Fight my ignorance re: Global Warming

Great Debates
1

(Inspired by this thread, which has turned into an off-topic pile-on.)

Okay, I get humans create greenhouse gasses (etc.). And I get that the climate is changing.

But here’s where my ignorance comes in: I’ve never seen any good link betweeen these two events besides cum hoc ergo propter hoc.

Most arguments run like this:
a) Humans create CO2 and other gasses that have the potential to change the environment. And they destroy the ozone layer. And… (etc.).
b) These charts show that the climate has changed rapidly since industrialization.
c) Ergo, humans have caused the climate change.

Does anyone else see the fallacy in this?

There must be a reason why the vast majority of climate scientists favor the human-caused-global-warming model over the coming-out-of-a-mini-ice-age model, which also seems reasonable. Will someone please explain this reason to me?

I’m putting this in GD because it seems like the debate still rages on. If a mod sees fit to move it to GQ, I, of course, would be honored.

Also, I’m a ‘guest’ on this forum, so I can’t search old threads. If there is a good explanation of this in an old thread, a link would be appreciated. But please don’t just point me to a site/thread that simply cites experts who don’t explain the crucial link. I can find tons of those on my own.

Fight my ignorance!

2

I’ve been thinking about posting this for a week, and have scanned the forum for threads every day. Of course the day I actually DO post it, I notice this thread immediately afterwards.

But upon reading, the thread again just cites experts who are pretty sure that humans are causing global warming. No science backing it up.

There must be science. They’re scientists for heaven’s sake. Does anyone know how the scientists link human activity and global warming?

3

The basic connection is that carbon dioxide and the other so-called “greenhouse gases” which humans are producing have a known effect on climate. Simply put, these gases trap the heat that is produced by sunlight entering the atmosphere and prevent it from being re-radiated back to space. Therefore the atmosphere heats up. That’s your causal link.

Of course it is more complex than that, but that’s the key connection.

4

The attempt is made to model the climate and see the effects of carbon emissions (primarily CO[sub]2[/sub]) and check if those match up to empical trend measurements. It is, frankly, something of a voodoo science (in the emergent science, not pseudoscience sense), particularly as there is really no default baseline “normal” state, but in the past decade or so high performance computing combined with massively parallel processing methods and advances in complexity theory (necessary for representing complex, highly nonlinear systems) have allowed representation to a high degree of fidelity and extrapolation to past and near future data which can then be compared to the models.

The result is an overwhelming consensus among climatologists that there is unquestionably a warming trend in the global climate, and an increasing consensus that there is at least some component–perhaps a majority, driving one–which is anthropogenic (caused by people). There is considerable debate as to the extent that the future trends will diverge from present values, and how much this could potentially be mitigated by sharply reducing carbon emissions in the near future; the models behave dramatically different depending on the initial parameters and driving impulses, and there is no easy way to discern the correct values other than plugging in a range of them and comparing to existing (and often sparse beyond a few decades back) data. Such debates, however, are like arguments between two evolutionary zoologists about whether zebra’s stripes are for camoflage or herd recognition; neither of them doubts the fundamental theory of natural selection, just the application of it.

Climatology is a vast, diverse field borrowing from many subdisciplines of physics, chemistry, geosciences, and mathematics, and it’s really impossible for any one person to speak in expert depth on all of these areas, hence both the disagreement and inability to break the subject down into small, nontechnical explanations that are testable by the average man-on-the street. Among the general public, actual technical knowledge of the field is essentially nonexistent; hence, the debates on the topic tend to resemble religious arguments with each side appealing to faith and/or FUD to garner support.

It is, in fact, almost impossible to have a civil discussion on the topic (witness the previously cited thread) because one side or the other–sometimes both–will resort to various falicious arguments to avoid acknolwedging that they are beyond their personal body of knowledge on the topic. (This resembles arguments in the 'Eighties regarding the possibility of nuclear winter.) Since appealing to rationality doesn’t work when someone lacks actual facts, and attempts to educate are often viewed as challenges or patronizing, there’s reallly no where else to go. Even suggesting that the facts are incomplete–that while we know that changes are happening, we don’t have a full grasp of the extent of them or lack thereof–sends some in to a frenzy of accusations of complicitness.

