Note: Please see this post of mine for more on the project, my sources, and potential sources for bias.

I have written a couple of blog posts on my understanding of climate forecasting, climate change, and the Anthropogenic Global Warming (AGW) hypothesis (here and here). I also laid down the sources I was using to inform myself here.

I think one question that a number of readers may have had is: given my lack of knowledge (and unwillingness to undertake extensive study) of the subject, why am I investigating it at all, rather than relying on the expert consensus, as documented by the IPCC that, even if we're not sure is correct, is still the best bet humanity has for getting things right? I intend to elaborate on the reasons for taking a closer look at the matter, while still refraining from making the study of atmospheric science a full-time goal, in a future post.

Right now, I'm curious to hear how you formed your views on climate change. In particular, I'm interested in answers to questions such as these (not necessarily answers to all of them, or even to only these questions).

  • What are your current beliefs on climate change? Specifically, would you defer to the view that greenhouse gas forcing is the main source of long-term climate change? How long-term? Would you defer to the IPCC range for climate sensitivity estimates?
  • What were your beliefs on climate change when you first came across the subject, and how did your views evolve (if at all) on further reading (if you did any)? (Obviously, your initial views wouldn't have included beliefs about terms like "greenhouse gas forcing" or "climate sensitivity").
  • What are some surprising things you learned when reading up about climate change that led you to question your beliefs (regardless of whether you changed them)? For instance, perhaps reading about Climategate caused you to critically examine your deference to expert consensus on the issue, but you eventually concluded that the expert consensus was still right.
  • If you read my recent posts linked above, did the posts contain information that was new to you? Did any of this information surprise you? Do you think it's valuable to carry out this sort of exercise in order to better understand the climate change debate?


New Comment
145 comments, sorted by Click to highlight new comments since: Today at 6:17 PM
Some comments are truncated due to high volume. (⌘F to expand all)Change truncation settings

Based on my appreciation of the scientific method and my research into the weaknesses of models and experts, I take the median IPCC estimate as correct, but assume the uncertainties are greater than they claim. This is somewhat scary, as uncertainties cut in both directions, and moderate climate change is something we can cope with, but extreme climate change is very much worse.

I basically hold the same position.

I am highly confident that anthropogenic warming is occurring, with some concern that institutional pressures will tend to exaggerate the amplitude of warming predictions. As an aspiring geologist (master's level, for now), I'm unusually well-informed on the issue; I have spent considerable time discussing climate changes with geoscientists of various specialties (in particular, chemical oceanography, isotopic geochemistry, paleobotany, regional weather forecasting, and geobiology), and I have the education to read the primary literature comfortably. Working in the same labs as the experts has been especially helpful, since they have universally been happy to discuss complexities and uncertainties as I encounter them in my own studies. It's worth pointing out that my own work is not directly related to modern climate change, so my own 'insider status' is questionable.

I was less confident when I first entered the sciences than I am now, although I didn't ever qualify as a 'climate skeptic' except insofar as I was a skeptic with thoughts about the climate. The increase in confidence has been ongoing, with many causes- I recall a particularly visceral shift in perspective came whe... (read more)


I don't have any.

I know next to nothing about climatology and I have no way of determining which experts are trustworthy. I don't think that trying to form an opinion on it would be a worthwhile use of my time: I have no need for one, and it wouldn't be a very useful source of data either way -- I don't think there are any meta-level lessons I could learn from its truth or falsity. Developing a belief would create a very significant risk of forcing me into one of two camps, with decidedly negative consequences for me either way, whereas if I don't develop one, that only makes me elthedish to the people who believe that everyone ought to have an opinion on it, and I don't mind that at all.


In many issues like this, my opinion is formed automatically without my conscious will or any kind of deliberate reasoning. I don't have opinions on highly technical issues I don't really care about, but on highly publicized issues like global warming it's hard for me not to develop any kind of preference to one direction or another. I had a certain feeling about global warming before I even knew enough about all the relevant facts and the science behind it, and this feeling was probably formed using very straightforward subconscious heuristics. So the question then is not "should I form an opinion on this", but rather "should I trust my gut feeling enough to call it an opinion and make it a small part of my identity" or "should I investigate this more to get a better feeling on the subject".

But this is just me, I'm not sure how other people's minds work. So do you mean you don't have even a slight preference to either direction? Or do you mean that this preference is not on such a firm ground that you should pay attention to it?

I don't have even a slight preference to either direction, but this is the result of a deliberate attempt at deprogramming, noticing beliefs that I can't back up and that appear to originate in downstream-from-politics status concerns and trying to remove them: I grew up with a vague sense that 'climate deniers' were stupid and inferior, but 1) vague senses are worse than zero information, 2) I grew up with other vague senses that turned out to be totally wrong, 3) the vague senses I grew up with are mostly historically recent enough [this one included, of course] that I can't even use Burke to justify taking them as priors without being able to argue any side of them. My original opinion did form automatically without my conscious will or any kind of deliberate reasoning; I had to notice that I didn't know the first thing about the issue and stop having opinions about it. I decided a few years ago to root out and reject received status/authority-concerns masquerading as knowledge, to stop having opinions about factual matters that I don't know enough about to form an opinion on. I still have a vague emotional sense that AGW is more likely than its absence, but I try not to pay attention to that, and it certainly doesn't qualify as a belief or a view: it's a stupid thing that my brain does when I don't tell it not to, since completely deprogramming is a lot harder than just removing beliefs.
Your beliefs in anthropogenic global warming affect your political position, and if you live in a democratic country, your political position affect government policy: you can vote, you can campaign with various level of commitment, you can run for office. Even if you choose to do no such thing, you are still making a political decision. And by the way, what do you mean by "I don't have even a slight preference to either direction"? It's not like it is a binary question where you can assume a 50% prior probability. You must be necessarily using a non-trivial prior. Then why are you deliberately ignoring evidence that could be used to update?
What's your opinion on the situation in Mali? -------------------------------------------------------------------------------- What I mean to imply by "I don't even have a slight preference to either direction" is not that I assume a 50% prior probability to each side; it's that I don't assume a prior probability. Assuming one would be uninformative noise, since I don't know enough about it to have an opinion -- and it would be both harmful and irresponsible. Harmful since it would commit me to a prior for something that I don't want to have any priors about -- once I write down a percentage, I've committed to that percentage, and I'll be more likely to update based on it, even though it has next to nothing behind it and I don't want to go anywhere near it -- and irresponsible because, if I do it in public, it'll give other people something to update on, even though it's little better than getting a percentage out of a random number generator. I'm deliberately ignoring evidence that could be used to update because I don't think that I'm obligated to have an opinion on literally everything in the world. My time is better spent elsewhere. And I'm deliberately ignoring the non-trivial priors I would base a probability estimate on if I ended up in an absurd counterfactual world where I absolutely had to give one because they're a product of the environment in which I was raised, they're not old enough to be justified in the Burkean sense, and I don't think that the processes by which those environmental opinions are formed have anything more than the most tenuous connection to the actual truth, whatever it is. Background reading:
Democracy has the wonderful property that it obeys the Central Limit Theorem. Each person concentrating on the areas they know well and care about produces an overall bell curve that makes a fair bit of sense, even if no individual voter sees the big picture very well.
Whaaaaaat? 8-0
In a very handwavey sense. Voters are not, strictly speaking, IID. But it works out pretty similarly. I find that politically active folks(whether seriously or casually) mostly tend to care passionately about certain issues, but the actual election results are vastly smoother.
I don't think this comparison works at all. Not only the voters are not IID, but the actual election results are a discrete outcome and there is nothing "vastly smoother" about them. The political process is full of threshold functions.
Oh, certainly. But the overall motion is much less than one might think. A real blowout defeat of a party in the US is getting 45% of the vote to your opponent's 54%. Most countries are similar, if with more parties. The government swings, but voters as a whole don't do so too heavily.
So you are saying that the political views of populations are largely stable. Sure. But what does it have to with either democracy or the Central Limit Theorem?
Not just stable. Moderate, rarely obsessed with single issues, and in retrospect they're usually pretty good at making wise decisions on the broad strokes(even if they're bad at micropolicy - which makes sense, because so few people care about it). It's for the same reasons as the CLT, which is why I named it - the distinguishing characteristics and individual madnesses of voters cancel each other out, and you're left with a signal whose characteristics are defined by broad statistical characteristics, and not the quirks of a small group.

