

Ask Hacker News: What is the % chance of cataclysmic climate change? - rms
http://www.nature.com/ngeo/journal/v2/n12/abs/ngeo689.html

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bdfh42
Cataclysmic event? An incoming asteroid or the Yellowstone super volcano
erupting - both cataclysmic I suppose with a finite chance of occurring. Both
of these would probably have a chilling effect over the short term (couple of
hundred thousand years).

Runaway warming following some massive release (from somewhere) of a
greenhouse gas - possible one supposes but it does not look as if anything
like that has happened during the last few million years.

The most likely medium term scenario based upon the rather limited historical
climate data we have is that we will slowly move into another ice age. Now
that will be cataclysmic for folks living in the Northern temperate zones
where most of the current world economic activity takes place.

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rms
Cataclysmic is pretty unlikely. Do you think there is 1%+ chance of some major
coastal cities becoming uninhabitable or requiring significant engineering to
hold back the rising sea?

~~~
bdfh42
Interesting question and I suspect difficult to get a sensible answer to. I am
assuming that you expect the 20th Century warming period to continue to raise
Northern hemisphere temperatures to the levels experienced around 1,000 years
ago. Certainly we know that Greenland had a lot less ice then - although we do
not know where that water was. I am not sure if we have any information from
Northern Canada or Asia. Regretfully I have not heard about any useful data
from the South. Was the sea level higher a thousand years ago? Even
extrapolating from coastal site evidence might not help as many land masses
were still (and are still) rising gently following the last ice age.

There is not a lot of evidence that sea levels are rising substantially at the
moment - you had best ask an oceanographer - I would stick with the science
rather than ask a "climatologist".

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rms
The argument against global warming seems to be that there is a lot of
uncertainty. The models really could be wrong.

What is your prior probability for the formal scientific opinion on climate
change being correct?
[http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_c...](http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change)
I choose 95%.

What percent chance do you think there is of cataclysmic global warming, human
caused or otherwise? I can't pick an exact number, but it is certainly above
0+ and it seems like a bad enough scenario that it is worth doing something to
try and stop it if we can. Note that I don't think this type of analysis is
very meaningful quantitatively, but it can reveal why people think the way
they do. I really don't understand the contrarian perspective on global
warming and I would like to hear how you justify your probabilities.

~~~
hga
Well, one of the issues is magnitude: do we get, naturally or unnaturally,
temperatures back to the level of the Medieval Warm Period or do we get a
"cataclysm" (or do we get the next Ice Age, we _are_ overdue one, and the same
general group of people and some of the same people were warning of that
before the '80s).

"Worth doing something" is nice and fine, but that "something" really needs to
be connected to the probability of the risk. The extreme warmists want us to
essentially spend all the world's disposable wealth on something that has at
best a _very_ shaky scientific foundation (cataclysm). It would be a real pity
if we did that and it turned out we were entering the next Ice Age instead, or
needed the money for some other greater threat instead (e.g. one of the ones
mentioned in this discussion, like a megacaldera cutting lose). A maxim of
warfare is that the side that tends to win in a battle is the one that is the
last to commit its reserves. We _really_ need to keep some reserves.

In the HN discussion in which you posted a pointer to this discussion I
referred to Bjørn Lomborg, "The Skeptical Environmentalist". Back before the
release of the CRUtape Letters he believed moderate AGW was happening, but he
advocates moderate local expenditures to deal with that (moderate at least
when compared to the "take over the world's economy" proposals of the extreme
warmists), and that we spend some serious money on targeted interventions that
will clearly help a lot of people (e.g. as I vaguely recall one involves
addressing a common vitamin deficiency).

Unless a threat is truly cataclysmic it's a mistake to focus on it to the
exclusion of all else, and the extreme warmists are just one example of an
advocacy group that thinks they've found the _one_ problem we're facing.

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revorad
In Global Catastrophic Risks [1], many of the risks considered, including
unfriendly AI and nuclear war, are argued to have a higher probability of
causing catastrophe than climate change.

[1] <http://www.global-catastrophic-risks.com/>

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jeffcoat
This looks like a job for ... Prediction Markets!

As in, seriously: has such a thing already been set up?