It doesn’t help, in this sense, that one of the primary figures promoting awareness of global climate change is a partisan political figure whom many people are inclined to disbelief by default; I think Gore is mostly sincere in his appeals (with just a moderate amount of self-serving attention-whoring), but he’s also not trusted by many people who have a pre-existing conservative or libertarian bent, thereby exacerbating an already existing rift on the issue between self-identified liberals and conservatives. It doesn’t help that some parts of his explanation are “dumbed down” to the point of being conceptually wrong, thereby giving opponents a justifiable wedge to argue against his statements.

So, there is actual science, and while the answers aren’t as clear as calculating the trajectory of a cannonball fired at 35 degrees with an initial velocity of 200 ft/sec, the leading experts in the field general concur that some kind of human-produced global climate change is occuring, that it will continue to occur, and will be exacerbated by projected carbon emission trends. How bad it will play out and what the cost vs. benefit actually are for various proposals (or complete inaction) is an unknowned, but the predictions, for what they are worth, keep shifting toward the more discouraging end of the “bad” spectrum. The Wikipedia article on global warming has extensive external references and citations, which should be sufficient to get you started in learning more on the topic and make an evaluation of your own.

Stranger

5

Stranger, thank you for your considered and eloquent reply! A pleasure to read.

But I still feel like my question is hanging out there. And reading through your reply, and the linked wiki, I think I may have refined my question.

(By the way, Colibri, you, as a climatologist(?) may be uniquely qualified to answer this.)

The writings and arguments that I find to be guilty of resorting to cum hoc ergo propter hoc may be simplified for the benefit of the layman reader. But they never seem to be dialogical. They never (or rarely) address the common counterarguments, the most compelling of which I find to be the idea that the Earth experiences natural climate fluctuations, one of which we are currently experiencing.

Colibri, I understand the (simplified) science. I know that carbon dioxide absorbs heat in a way that nitrogen, oxygen, and argon do not. But the degree to which this affects global climate change has, I think, not been addressed. What am I missing here?

6

That’s only a fallacy if there is no mechanism that relates CO2 to temperature. That’s not true in this case - though the extent of the impact may be in question, as is atmospheric mechanisms to absorb excess CO2.

The ozone layer is an interesting case, since the theory said flurocarbons were responsible for the hole. We did an experiment in reducing them - and the hole reduced also. That had ample potential to falsify the theory; since it didn’t, we can be fairly sure there is something to it. I for one would like to do the CO2 experiment. If it fails, we’re out some money. If we don’t do it, and we’re wrong, we might be out a lot more.

If the temperature increase was only due to being in an interglacial period, it should resemble that of other interglacial periods. You can check if it does.

7

If you’ve seen An Inconvenient Truth, you’ll know he does directly address that. Since he got his data from some science, I can only assume this point has been addressed. If the anti-global warming faction is anything like the creationist faction, the fact that an argument has been already addressed does not mean that they’re going to stop making it.

8

You’re absolutely right. I guess I’ll need to modify my complaint:

Eek! Me?

9

I haven’t seen the movie, and probably won’t be able to do so for some time.

How does he address this issue (my confusion)?

10

No reputable scientist thinks that humans alone have caused the climate change. No one know how much *over-all *change humans have caused. It appears that humans have caused most of the recent warming, but there is much disagreement on the other factors and other parts of the over-all changes (There’s more to Global Warming than just warming!)

Here’s a quote from the recent report:“The observed widespread warming…support the conclusion that it is extremely unlikely that the global climate change of the past 50 years can be explained without external forcing,and very likely that it is not due to natural causes alone”.

See this thread:
http://boards.straightdope.com/sdmb/showthread.php?t=406706&page=1&pp=50

11

I saw it just last week, waiting way too long. He shows temperature curves from Antarctic ice cores, stretching back beyond previous ice ages, and shows the temperature and CO2 fluctuation - and then compares them to our present situation. I have no idea of how accurate his presentation is, but he does address it.

I wish he had done a better job of addressing the economic impact of CO2 restriction. That part I found weak.

12

Interesting. Most anthropogenic contrarians (is that the word?) use exactly the same evidence to support their arguments that our “current” ice age is similar to past ones. Obviously, I’m not qualified to interpret the ice cores myself. but one can dream, no? It’s really amazing that different scientists can look at the very same data and come to opposite conclusions. Or maybe I’m just being naive: this is a politically charged issue after all.