What are your current beliefs on climate change? Specifically, would you defer to the view that greenhouse gas forcing is the main source of long-term climate change? How long-term? Would you defer to the IPCC range for climate sensitivity estimates?

Based on asking UCSD scientists when I've met them at parties, I'd parrot them and say human emissions are maybe about 1/2 of the source of long term climate change. I would not defer to the IPCC or to anybody without giving them careful reads. The issue is too politicized to trust anyone merely because of fancy or scientific sounding titles.

What were your beliefs on climate change when you first came across the subject, and how did your views evolve (if at all) on further reading (if you did any)? (Obviously, your initial views wouldn't have included beliefs about terms like "greenhouse gas forcing" or "climate sensitivity").

When I first heard of global warming I thought it was ludicrous because I could remember a number of years ago reading about the coming ice age and all the evidence for that. The idea that we should bring CO2 emissions to a halt is ludicrous to me even in the face of real climate cha... (read more)

I'd say abandoning entire coastal regions is pretty damn catastrophic, even if it's an orderly retreat and nobody drowns. That's still billions (trillions?) of dollars worth of real estate vanishing under the waves, not to mention the immense cultural loss. Then again, median estimates for sea level rise never end up more than about a metre. If this simulation is to be believed, it won't encroach on coastlines that much. How expensive would it be to build giant levee systems to keep the water out of Bangladesh, like the Netherlands?
The real estate itself: as much ocean-front real estate is created by sea-level rise as is destroyed, approximately. So at this point, it is only the improvements upon the real estate which are lost. With sea level creeping slowly up, these losses should be minimal. Structures have various economically useful lifetimes ranging from years to many decades depending on the structure. And it should be noted that sea levels have been rising for longer than human civilization has existed. Loss of real estate and improvements because of natural shifts in land vs water levels is nothing new.
There isn't a substantial change in the amount of ocean-front real estate, but there is a substantial change in the total amount of real estate. Super-crude model: you have a square island of side 1 unit; rising sea level reduces the side by 0.01 units of length, which by coincidence is also how near the sea something needs to be to be "ocean-front". Before, the total amount of land is 1 unit and the total amount of sea-front land is 0.0396 units. After, the total amount of land is 0.9801 units and the total amount of sea-front land is 0.0392 units. So the total amount has gone down by ~2x as much relatively, and by ~50x as much in absolute terms.
Cool idea using numbers! From wikipedia we see that a 1% decrease in above sea level land area happens with about a 10 m sea level rise. In your example above you work with a 2% decrease in area, so you are developing numbers associated with a 20 m rise in sea level. Predictions are for 0.2 to 0.6 m sea level rise in 100 years. This causes a 0.02% to 0.06% reduction in land area, associated with a 0.01% to 0.03% reduction in coastline.
So, pulling some numbers out of my rear end, let's suppose that 5% of the world's GDP comes from "land-based" activities in some sense, and let's suppose that losing coastal land is 10% as bad as losing average land (e.g. because most farms aren't right on the coast or near enough it to be badly affected by this change). Then losing 0.04% of the land would reduce "gross world product" by 0.05 x 0.1 x 0.0004 = 0.000002 = 2 x 10^-6 of its value, or about 2 x 10^-6 x $10^14 ~= $0.2B annually. That's a lot of money but seems likely to be a lot smaller than, e.g., the impact on agriculture of temperature changes, or the cost of serious mitigation efforts. (I'd guess that the costs would be relatively much greater for poorer countries, more of whose economic activity is agricultural.)
The economic impact depends mostly on the loss of homes and other buildings, not farmland. A good fraction of the world's wealth is tied up in buildings, and those tend to be concentrated near coastlines. But levees can be built in many areas, and some buildings in other areas might be worth putting on stilts. So the costs of levees, stilts, and abandoned structures are what you most need to examine, I think, to assess the economic cost of sea-level rise.
What, that's close to nothing! $0.03 per person per year. And the effect is even smaller than that. Higher sea level pushes the atmosphere up as well, which means we are improving land at higher elevations by having more air on it. This will reduce the net loss of valuable land.
If the most effective charities can save a life for $2k, that's enough to save 100k lives/year. But of course there are plenty of other things it's small in comparison to; I mentioned a couple of relevant ones. I think this is likely to be a much smaller effect. The great majority of land is no more than ~1000m above sea level.
The most effective charities can save a life for $2k today (where by “today” I mean ‘a couple years ago’) because there's lots of low-hanging fruit, but I doubt this will continue to apply much longer.
Higher sea level from ice falling into the water results in the air being lowered since the ice became denser in the process.
Clever, yes. However, it also comes with the opening up of relatively low lands that were previously covered by ice. AND, I have read that a significant fraction of sea level rise is due to the ocean water expanding since slightly warmer water is not as dense as slightly cooler water, which would serve to push the atmosphere up. I think if you totted it all up, you would see a small loss of value in the land area available, but much smaller loss in value than in land area lost. That is, the remaining land would have higher value per hectare on average for a few reasons.
The air is warming too, and the expansion of the air will make it less dense, which utterly swamps the effect from the expansion of the water. Really? I see that the other way around. Beaches are valuable, and it will take a lot of time or money to make them at their new sites. Estuaries provide a lot of ecological services and are basically flat. Having them be at the wrong depth will screw up those services. Many cities (concentrated value) are right down on the water, and it will be muy expensive to save them and enough of their outlying areas that they remain convenient (which was a large part of why they were cities in the first place).
I am sorry, I don't see anything like these numbers in your link.
I digitized the elevation distribution figure and took the slope right around sea level.
The link shows (just eyeballing the plot) about 80% of the earth's land area being fairly uniformly distributed between 0 and 1000m above sea level. If we assume (a bit too simply, but it probably isn't very far off) that a 10m rise in sea level will simply turn everything between 0 and 10m above sea level into no-longer-land, that suggests about (10m/1000m)*80% ~= 0.8% of the land would go away. Doesn't seem too far out. (How bad is the oversimplification mentioned above? It's too pessimistic because some land below sea level might remain usable, as with the Netherlands. It's too optimistic because some land still above sea level might become much less usable, e.g. by turning into little islands. My guess is that both these effects are quite small and they're similar in size.)
Substantial..? Plug in the numbers for the size of the North American continent and for the expected sea level rise by 2100, for example, into your super-crude model.
I probably shouldn't have said "substantial" since what I really meant was "not cancelled out in the way mwengler describes". I don't think I can actually do the calculation without an estimate of the typical gradient of coastal land in the US (i.e., the conversion factor from sea level rise to shrinkage) but let's make a crude guess and see what happens. So, North America has an area of about 25M km^2 so our square is about 5000km on a side. Expected sea level rise by 2100 is about 0.5m (I've seen wildly inconsistent figures for this, though). Let's suppose that sea-level land has a typical gradient of 1 in 50, so that a 0.5m rise means a 25m shrinkage in the usable land. Then the total amount of land lost would be about 20000km x 25m = 20km x 25km = 500 km^2, roughly comparable to the area of San Francisco. This is probably an underestimate: North America is wigglier than our square model (so more coast relative to its area) and I suspect that actually coastal land is flatter than 1 in 50. So it's a small fraction of the total area (as of course was obvious from the outset) but personally I'd consider it a substantial loss if an area the size of San Francisco fell into the sea.
I would like to add that at any particular piece of the coast it is NOT the global ocean level rise that determines its fate. The edges of continents generally sink or rise, depending on what a particular tectonic plate is doing and what is the area's recent geological history (e.g. the Hudson Bay area is still rising having been freed from the weight of the glaciers after the last Ice Age ended, but the areas of coastal Maryland or Louisiana are geologically subsiding). There are also things like the silting up of river estuaries, rearrangement of barrier islands by hurricanes, etc. etc.
There seems to be:
