroke and other circulatory disease (each of which were major causes of death); there was no consistent relationship between rates of drinking and rates of death from colorectal or breast cancer, as we now should expect.  So the evidence fits together – drinking alcohol might ever so slightly increase the risk of dying from aero-digestive or liver cancer, that’s all.

Finally, it is worth noting that there is one clear way in which drinking alcohol (at least to non-alcoholic levels) increases your chance of getting cancer, and that is through its effect on living longer.  For most cancers, age is the dominant ’cause’ (e.g. half of all colorectal cancers occur in people aged over 70 years old, half of breast cancers are for women aged over 62).  Drinkers live longer, largely due to reduced levels of heart disease (also diabetes, and dementia).  Perhaps it’s also due to drinkers being more social or some other beneficial behaviours – but whatever the mechanisms, drinkers live longer and will therefore will survive long enough to get more cancer – because everyone has to die from something and the incidence of the vast majority of cancers increases substantially with age.  This fact alone is enough to produce an association, but not a direct causal one, between drinking and cancer.


Thanks to these people for helping improve my earlier drafts:

Dr Nick Danenberg, Ehrenberg-Bass Institute for Marketing Science, University of South Australia.

Ian Olver, Professor of Translational Cancer Research, Director Sansom Institute for Health Research, University of South Australia.

Philippa Martyr, Communications and Research Officer, North Metropolitan Health Service Mental Health; Adjunct Senior Research Fellow, Psychiatry and Clinical Neurosciences, University of Western Australia.

Wiemer Snijders, consultant, The Commercial Works, Netherlands.

Malcolm Wright, Professor of Marketing, Massey University, New Zealand.

Copies were emailed to Prof Jennie Connor at her Otago University email address on 8th and 24th of August, inviting her to correct any errors or omissions.  She has not yet replied.



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Gou, Xie, Yang, Liu, Zhang, Li, and He (2013) “Alcohol Consumption and Breast Cancer Survival: A Meta- analysis of Cohort Studies”, in Asian Pacific Journal of Cancer Prevention, Vol 14, No 8, pages 4785-4790. DOI:http://dx.doi.org/10.7314/APJCP.2013.14.8.4785

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Misleading alcohol cancer statistics

UK Cancer Research’s blog published a post saying that the public didn’t know much about the cancer risks of drinking alcohol.  They reached this conclusion by surveying people on the risks of individual cancers, for example, 80% of people said they thought alcohol increased the risk of liver cancer (UKCR gave them good marks for this but didn’t class this as important because almost no one gets alcohol induced liver cancer (a mere 400 cases a year in the UK)).  Whereas only 18% of people linked alcohol to breast cancer (when it’s supposed to cause 3,200 cases a year).

UKCR also said that people weren’t aware of the UK’s drinking guidelines and concluded that more needed to be done educating the public on the cancer risks of alcohol (a not so subtle call for more donations?).

I posted this comment in reply:

Telling people about estimated risks of drinking for individual cancers is likely to confuse people.  For them to then calculate their own risk they need to also know their risk of being afflicted with that individual cancer.

It would be better to instead tell people of the modest risk of being diagnosed with any cancer if they drink heavily (eg Allen 2009), yet this would also be misleading because many cancer diagnoses (eg breast, prostate) are false or for benign/indolent cancers.  So it would be more correct to tell them how much drinking might increase their chance of dying from a cancer (eg Gou et al 2013 which shows no risk for breast cancer death), or better yet dying from any cancer (eg Jin et al 2013).  But this would still be misleading because cancer is only one cause of death (and not so such a risk for younger people).

So it would be more responsible to tell the public about the evidence on drinking and life expectancy, and on their chances of ‘ageing successfully’ (without the impairment of chronic diseases like diabetes and dementia).  Understandably, this is what most people want to know.  The evidence here is that regular drinking of alcohol has a positive, that’s not negative, association with life expectancy (eg Doll et al 2005, Di Castelnuovo 2006) and disease-free ageing (eg Sun et al 2011), up to levels of daily alcohol consumption far higher than the current UK guidelines.  And, as one important part of a small suite of healthy behaviours that, in combination, have a dramatic association with disease-free survival (Khaw et al 2008, Ford et al 2011).

To not tell the public this is misleading.  But to instead confuse them with far less important statistics about individual cancers, while well meaning, is not responsible.