I just read a factoid from a link in one of the other TWO ( :rolleyes: ) global warming threads: someone compared the mainstream climatologist recommendation to Gore’s Plan, into the next hundred years. Plan A has the planet warmer, but improving in 2100, and moderate economic impact. Plan B (Gore’s), has climage change radically changed, and Earth’s population an average of 30% poorer – including already poverty-stricken countries. No wonder the issue swirls with politics.

13

Randy, here’s the relevant clip from An Inconvenient Truth which discusses ice core samples that tell us the CO2 concentrations dating back 65000 years through several ice ages.

14

No, I’m not a climatologist but an ornithologist and tropical biologist. I have, however, been involved in global change research from the point of view of its effect on tropical forests and on biodiversity. I have also been following the climatological debate rather closely for the past 30 years or so. (As I have mentioned elsewhere here, I served as a representative on a government committee on global change research in the early 1990s, and also for a time was the director of a major global program of research on tropical forest dynamics and ecology.) In my opinion, global climate change has shown some clear effects on species ranges, ecology (such as flowering or migration seasonality), forest composition, and other features; there is now a substantial body of published research on the subject. Although species have had to contend with climate change in the past, the threat now is the unprecedented speed at which the current changes are taking place; too fast for many species to adapt or migrate.

In fact, weather and climate are such “noisy” phenomena that it has been difficult to clearly identify trends; it has take decades of intensive research to make it clear that the present episode of climate change is outside the norm. In fact, the present period is unprecedented within the last 600,000 years, perhaps more, a period which embraces several glacial and interglacial periods.

Previous episodes of global warming can frequently be linked to elevated levels of carbon dioxide or other greenhouse gases, often due to intense volcanic eruptions or other geological events. These natural causes of global warming are either absent now or not intense enough to account for the present episode of warming.

The relationship of increased atmospheric carbon dioxide to global warming is complex, which is one of the reasons modeling has been so difficult. There can be intricate positive and negative feedback loops. For example, higher sea surface temperatures cause greater evaporation, resulting in increased cloud cover, which can result in greater reflectance of sunlight and therefore counteract the warming. Also, other phenomena, such as particulate matter in the air due to pollution, can block sunlight and counteract warming. In fact, it is my understanding that the actual amount of measured global warming is less than what would be expected from the increase in atmospheric carbon dioxide had these factors not been present. But although these factors result in some continued uncertainties, it now seems clear that increased CO2 will result in increasing global temperatures for some time to come.

15

The graph he shows in the film indicates a cyclical patern of CO2 concentration in the atmosphere, followed by a similar cyclical patern of temperature change that lags a little behind the CO2.

He shows the graph up to a certain point (some time in the very near past), basically illustrating what the “normal” cycle of warming and cooling of the Earth looks like. Then the graph adds on the most recent century or two, and the CO2 levels shoot up dramatically; significantly higher than they have ever been (and are still rising). The temperature hasn’t increased in a similar fashion (yet?), but there is a certain amount of lag time between CO2 level increases and temperature increases. It was a pretty damning and pretty scary illustration, IMHO.

16

As others have noted, there is certainly much more to the claim that humans are responsible for the climate change than noting a simple correlation. In fact, there is a whole subfield of climate science called “detection and attribution” dedicated to trying to study the observed changes and to attribute causes to them. The previous (Third Assessment Report) of the IPCC dedicated an entire chapter to this subject and I imagine the new one coming up (of which we so far just have the “summary for policymakers”) will too.

I would summarize some of the basic points as such:

(1) Evidence (and modeling) suggest that the internal variability in the climate system, at least as it relates to the average global temperature, is fairly small…i.e., if one sees a significant change, then it is due to some natural or man-made forcing on the climate system. So, for example, the Little Ice Age is understood as being the result of slightly reduced solar activity coupled with some pretty major volcanic eruptions, both which favor cooling.

(2) We have increasingly good estimates of the magnitude and sign of these various forcings as we get into the modern era (20th century, and especially the satellite era). For example, we are measuring the luminosity of the sun very carefully now. And, we understand well the radiative forcing produced by a given level of greenhouse gases. Natural forcings do not seem to account at all for the strong warming seen over the last ~35 years. E.g., in the computer models, one needs to include the estimates of the forcings due to greenhouse gases in order to get good agreement between the models and the observed record over that period. (See, for example, here for a nice visual illustration.)