I agree, sea level is rising and has been rising for 1000s of years. What lead me to say it is not rising is my recollection from reading Michael Crichton's State of Fear, published 2004. I remember his claim as something like there is no evidence of sea level rise recently. I may be misremembering it or he may have made the claim, maybe he claimed there is no evidence for off-trend sea level rise, of accelerated sea level rise. Whatever he claimed, I agree sea level is rising.
(Not saying you still believe this, but note): To the extent that was predicted at all and was not simply popular press inflation of a contrarian viewpoint, it was due to aerosol air pollution, which drastically reduced starting in the 1970s. 1) Germany has been putting a lot of effort into this. How's their economy doing, again? Seems all right. 2) Fossil fuels are inherently limited, [edit:] and[/edit] you don't need a very long term before relying on them begins to seem like a false economy. Fossil fuels as a whole may still be growing as fast as ever, but oil's growth has slowed down. Even if global warming weren't happening at all, we'd be better off getting ourselves significantly freer of oil over the next decade or two. 3) IF they don't change... well, it's not as if these are entirely independent. If we put in real efforts, we'll have a lot better standing to demand that they change. Our doing nothing has been their excuse to do nothing for nearly 20 years. 4) As you alluded, there are cheap and VERY expensive ways of mitigating CO2 release.
In a free market, so long as the interest rates are not too high, depleting fossil fuel reserves would raise fossil fuel prices decreasing fossil fuel consumption, with no need for government and/or collective action. (Arguably that's already happening; I also suspect that it's a major part of the reason of the Great Stagnation since the mid-early 1970s, especially given that people pointing it out like to measure it in terms of metrics such as energy consumption per capita.) So all we have to do is realize we're in a hole and stop digging.
That argument would apply just as well 200 years ago, right?
I'm assuming (perhaps incorrectly) that people who read this are familiar with the idea that we are approaching peak oil, and can expect it within the next 20 years, perhaps less, so they know how to appropriately fill in the blank on 'very long term', which we would have been filling in rather differently 200 years ago. If you seriously didn't know this, well, now you know the implicit part of my argument.
I can't speak for everyone who reads this, of course, but as to myself, I am familiar with the idea that we are approaching peak oil -- moreover, we have been approaching it for the last 40 years and, if anything, we seem to be farther away from it than we used to be. So, given the very consistent, I might even say systemic failures of peak oil forecasts, I have to be quite sceptical about the current one as well. 200 years ago, of course, oil was just a useless nuisance. People were concerned about coal. Notably, there is still lots and lots of coal around.
1) The prediction of peak US production was basically right on the mark. Other national predictions have been accurate too. 2) The failures of peak oil predictions have been primarily from the willingness to get to less and less accessible reserves at progressively rising monetary cost (see: dramatic increases in the price of oil) and, recently, (non-AGW) environmental and even health costs. 3) Until recently, few alternatives have been available, so whatever the consequences to getting more oil, we HAD to accept them. Electric cars were jokes. This is rapidly ceasing to be the case. 4) I am aware there are vast coal reserves. However, last I checked, no one uses coal for transportation anymore except by going through the power grid (electric trains), so I'm not sure how that actually addresses my earlier comment. Note: I am indeed falling back from my naively phrased claim in my previous post here. However, this doesn't impact the usage in the post before that.
There are things for which there still are no alternatives to fossil fuels and there will likely never be: for example, how the hell are you going to power long-haul aircraft?
Hydrocarbon fuels don't need to be fossil; there are methods you can use to convert biomass into synthetic fuel, though outside of ethanol and the odd biodiesel project synthetic fuels usually use coal as a feedstock right now. It'd be more expensive, though.
Commercial aviation is just barely economically viable today, and fuel getting much more expensive would it make all but impossible for airlines to make any net profit. But yeah, this might change in the future.
Have you seen how much of an international ticket price is taxes, etc.? Did you mean to say that airline margins are razor thin?
[citation needed]
It's pretty notorious. Airlines routinely go bankrupt and prompt articles like "The Economist explains: Why airlines make such meagre profits" army1987's point is ill-posed and makes little sense in a supply-demand framework - the more interesting question is how much ticket prices would have to rise if fuel got much more expensive, since obviously they would rise & airlines wouldn't simply stop flying entirely.
There are no issues with economic viability of commercial aviation today. Consider what would happen were it to shut down. I think you're confusing the quoted sentence and "I think airline tickets are expensive".
It is more likely that he is 'confusing' the quoted sentence and the findings from analysis of business failures (and marginal successes) in the industry in question compared with other industries and various analyses about the market forces that produce that result. This is still not quite the same thing as "commercial aviation is just barely economically viable today" but far closer than "I think airline tickets are expensive". (I agree with Lumifer that Army's conclusion does not follow. Tripling the cost of fuel would still result in a viable albeit far, far smaller commercial aviation market.)
The cost of fuel seems to account for about 20% of the cost of the ticket on a US domestic flight (source). Given that international flights have higher fees, I expect the fuel cost percentage to be even smaller for them. For example I took a look at a New York - London return economy ticket which costs about $1050 now. Out of that amount $250 are government taxes and fees (NOT including the sales tax).
I don't; otherwise I just wouldn't buy them. Where did you get that from my comment anyway? But what I think is irrelevant. It's the aggregate market demand that counts.
Let's look at the aggregate market demand. The annual passenger total is about 3 billion people. Doesn't look "barely economically viable" to me. At all.
And yet airlines lost money for most of the past decade. So these 3 billion passengers aren't paying them that much. (And I don't think it just doesn't occur to airlines to raise prices; presumably they wouldn't get as many passengers if they did.) Even more recently, it looks like the average net profit per passenger (average, not marginal) is of the order of $5.
From the link in the parent post, about $600 billion. Peanuts, I know. From the link in the parent post, net profit for the last five years: * 2010: $17.3 billion * 2011: $7.5 billion * 2012: $6.1 billion * 2013 (est): $10.6 billion * 2014 (fcast): $18.0 billion
Which divided by 3 billion would be $5.77/passenger in 2010, $2.50/passenger in 2011, $2.03/passenger in 2012, $3.53/passenger in 2013, and $6/passenger in 2014. What did you think I meant by “of the order of $5”?
Yes, we agree on the numbers, we're just throwing connotations at each other :-) $5 is a small number so you're pointing to this. $somebillions is a large number and I'm pointing to that. I am still pretty sure commercial aviation is perfectly viable economically, it's just that certain peculiarities of the business make it hard to make lots of money in it. However it's not going anywhere and, say, doubling the fuel prices will not make it go away either.
That has more to do with the fact that air travel is commoditized than the price of inputs.
So, um, are you saying there never will be anything with the energy density as good or better than jet fuel..? That's probably true for the next 10-20 years, but "never" is an awfully audacious claim.
Believe it or not, this was seriously considered during the Cold War. Some manned prototypes even flew with their reactors going (albeit not to power the plane), though the problem of shielding wasn't adequately solved before progress in ICBMs made nuclear-powered bombers pointless. Then there's Project Pluto, though that would have been less a conventional aircraft and more a terrifying drone bomber built around an unshielded nuclear ramjet the size of a bus:
You are trying too hard :-) Your first point says that the predictions were correct and then the second point tries to explain the failures :-D Re (2) and (3) peak oil people didn't claim that oil will become too expensive or inconvenient to extract -- the claim was that the oil will run out, full stop. Re (4) we were talking about fossil fuels in general, not only about what's used for transportation. But in any case, you can convert coal and natural gas to liquid fuel. The technology is well-known.
Paragraph 1: You said it was completely systematically wrong. I pointed out that it wasn't systematically wrong and then explained the cases where it was. Paragraph 2: Peak oil is not an ABRUPT EXHAUSTION, but the time of greatest production. Paragraph 3: Go back. This was in response to my claim specifically about oil.
Where do you think the energy to charge electric cars is coming from?
Elven magic.