PS Non-alcoholic alcohol drinkers live longer than non-drinkers, and are less likely to die from heart disease.  Logically then they should be more likely to die from cancer simply because everyone has to die from something.

For a comprehensive analysis of alcohol and health research see Tony Edwards’ excellent book.

This article was not funded, commissioned or paid for by anyone.


Allen et al 2009 in Journal of the National Cancer Institute – a prospective cohort study of 1.2 million UK women (“the Million Women Study”).  Results: Compared to very light drinkers (less than 2 drinks a week) women drinking up to 3 times as much had 2% increase of cancer diagnosis, women drinking up to 7 times as much had a 5% increase in relative risk, and the heaviest drinking 5% of women had a 15% increase in relative risk of cancer diagnosis.  Though this result is largely due to breast cancer diagnoses (and most of these cases are not deadly, many are benign).  Other interesting findings include no link to liver cancer for wine drinkers.  No link to oral/throat cancer for non-smokers who drink.  And reductions in risk for some cancers (such as Non-Hodgkin lymphoma among the heaviest two levels of drinking).

Gou et al 2013 in Asian Pacific Journal of Cancer Prevention, Vol 14 – meta analysis of 25 cohort studies across nine countries.  Results: no association between alcohol consumption (pre and post diagnosis) and breast cancer mortality, nor with breast cancer recurrence after treatment.

Jin et al (2012) in Annals of Oncology, 24: 807-816 – a meta-analysis of 18 cohort studies examining alcohol consumption and risk of dying from any cancer.  The data included 48,000 deaths from cancer in the studies.  Results: A j-shaped relationship between drinking and cancer mortality was found.  Light and moderate drinkers either had less risk, or no elevated risk compared with non/occasional drinkers.  Overall drinkers (at any level) had a very small (5%) increased risk of dying from cancer, compared to non drinkers.  There was a tiny (4%) elevation in risk at around (claimed) consumption of 30g per day, while heavy consumption (more than 50g a day) was associated with a modest 30% higher risk.

Khaw et al (2008) in PloS Med, 5(1):12 – a prospective study of 20,000 people aged 45-79 in the UK examining four healthy behaviours (non-smoking, exercise, drinking, eating fruit and veg) and mortality risk.  Conclusions: Four health behaviours combined predict a 4-fold difference in total mortality in men and women, with an estimated impact equivalent to 14 y in chronological age.  Several other studies of combinations of healthy behaviours show very similar results.

Klatsky et al (2015) in The Permanente Journal, Spring 2015, Vol.19 No.2 – cohort study of 125,000 people over almost 30 years.  Results: compared to lifelong abstainers daily drinkers were 10-20% more likely to be diagnosed with cancer, no results were reported for lighter, less frequent drinkers.



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The Enlightenment can’t be stopped

Once upon a time the people who opposed freedom of speech, votes/rights for women, and the enlightenment in general were the rich and powerful. Particularly church leaders. In spite of their immense power and resources it was an argument that they would progressively lose.

Today, Islamist extremists like Boko Harem are the ones trying to wind the clock back on enlightened values. They will lose just like the Popes and Kings of the past.

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Ideology does make people do bad things

The Secular Party of Australia have called this week’s Martin Place hostage taking an act of Islamic terrorism. A number of their followers on Facebook, who presumably are normally happy for the Secular Party to point out the problems caused by religious belief, are this time uncomfortable with saying that religion was a motivation for this crime. They argue that he was a mentally ill person and that this was the cause.

Now, of course most Muslims are peaceful people. And disapprove strongly about this crime incident. However the same can be said for most people who suffer mental illness. Most people who suffer from even very serious mental illness do not approve of ISIS, nor hate the Australian govt for fighting against the attempt by ISIS to forcibly take over Iraq.

So even if mental illness played a role here it did so along with religious belief. They are undoubtedly a dangerous combination. And sadly probably have a tendency to occur together.

Furthermore, in defence of the Secular Party’s comment, the hostage taker himself said his actions were motivated by Islam. It seems presumptuous of people to ignore this, to ignore the consistency with his behaviours, but to assume mental illness.

If he had a Mohawk haircut and maintained a right-wing blog then no one would doubt that his ideology played a crucial role (even if he was mentally ill) in his chosen actions. What he instead did was make trembling hostages hold up a flag that said “Allah is the one true God and Mohammad is his messenger” and so on. To argue that this has nothing to do with religious ideology seems wrong or disingenuous.

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