You have to pick a number and defend it!

No. http://meaningness.com/meta... and the comments provide a nice illustration of why that's not the case.

Picking probabilities and defending them is not the only paradigm for decision making. The fact that you can't think of other paradigms doesn't mean that they don't exist.

Nassim Taleb books also provide good explanations.

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Whats the risk of global pandemic/ supervolcano / tsunaumi / nuclear war / micro black hole / rogue nanobots / Bee population failure / alien invasion / asteroid impact? You're not sure? Well, we should act! Its unreasonable to require p>0.99 to become serious about preventing the risk...

You can't use unknowability to fuel your pet risk aversion, because all manner of projects can be conjured into being on the same invocation of unknown risk. You have to pick a number and defend it!

Sigh. The best way to increase resilience is wealth.

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This, I think, is essentially the foundation of Machiavellian ethics, and the same sort of reasoning used by Lee Kuan Yew in the early years of Singapore's independence. 

We were war-torn following WW2 and the Japanese Occupation, and reparations were given priority over political freedoms. We were a broken country, and I think we're doing quite alright now. 

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 Fair point, but the risk on that is a lot lower, right?

And even 6C' is mitigable. And may even be cheaper to mitigate than avoid.

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To Christian,

 I meant "are you SURE?" in the sense of "what's your source?" Nearly all the studies I've seen don't have much costs at up to 2C. Relax, I'm not demanding P>0.99 for those projections...

I find your objection bizaare. Are you saying that tail risk is so huge AND unknowable (no uncertain) that we must avoid the scenario at all costs? We're not talking a 50% uptick in Hurricanes here - that's small change - you seem to be predicting 1000%+ increases in damage and frequency which is what you'd need to build an economic case for action.

Note that we have no strong evidence for any change SO FAR.

If so, I must ask for sources for these massive tail risks. I've never seen anyone suggest that for extreme weather phenomenon from climate change of a few degrees.

I just think you are going very far beyond the mainstream models and even further from the empirical evidence.  

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"Are you SURE" is a bad question to ask when it comes to forcasting those events. It's not about being sure. I don't claim p>0.99 for that claim.

It's irresponsible to require p>0.99 for such a claim to become serious about preventing the risk.The Dutch have the advantage of not suffering any hurricanes or similar weather events. That makes there fate very different than the fate of costal cities in the US.The danger isn't a gradual increase in see level but that extreme events get more likely and more painful with increased levels.That's also why you can't calculate the opportunity cost in an effective way. In complex system where you don't know the output well enough it makes sense to focus on increasing resistence instead of maxizing a flawed utility function. 

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 Yes, the whole God and Pre-crime problem. In the 2013 remake, Satan (played by Tom Cruise) finds himself accused of a rebellion he has not yet committed. 

But the intial assetion by Robin did seem curious.

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 Are you SURE, Christian? IIRC, most projections up to 2C'  are beneficial or neutral for humanity, mostly via agricultural production gains via increased precipitation, growing season, and CO2 fertilisation, and lower cold deaths...

Coastal city flooding is small change at the level of resources required for abatement strategies. Remember, 1/3rd of the netherlands is under water NOW. Doesn't seem to bother the Dutch.

You need to sketch out the abatement vs. mitigation costs for each 'C, use the delta for opportunity cost, and discount appropriately to find the best path. I've never seen this done by the Greens....

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Ah, yes, Peter Singer. What is it about moral systems that invoke obligations to non-existent entities being so popular amoungst the bien pensant? I ran across this is justification in the Stern report for their ridiculous 0.1% discount rate decisions and it stuck badly in the craw there.

Future entity welfare only has ethical claims insofar as current, real entities value such welfare. If you allow non-existent things to make ethical claims on their own behalf, all sorts of crazy can be conjured into being.

I predict that the great numbers of our vastly wealthy descendents would prefer their ancestors to have enjoyed their sadly inferior time on earth. They would want us to kick back, have a beer, and invent workable jet packs and warp drive. They are very specific about the jet packs.

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He doesn't believe wealth has a significant effect on happiness.

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Throughout history a lot of societies did go down because they didn't manage to solve it's problems. Take the Maya. Their civilisation perished long before their calendar ended. 

If you don't have enough food the result isn't simple that children starve.If arable land becomes unarable and you start using the land of other people, violent conflicts ensure.If problem aren't solved at the level of the society you get political violence.Most individuals are also dependent on a lot of public infrastructure. If my supermarket wouldn't have food for a month I would have real problems as I grow none of my own food.Actually in those developing countries women are stopping having 7 children. 30 years ago 23 countries had 7 or more children per woman. Today only Niger has. In 2010 Niger had 7.06 children per woman. In 2011 7.01 children per woman. We don't have data yet for 2012 and maybe Niger got below the 7 mark in the last year. 

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srdimond: I don't believe in Bright Line Morality.

But if anything is immoral, making children suffer and die is surely among it?

Or the other way around: If making children suffer and die is not immoral, then surely we have no reason to condemn Marc Dutroux either?

As for the line, if I were to aggress against your children, would you rather I make them suffer and die, or would you rather I make them omit college?

Nancy: Yes, male aggression can be a problem.

But it is women's bodies who create the children.

You could kill 99% of all men, and still have enough sperm to create as many children as you want.

With the exception of rape, all children are a function of women voluntarily accepting sperm inside their bodies.

Peter: In order to transfer wealth to the future, you need to have wealth.

I admit that, but if you don't have wealth, having kids harms them because it likely makes them suffer.

If I can't afford dog food, I don't buy or breed a dog.

As for the means of transfer, money and property rights exist even in poor countries.

Even in totalitarian failed states, people pocket grains of gold and so on.

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Malnourished children are not a function of a lack of  resources.Malnourished children are a function of a lack of personal responsibility in reproductive choices.Sheesh! What simple-minded thinking to appear in Comments to an economist's blog! If impoverished people could be magically convinced to eschew offspring, you imagine the immediate effects and the demographic effects would be benign? And from where derives the conceit that "malnutrition" is the Bright Line Moral Consideration. Why not condemn people who can't afford to send their children to college to genetic extinction?.

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In reply to Margin:

"Even for poor people there are ways to transfer wealth to the future, robust enough to predict whether or not they can feed more children."

Give examples.

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Might men in the third world be some fraction of the problem?

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I was reading it more like values dissonance. They'd value preserving resources, and, when they bother to think about it, they'd consider us behaving immorally by wasting them. This is similar to how we value freedom, and when we bother to think about it, we consider historical slave-holding societies to be immoral.

I don't think driving cars in circles is a very common leisure activity. Most people just watch other people drive cars in circles, which is a less wasteful. I think most of the waste is actually from the people watching it who could be doing something more productive. Of course, when people do spend more time being productive, they tend to just waste all the money they make on leisure. Few people try to invest their money indefinitely to help people in the future.

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