I think that the Earth will get warmer in the same way that I think exercise is good for longevity. I'm not competent to evaluate the arguments or even evaluate the people who evaluate the arguments, but there seems to be enough evidence from different sources to make me reasonably confident.

I have no idea what climate change's impact will be on people. Are current global temperatures optimized for human welfare? Probably not. Will making temperatures warmer be an overall gain or loss to human welfare? I have no clue. Is the cheapest way to avoid harms reducing CO2 emissions, or building levees, or moving everyone 10 miles inland, or putting mirrors in the stratosphere, or something else? Again, no clue.

I am encouraged that people are taking the welfare of humans hundreds of years in the future seriously. I am discouraged that the discussion on climate change is dominated by if it real, not what will its effects be and how can we optimize the upside and minimize the downside.

Are current global temperatures optimized for human welfare?

It does seem extremely unlikely that global temperatures are optimized for human welfare, but not as hard to believe that human welfare is optimized for current global temperatures.

Why? Most of human evolution happened when it was colder than today, whereas much of human agricultural civilization happened when it was warmer (1, 2).
Is there a reason why you're limiting yourself to evolutionary innovations that occurred after human speciation? Most of our thermoregulation techniques are at least as old as the Triassic, which was much warmer. Conversely, less elaborate adaptations can happen very quickly. The pale skin of Europeans seems to have originated after the end of the last ice age, for example. It's also worth pointing out that our species seems to have been basically regional until about 60,000 years ago. So even if we limit ourselves to the last 200,000 years of adaptation, we should calibrate those expectations based on the African regional temperatures rather than a global average. Humans living in New England today may well be experiencing colder temperatures than their ice age ancestors.
It's likely that a disproportionate account of optimization of human welfare has occurred in the last few centuries. Moreover people are mobile and the variation in temperatures over the surface of the earth is greater than over a few thousand years. So humans are likely to have optimized their location to approximately optimize their welfare.
This is VERY technology-dependent. Only a hundred years ago southern Florida was considered not a fit place for people to live in, being, basically, a swamp infested by alligators and malaria mosquitoes.
Population shifts in the last century have been ludicrously massive, with no real ill effect. If there's climatological reason, we can do so again.
If the shifts cost a few billion dollars, that likely would hard to measure. So I guess the question is what rises to "real" ill effects, and what is "ludicrously massive". I think most people would consider the shift in population from Africa to America during the seventeenth and eighteenth century to have involved significant real ill effect, and that involved only a small fraction of the global population.
The ill effect had very little to do with the shipping, and a whole lot to do with what was done with the people who were shipped. If the sugar plantations had been in Sierra Leone, it wouldn't have been any more humane.
A lot of systems are optimized for current temperatures, including: ecosystems, agriculture, the economy, coastal habitations, etc. - and degradation of those system is bad for human welfare; they would eventually be re-balanced, but at a cost. (Yes this is a fully general argument in favor of the climatic status quo)
This actually looks like a fully general argument if favor of any status quo.
Are you saying my argument proves too much? I agree that it's an argument that can be used in favor of status quo in a lot of situations (it's similar to Chesterton's Fence), but it won't apply as strongly; the argument mostly requires that changing the status quo disrupts system that: * Impact human welfare a lot, and * Are slow to re-stabilize ... so a good argument can be made that climate does that, but the effect is less strong for national politics, and even less strong for things like corporate policies, roles inside a family, etc.
I am saying its overly broad. Why not? Example: Russia. The collapse of the USSR both impacted human welfare a lot and the society was slow to re-stablize. Or how about independence wars or revolutions in general? The problem with your argument in meta terms is that it discounts the long-term utility too much in comparison with the short-term utility.
You mean, those things that almost always increase human misery and fail to accomplish their objectives? Aside from the Americans, whose revolution was fundamentally very conservative(it was based on the rights of Englishmen as understood in the time of their grandfathers more than anything), revolutions are notoriously bad ideas.
Those things which move history forward in bloody spurts and zigzags, yes.
It's an effect that should be taken into account in a broad array of situations. Emile didn't say that it was an overwhelmingly powerful argument in all situations, nor did she come a little bit close to implying it.
...and nor did I criticize it for that. So where did this whole idea come from?
This makes no sense as a criticism unless you think it's claimed to be very powerful. If it can be weak, then sure, it's a fully general argument in favor of any status quo, and that's A-OK, and it's fairly obviously A-OK, so what are you complaining about? (this was edited to completely replace its contents)