(3) While it is theoretically possible that the observed warming could be due to some unknown forcing that we haven’t yet understood, there have so far been no viable candidates that seem to explain the data quantitatively in the way that the greenhouse gas forcing does.

(4) Furthermore, one would not only have to have such an alternative candidate mechanism put forward but would also have to explain why the known mechanism by which greenhouse gases cause warming is somehow not operating…or is largely cancelled out. Richard Lindzen is a prominent skeptic who put forward a hypothesis called the “iris effect” whereby a negative feedback due to clouds in the tropics would cancel out much of the warming due to greenhouse gases. However, Lindzen’s hypothesis (in the sense of the specifics regarding the behavior of tropic clouds) has apparently not held up very well in the scientific community. Also, with any strongly stabilizing feedback mechanism of this kind, one is left with the conundrum of trying to explain the past climate variability…e.g., it makes it very difficult to explain how the the earth’s orbital variations coupled with changes in greenhouse gas concentrations would have been large enough to produce the warmings from the ice age to the interglacial periods. [Also, the climate models with their current sensitivity to forcings have been successful in reproducing, for example, the cooling effect seen for a couple of years after the Mt. Pinatubo eruption in the early 1990s and this probably wouldn’t be true if such a stabilizing mechanism were operating.] In other words, Lindzen’s hypothesis seems to suggest a climate system that is much more stable than what is actually observed.

(5) There are also many features regarding the pattern of the warming that seem to be well-fit by warming due to greenhouse gases and not generally so well-fit by other possible mechanisms. For example, the current warming has been accompanied by a strong cooling in the stratosphere, whereas an increase in solar luminosity would lead to warming in the stratosphere too. (The interpretation of the data is complicated a bit by the fact that some of the cooling in the stratosphere is due to the ozone-layer-destroying CFCs. However, the best estimates are that this cannot account for all of the cooling that has been seen.)

I am sure an actual climate scientist could throw in some more pieces of evidence, but that gives you the gist of things…and, hopefully some idea that the evidence for anthropogenic global warming goes far beyond simply noting a correlation and suggesting that this must imply causation.

17

Since it seems that the vast majority of qualified scientists (a set I’m not a member of) agree with global warming, you need to check on the few that don’t. Are they in the employ of companies against it? Are they ideologically against it? Have they established a niche position, with lots of media attention, by being one of the few contrarian sources. You need to look at the date of the reference also - I’m under the impression that people who have been waiting for more evidence (quite a reasonable position) have become convinced in the past couple of years.

A good analogy might be those who claim smoking is not all that harmful.

I remember how Detroit claimed back in 1972 that making fuel efficient cars would kill their profitability. It turned out that not making them killed their profitability. The first companies that make hardware to reduce carbon emissions, or perhaps good solar cell technology, are going to make a ton of money. I fear these will not be US companies. In the global marketplace, the backwardness of Washington is not going to slow the march of progress for long.

18

I’d like to render my warmest thanks to everyone who has posted so far; I think my ignorance has been valiantly fought. (Thanks especially to Colibri and jshore for their lengthy and eloquent replies.)

However, I do wish someone from the other side of the debate would post some counterarguments. I hate to fill my knowledge-void with only one side of a polarized issue (no matter how reasonable that side may be). I won’t consider my ignorance conquered until I’ve heard both parties’ thoughts on the matter.

Unfortunately, it seems there are very few dopers who come down on the side of the contrarians. This seems like a pretty strong argument in and of itself: the average doper is pretty freaking smart.

19

You can see contrarian opinion in the very thread that you cited (although it is a guest, not a member). By and large, the anti-GCC contingent snipes away at bits and pieces, prying at disagreements in scope and magnitude between climate researchers. The fact that the majority of climatologists agree that there is a significant degree of anthropogenic climate change means that [list=a][li]Global climate change and warming is probably real,[/li][li]Everybody is making their models based on a basic misunderstanding of climate behavior, or[/li][li]It’s all a big conspiracy by the Communists/hippies/Bill Cosby to impose a socialist agenda on a one worlst state/create a rationale for legalizing pot/sell more Jello-brand pudding products.[/list]I’ll leave it as an exercise for the reader to work out the probabilities of each of these options.[/li]
Stranger

20

Why can’t it be both, like the late Earl Warren?