I don't care, because there's nothing I can do about it. It also applies to all large-scale problems, like national elections.

I do understand, that that point of view creates 'tragedy of commons', but there's no way I can force millions of people to do my bidding on this or that.

I also do not make interventions to my lifestyle, since I expect AGW effects to be dominated by socio-economic changes in the nearest half a century.

I think that's a common misconception for not actually running the numbers. We individually have a very low chance of changing anything at large-scale problems, but the effects of changing anything in large-scale problems is enormous. When dealing with very minor chance of very major change, we can't just use our intiutions (which breaks down) but we need to actually run the numbers. And when it's done, like it was on this post, it says that we should care, the order of magnitude of changes being higher than the order of magnitude of our powerlessness.
Absolutely, shutting up and multiplying is the right thing to do. Assume: simple majority vote, 1001 voters, 1 000 000 QALY at stake, votes binomially distributed B(p=0.4), no messing with other people's votes, voting itself doesn't give you QALY. My vote swings iff 500 <= B(1001, 0.4) < 501, with probability 5.16e-11, it is advised if takes less than 27 minutes. Realistically, usefulness of voting is far less, due to: * actual populations are huge, and with them chance of swing-voting falls; * QALY are not quite utils (eg. other's QALY counts the same way as your own); * You will rarely see such huge rewards (if 1 QALY ~ 50 000$, our scenario gave each voter free $50 M ) So, people who 'need your vote' in real-world scenarios are either liars or just hopeless.
My town, with more than 1001 voters in each ward, had around twenty elections last year and two of them were decided by one vote. Your model says that this should happen somewhere in America much less than once in a billion years. The fact of the matter is, voters are not binomially distributed (sometimes this lowers the probabilities further, but sometimes it raises them a lot) Also, elected officials change their behavior based on margins, and on the size and habits of the population of voters. Politicians pay a lot more attention to vote-giving populations than non-vote-giving populations, for instance. The number of minor thresholds that can have some impact is large. And that's before you multiply the impact of your reasoning by the population who might follow it.
Let 20% wards be swung by one vote, that gives each voter 1 in (5 * amount of voters) chance of affecting a vote cast on the next level, if that's how US system works? Which is an exercise in reinforcing prior beliefs, since margins are obviously insufficient data. Are politicians equipped with a device to detect voters and their needs? If not, then it's lobbying, not voting that matters. Population following my reasoning: me. P.S. Thanks for hinting at other question, which might be of actual use to me.
This isn't a great assumption in general, but it's a particularly bad assumption if you're describing your reasoning out loud in public.
1 - No. This was an election for members of the town council, so those two 1-ballot-difference votes decided who got two jobs. 2 - I'm not sure what you mean there. A way of measuring the strength of this effect is to see how voting patterns differ between representatives who win by landslides vs representatives who squeak by. The vulnerable representatives act much more cautiously - and for good reason. 3 - Who voted in each election is public information, so the first answer is YES except for the requirement that there be a special device for it which you tacked on. For identifying your needs, there's exit polling (there is no way to make sure that you get exit-polled), in which you are often asked what the most important issue is for you. For other polling, I suppose you can lie and say you vote regularly when called, but you might consider that unethical. The simplest form of lobbying is letters to representatives. Again, I suppose you could lie. 4- Follow it, not you. The population of people who face the same situation with the same logical premises and habits. Copies of computations are the same computation. Perhaps you would find the fraction of people that would need to be voting so that your voting is no longer 'worth it'. Then you would vote or not with that probability.
So learning how 900 of the voters (other than you) voted won't shift your beliefs about how the remaining 100 voters voted in the slightest? No, I don't think so.
Politicians say they "need your vote" because they're talking to lots of people. Any one of them doesn't matter, but in bulk they really do.

I would probably get a "sceptic" label stuck onto me.

Global warming is not a single yes/no issue (even though a lot of mindkilled people like to pretend it is). Roughly I think it breaks down into five major questions:

  • Has Earth been warming up during the last several decades?
  • To what extent the warming is caused by anthropogenic factors?
  • How will the climate change proceed in the future and how certain we are of the forecasts?
  • What will be the consequences of the change in climate?
  • What should be done about it?

The answer to the first question... (read more)

Robin Hanson did an article which estimated this, but as far as I'm aware it's not "usually held" to be true. I've often found Hanson to be particularly incautious in his reasoning, and this is no exception. There are a lot of factors that this fails to account for (such as increasing ocean acidification and its various knockoff effects,) and I wouldn't put much stock in the specifics. There are certainly prospective benefits to climate change, but one thing I've often encountered as a rather substantial framing problem in the discussion is that people often ask "how warm do we want the planet to be?" when the important question is "what rate of climate adjustment most benefits us?" Since at our current rate we're adjusting global climate on a timescale of decades which ecosystems more commonly adjust to over timescales of tens to hundreds of millennia, the issue is not so much the temperate change, but the rate. I hear this viewpoint expressed frequently, but I find the "money" motive rather confusing. Getting university tenure is very difficult, and not that lucrative, whereas at least as of the time of my graduation, there were both more lucrative and more numerous openings available working in industry in sectors with a vested interest in continuing "business as usual" operations. Most academic climate scientists believe that anthropogenic climate change is taking place, and that it's liable to cause significant problems, yes, but that doesn't mean that if you want to enter the field and make money, you want to match the mainstream position in order to improve your chances of getting a tenured position, because most of the slots for professional academic scientists are already taken, and it's not a great way to earn money to begin with. In any case, academic scientists generally work less for money than for prestige. As a result, there's always reputational incentive not to adopt something too far from the mainstream position, to avoid being seen as a crackpo
My memories of this claim come from the Stern Review, I think. Yes, I agree, the uncertainty is high. It's not obvious to me that this is such a huge problem. Especially if you want to arrive at some "optimal" (according to certain criteria) state and not just maintain the status quo at any cost. I am not sure why. The "green energy" industry is rather massive by now. The government subsidies to the solar, wind, etc. businesses are huge. Trading carbon offsets is a profitable occupation. The Inconvenient Truth made Al Gore (even more) rich. Etc., etc.
Climate skeptics can also get money for their opinions by being employed at some "think tank". In a politically charged debate, anyone can be paid for having strong opinions. Perhaps one side has more money, but then it also has more competition for that money. Or you could try to make most money by first becoming a respected scientists, and then changing side. tl;dr: Let's focus on technical arguments, not on "they can make money", because that's true for everyone.
Unfortunately it's a bit more complicated than how much an individual can earn. Science, especially hard science, needs funding. Grants are what makes contemporary science happen. If you throw a couple of hundred millions at people who are actively working to prove X and only a couple of hundred thousands at people who are trying to disprove X, a couple of things will happen. First there will be lots of "statistically significant" results in favor of X and very few not in its favor. Second, people will quickly learn what kind of proposals do get grants and what kind do not. Stir and let stew for a few years and hey! you got yourself a consensus :-/
However, industry funds research as well as academia (indeed, sometimes in far greater degree.) Industry backed think tanks are quite well funded; although one could certainly posit political factors, it's not for a lack of money that they've failed to produce research that has swayed much of the scientific community.
It's really the primary problem of climate change. It's not that our current temperature is so great and the world would be worse if it were any other temperature, it's that ecosystems around the world, some of which we rely on, are adapted to a specific set of conditions, and it takes time for them to adjust to change. It's kind of like if you're driving on a big highway. You might want to speed up in order to get to your destination faster, and you can do so, by transferring to a faster lane, without any serious repercussions. But if you accelerate that much immediately while you're still in the same lane, the consequences are liable to be disastrous.
Let me repeat myself: it is not obvious to me that this is such a huge problem. There is little need for metaphors here, the situation is easy to visualize directly. Some ecosystems will adjust, some will not and will be replaced by other ecosystems. Unless you are very attached to the particulars of the status quo why is this horrible? Some forest will be replaced by grasslands, some grasslands will be replaced by forests. In some places the rainforest or the taiga will shrink and in others it will expand. The areals of plants and animals will shift. What's the big deal? If you are concerned about farming, the same reasoning applies. Some farms will get better harvests, some -- worse. Some farms might have to switch crops. Some might go out of business as land becomes not arable, but others will spring up on newly arable land.
Some ecosystems will be replaced by other ecosystems, but total biological and ecosystem diversity is likely not to rebound for millions of years (judging by comparable past climactic changes and mass extinction events.) Some ecosystems are liable to collapse and be replaced by dramatically impoverished systems, not just in terms of diversity, but in terms of total biological productivity. Reef ecosystems, for instance, are extremely biologically productive, but this productivity relies on highly sophisticated recycling of limited resources between species. If certain species die out, not only does that particular ecosystem die out, it takes millions of years for the level of species mutualism necessary to sustain such a productive ecosystem to evolve again. The same is true of a number of other ecosystems (although reef systems are particularly close to the edge right now.) When mass extinction events occur, it doesn't just result in other species immediately stepping in and adequately filling the niches that are now vacated. There's a time lag in which niches are left unfilled, or are filled by species which perform the roles in a substantially inferior way until they can adequately adapt to their niches.
Why are you assuming that the "total biological and ecosystem diversity" will diminish and what metric are you using for it? Wouldn't the reverse also happen -- some "impoverished" systems will get replaced by highly productive ones? Besides, is having a low-biological-productivity ecosystem bad in itself? Are you claiming that the climate change (as envisaged, say, by the latest IPCC projections) is going to be a mass extinction event?
My metrics for "total biological and ecosystem diversity" are the total numbers of ecosystems and species, and the degrees to which they're represented. As for why I'm "assuming" they will diminish, this the conclusion, not the presumption, of most of the research in that area. In broad terms, we should expect this kind of thing to happen because so many species are adapted very strongly to very specific niches. When circumstances change rapidly, those species are unable to cope, and die out, but there are no species which are strongly adapted to the new circumstances to adequately replace them. Because ecology is much more complex than a simple intersection of weather conditions, the result is that rather than ecosystems and species being shuffled around, a lot just ends up being lost entirely. But of course, there's a whole lot of research indicating specific ways in which this is already happening and is likely to happen in the future, outside the general principles that predict it. Yes, and over timescales of millions of years, with temperature increases, these effects would likely dominate. But over timescales humans are more practically concerned with, the dominance will tend to be in the other direction. As for whether a low biological productivity ecosystem being bad in itself, I'll simply say this. Some such impacts are likely to have significant direct influence on our economy. Some are not, and there are those who care deeply about them regardless, who are willing to go to great expense to prevent them, and those who are not, and regard such expense as worthless. But in my experience, I have not known anyone to regard those impacts which are unlikely to directly influence human economy as positive and worth paying for. Yes. By itself, anthropogenic climate change is unlikely to result in a mass extinction on the level of one of the Big Five, but it would still almost certainly be visible in the fossil record as a mass extinction event (I emphasize aga
What you call "conclusion" is probably a forecast, since we're talking about the future, right? Recent ice ages have advanced and retreated very quickly on the evolutionary time scale. Earth's various ecologies survived, for example, the last ice age just fine and the glaciation looks to me to have been MUCH more disruptive for temperate zones than a couple of degrees of warming are likely to be. I agree that we're in the middle of an anthropogenic mass extinction, the only thing is that it has nothing to do with climate change. It's just man taking over the planet. This mass extinction started thousands of years ago, goes on now, and will likely continue in the future. I think that whatever extinctions global warming may cause, they will be insignificant and indistinguishable from noise given the ongoing (non-climate) human impact.
In some cases, yes, in other cases, it's already observable as an ongoing process (I brought up reef ecosystems before because they're a particularly visible example of this.) The original onset of the first ice ages was indeed quite ecologically destructive and qualified as a substantial mass extinction event (although it was still much slower than anthropogenic climate change.) But virtually all species alive today are ones that have persisted through multiple glaciation periods. The flora and fauna of today's world are denizens of the ice ages. I should note that all of the points that you're raising have plenty of representation in the existing literature on climate change. It's definitely not the case that scientists don't think of these things. But these points are followed up with more research to determine what kind of expectations are warranted, and in some cases they're ones that merit concern.
Interpreted literally, this statement is obvious but useless. I expect you meant "it is something strictly between 100% and 0% and not particularly close to either one" (i.e. between 10% and 90%), which is a stronger statement, and not obvious a priori (not all trends have multiple unrelated causes). On what basis do you make that claim? I have heard it claimed that there is a consensus that the effects of warming will be positive through +2 C, but the sources making that claim seem to be quite short of a consensus themselves. Indeed. That doesn't answer the question, though.
Yes, I do. Earth has been warming up for a while (in terms of centuries) by now -- we're still coming out of the last Little Ice Age. On a more short-term scale for when we have direct instrumental data, I believe (from memory) that the current warming trend started around 1850 which is too early for CO2 to make a noticeable impact. And, of course, the graph of the global temperatures and the graph of the CO2 concentration in the atmosphere do not match too well. The short answer is that it's complicated and the temperature trends do not look like they're driven solely by the very evenly increasing CO2 concentration. As to not being 0%, well, physics. Not directly, no, but it does imply that the answer will be different for different groups of people.

I don't have any problems with the physics of climate change, that seems pretty clear.

I am worried about drawing conclusions about policy from predictive models. Causal modeling of time series data is very hard (according to at least some stats folks I asked who work with time series data). I don't know much about it, myself. I also don't know much about climate modeling.

1) The Earth is presently warming. I estimate that greenhouse gas emissions are a very significant component (~70%) of the long-term (100 years) climate change and a significant component (~30%) of short-term climate change (20 years). I think the IPCC is right, though this is largely because of their wide error bars (wide error bars should also be applied to my estimates above!)

2) It was presented as simple fact, and I accepted it. As I studied physics, my understanding became more nuanced, but nothing I found contradicted the initial impression. There wa... (read more)

Current beliefs on climate change: I would defer to the IPCC.

I would have first came across the subject while I was at school about 25 years ago (probably not at school, or at least only in passing). I think I accepted the idea as plausible based on a basic understanding of the physics and on scientific authority (probably of science popularisers). I don't remember anyone mentioning quantitative warming estimates, or anyone being particularly alarmist or alarmed.

My current views aren't based on detailed investigation. I would say they are based mostly on (... (read more)

My impression (which is only a handwavy impression, and I'll be happy to be corrected) is that climate-change "skeptics" used to say that there was no global warming, then that there was some but it probably wasn't anthropogenic, then that there was some and some of it was anthropogenic but that it was a good thing rather than a bad thing, and now that there is some and some of it is anthropogenic and it's probably a bad thing but the cost of stopping it would outweigh the benefits. In other words, that what's remained constant is the bottom line (we shouldn't make any changes to our industrial practices, economic policies, etc., to mitigate anthropogenic climate change), but the justification for it has become more and more modest over time, perhaps in response to strengthening evidence or to popular opinion. (Of course not everyone who can be categorized as a "climate-change skeptic" holds the exact same opinions; the above is intended as a rough characterization of what I think the typical "respectable skeptic" position has been.)

OK now I have to quote this:

Bernard Woolley: What if the Prime Minister insists we help them?

Sir Humphrey Appleby: Then we follow the four-stage strategy.

Bernard Woolley: What's that?

Sir Richard Wharton: Standard Foreign Office response in a time of crisis.

Sir Richard Wharton: In stage one we say nothing is going to happen.

Sir Humphrey Appleby: Stage two, we say something may be about to happen, but we should do nothing about it.

Sir Richard Wharton: In stage three, we say that maybe we should do something about it, but there's nothing we can do.

Sir Humphrey Appleby: Stage four, we say maybe there was something we could have done, but it's too late now.

  • Yes, Minister

(Note I don't mean this is an intentional strategy as applied to climate change, even one operating at a subconscious level within individuals. Given a range of skeptics with different opinions, it could be that different ones are coming into the spotlight so that the "most defensible" argument for doing nothing appears at the appropriate time. I just thought the parallel was funny.)

Funny - a lot of the skeptics complain about the same tendency among people who want to halt industrial capitalism - it's one of the biggest sources of grumbling I see.

I am extremely skeptical of AGW alarmism. Here are some reasons:

  • I am intrinsically contrarian.
  • My understanding of AGW is superior to the large majority of people of I talk to about it. For example, very few people understand basic concepts of temperature, blackbody radiation, and Wien's law. Very few people understand why C02 molecules are worse than 02, N2 or CO molecules for warming, or why methane molecules are much worse (the reason is that C02 has many rotational degrees of freedom, which allow it to absorb IR radiation emitted by the Earth). The
... (read more)

I'm skeptical of various parts of AGW (e.g., Climategate) but I believe the reaction to the field has become a hate death spiral. (Hence, considering it in its separate parts rather than a single phenomenon.)

Accordingly, I find some of your reasons unconvincing.

Building on the above point, if half of contemporary research results are wrong, then the likelihood that the complex multipart AGW argument is wrong is very high.

Fully general counterargument.

Climate scientists have never made a public falsifiable prediction.

IPCC Scientific Assessment

Regarding the confirmation of the second and third assessments (that is, they failed to be falsified, which implies that they were in fact falsifiable):

"Comparing climate projections to observations up to 2011"

In conclusion, the rise in CO2 concentration and global temperature has continued to closely match the projections over the past five years, while sea level continues to rise faster than anticipated.

You don't find any falsifiable predictions if you never look for them.

There seem to be problems with that paper.
I believe you'll find the peach line (the non-adjusted data) in figure one still tracks with the projections. As far as I can tell your link is only concerned with the adjustments, but feel free to correct me if I'm wrong. EDIT: At most, I believe we're reduced to debating the meaningfulness of the word "closely".
Sorry, I don't have time to dig through the mound of literature. Could you please just state what the falsifiable prediction is? Please be as precise as possible.
No, the people with the strongest background in climate science are climate scientists themselves, who are often quite alarmist. Half of published research results are wrong, but consensuses of scientific fields have a much better track record. Economics does not work that way.
I'm no expert, but I've read the IPCC reports, and they're (to their credit) about as dry and anti-alarmist as it's possible to be while making the predictions they do. Are you talking about informal predictions? If so, which?
I believe he means that the IPCC reports are in agreement with some people who you may classify as "alarmist". Or you can read it to mean that while the tone of the reports is not alarming, the actual contents are. edit: That'll teach me to reply to a post without refreshing the page.
By "alarmist", I meant making dire predictions, not sounding panicked when they do or something like that. I assumed Daniel_Burfoot meant the same.
If you don't mind, I would like to probe your usage of this term... What distinction do you draw between "alarmist" and "alarming"? If the hypothetical situation is such that the truth really is properly dire, are accurate reports of this dire truth best classified as "alarmist"? How should you react when, one night in the laboratory, you make an alarming discovery with fairly high confidence? After having them independently verified, would you consider yourself an "alarmist" for reporting your own findings?
Maybe I should have avoided the term "alarmist" in that context, since it often implies unjustified predictions of danger, which I obviously did not mean to imply. I'm not interested in arguing over definitions.
Good, I just wanted to be clear. In my experience that "alarmist" usually does strongly imply that the predictions of danger are unjustified, and that interpretation (which I presume most readers default to) risks changing the intended meaning of your statement that "climate scientists[...] are often quite alarmist." Now that I re-read your top-level post knowing what you meant, I think I understand much better what you are saying.
Is this a reason, or a bias? How would you update your beliefs if you learned that this statement is false? Would you therefore like to offer me the odds on a prediction that, if we investigated the funding sources of various pro- and anti- AGW campaigns and think tanks, we would find that oil companies are predominantly sponsoring pro-AGW think tanks and stronger emissions legislation?
A prior ;)
Oh, they have made falsifiable predictions which mostly got falsified, at which point everyone (prominently including the media) got a severe case of amnesia :-/ An example would be the Trenberth's claim about the increasing strength of hurricanes around 2005.
I think it's better to make forecasts that are later proved wrong, then acknowledge that they are wrong, make new forecasts and appropriately calibrate the new forecasts based on the lesson learned in humility from the first wrong forecast. Trenberth in particular seems to be a fairly honest and open climate scientist, in that he made an explicit forecast, then later admitted a change of mind. He's also the person who admitted (within an email leaked by Climategate) that there was a problem with balancing the energy budget, and he later publicly noted the same, and tried to come up with an explanation. The problem isn't with people making wrong forecasts, it's with people (a) refusing to make forecasts while still implicity doing so by claiming near-certainty about the future and seeking action based on that, or (b) making forecasts and insisting on the forecasts being treated as correct without an external test of validity or a past record of forecasting expertise. See also:
Yes, of course it's better to try and fail, and try again, and fail better... The situation with global warming reminds me very much of a recent Yvain post on his blog about the "motte-and-bailey doctrine". I think the AGW proponents use this technique extensively.

The cause of my original beliefs on climate change is my parents' politics.

In my larval form, I had many more common misconceptions about how the greenhouse effect was supposed to work. The most wrong, and also the only one that I actually changed because of an anti' web site, was that the cycle of historical CO2 was a cause of historical climate changes, rather than an effect. Otherwise, I learned much more from RealClimate than I did the antis.

There was a distinct moment when I figured out that global warming was a physics problem that I could actually u... (read more)

I'm an economist and think that the challenge of macroeconomic forecasting tells us something about the difficulties of creating mathematical models of the climate. I don't think we have the ability to make accurate mathematical models of complex systems where we can not conduct experiments to calibrate our models. But I recognize that I know little about climate models and so am not highly confident of my beliefs.

What are your current beliefs on climate change? Specifically, would you defer to the view that greenhouse gas forcing is >the main source of long-term climate change? How long-term?

I have no particular opinion about that. I think any specific predictions are more likely wrong then true, especially predictions about climate change economic effects, and catastrophic predictions are almost certainly wrong. I strongly oppose emissions cut policies.

What were your beliefs on climate change when you first came across the subject, and how did your views e

... (read more)
What do you think are the reasons you and your country see it as obvious? It doesn't seem obvious to many people.

What are your current beliefs on climate change? I think it most likely that the experts have it roughly correct: the climate is warming, there's a lot of noise on short timescales, a big influence on overall temperature is how much CO2 there is in the atmosphere, a big influence on that is emissions from human activity like burning coal, etc. I would not be greatly surprised to find that the current consensus is a factor of 2 out either way in magnitude (nor, I think, would the experts) but I would be surprised by a factor of 10.

What were your beliefs on ... (read more)

What are your current beliefs on climate change? Specifically, would you defer to the view that greenhouse gas forcing is the main source of long-term climate change? How long-term? Would you defer to the IPCC range for climate sensitivity estimates?

I'm fairly confident about the sign, but not the magnitude of climate change. I'm not sure that greenhouse forcing is the principle component. IPCC estimates seem pretty reasonable since they were scaled down a while back.

What were your beliefs on climate change when you first came across the subject, and

... (read more)

When I was young I was quite the environmentalist, but I grew out of it around age 7 or so(~1992, when it was still fairly new). Didn't have much of a rational basis for it(truth be told, the moment I remember was reading a book by a lady named Harms, and thinking that didn't make any sense for someone named Harms to be doing something I so strongly associated with helping, so I drifted off to other things to geek out about instead - yes, I was a strange kid). I sort of dropped AGW with all the other baggage of that era for many years.

Didn't think about i... (read more)

Meta: I don't think questions need to have "[QUESTION]" in the title. That's what the question mark does.

It's to indicate that the post is not too substantive in and of itself, and is mostly a bleg. Sort of like people put LINK: in front of posts that are basically just for sharing a link.

I used to just trust the word of the experts, because I am not an expert and had no incentive to become one. I didn't have a lot of faith in such a politicized science, but reasoned it was probably better than anything I could come up with. I trusted the IPCC reports, but after reading about Climategate thought they were exaggerated a bit as a means to gain political power.

Recently I've started to consider investing in alternative energy. Given that most alternative energy (especially with the fracking and shale oil revolutions) is based on AGW being a ser... (read more)

What are your current beliefs on climate change?

I'll skip talking about my own general beliefs about climate change because there's little reason to think they're of much more interest than those already posted.

Instead I'll point to the results of the last LW survey, where hundreds of us answered the question, "What is the probability that significant global warming is occurring or will soon occur, and is primarily caused by human actions?" The question isn't very specific and is somewhat subjective, but the answers to it can be correlated wit... (read more)

Obviously, your initial views wouldn't have included beliefs about terms like "greenhouse gas forcing"

In my case this is wrong. Carbon dioxide absorbs infrared? Duh. The only change in my views since the beginning has been learning that the role of clouds is unclear (they may contribute some negative or positive feedback, depending on which types increase or decrease in prevalence). That increases the error bars for magnitude of warming, but that's in line with IPCC forecasts. Since solar forcing seems unlikely to change that much in the ... (read more)


To a significant extent I defer to the IPCC and other bodies on whether AGW exists. But as Holden Karnofsky says:

I generally find it very hard to formalize and explain what “outside views” I am bringing to a decision, how I am weighing them against each other, and why I have the level of certainty I do in each view.

[This comment is no longer endorsed by its author]Reply

New to LessWrong?