DrCloud

Yes. Everyone here is pretty well on track, but there's considerable imprecision in the language. For example, they don't really "release" CO2; they create it in the combustion process and it flows out the tailpipe. As noted, because the combustion is imperfect, they also create and emit CO as well as (due to the high pressures & temperatures in the cylinders) oxides of nitrogen, NOx (x=1,2, mostly). "Burning" things (or "combusting" them) oxidizes them, so burning molecules containing carbon oxidizes the carbon into CO2; because the complex hydrocarbons in gasoline also contain hydrogen, cars also create and emit water vapor. Ideally, that's all they'd emit, but with the imperfections in the process, there's the other stuff, too. Vehicles, generally, emit something in the vicinity of 20% of all the CO2 that gets put into the atmosphere via activities involving humans (I don't remember the exact figure; it could be as high as 30%). Power plants big contributors, too, as are wood/coal fires in developing countries. HPH

The general answer to the original question is "proxy data." By this, it's meant that various indicators preserved over time are used to infer ancient temperatures -- oxygen isotope ratios and tree-ring widths being a couple. Others include distributions of critters and plant material in sediments and ice. Necessarily, these inferred temperatures are both less precise and less accurate than modern thermometers; nonetheless, they are self-consistent and useful in reconstructing the behavior (particularly relative behavior) of past climates. It's important to understand the difficulty of this: not only is it necessary to translate the proxies into temperatures (or, more often, temperature deviations from some base), but the timing of the temperatures must also be established. After all, thermometers aren't the only thing that's new in geological terms, so are clocks. So getting the time scale right for the inferred temperatures is also quite challenging and also leads to additional uncertainties in absolute terms. Because of these uncertainties, some people enjoy minimizing the usefulness of proxy datasets. This, however, speaks more to their lack of knowledge about the field of paleoclimatology than it does to the datasets themselves. Understanding Earth's past behavior requires using all the information we have available, in the context of its limitations, and proxy data is all we have in the era before thermometers. HPH

^ Yep. This is one of the easiest calculations to do, and it's usually introduced early in a physical geography class to illustrate how Earth's atmosphere, via its greenhouse effect, makes the planet habitable. Using the power of the Sun (at our distance from it), the observed planetary albedo, and the blackbody radiation principle, the surface temperature with no atmosphere comes out at about 255C. Now, this includes no water vapor (a potent greenhouse gas) in any kind of "atmosphere"; however, it also uses the observed albedo, which is somewhat lower than it would be at this low temperature. These two omissions tend to cancel each other, and the albedo effect would dominate so that the actual temperature would be even colder. Oceanic heat absorption has nothing to do with it, as this is a steady-state calculation, and water's heat capacity comes into play only when you're concerned about rates of heat storage or about moving heat around. I posed this in the hope that the OP would clarify his question. Life without a significant atmosphere is one of those questions that exobiologists love to speculate over, but you need to specify the boundary conditions carefully. HPH

Right distance for what? With no atmosphere, Earth's average surface temperature would be down around 0F, meaning most of whatever water you're stipulating would be frozen. Of course, if your planet were closer to its sun, perhaps there could be a pure water atmosphere (at a pressure equivalent to whatever vapor pressure the temperature of the liquid water would allow). Although the stratospheric ozone keeps us air-breathers out of harm's way as far as UV radiation is concerned, so would a pretty thin layer of liquid water, so this isn't an issue for your planet. With no atmosphere, there wouldn't be any significant amount of dissolved oxygen in the "ocean", but anerobic life exists on Earth. Asking whether life would survive implies something about pre-existing life -- as in, would any of Earth's current life forms survive under those conditions? That's not the same as asking whether life in some form could develop under these conditions. Finally, remember the curious life-forms that have been discovered in the deep ocean around the hot vents on the mid-Atlantic ridge. It's doubtful that they "need" the atmosphere in any real way. On the other hand, the processes that they do need could well create an atmosphere over time. So the question seems more complex than it might appear. HPH

Controversy, in the sense of "a dispute, especially a public one, between sides holding opposing views" is generally limited in our community to issues in which the opposing sides have a stake. Until recently, that was the case with whether or not global warming is happening, because the skeptical side, many supported by grants and/or outright salaries by big energy, had a job to do. In recent years, they've come across to those of us who understand the science like the apologists for the tobacco companies did for so long, those who denied the lung-cancer / smoking links. In the case of interest here, "controversy" is just too strong a term. And a wait-and-see attitude is fully appropriate. That attitude is appropriate for other issues in meteorology and oceanography as well, such as whether hurricanes are going to be more numerous or stronger as the climate warms. Evidence is coming in, but it's still too soon to make a final judgement. HPH

Well, c'mon, now, Martin -- you're working awfully hard to tout a controversy that's unlikely to be all that controversial. First, the sediment core really says nothing at all about European climate, just the composition and conditions of the ocean over time (temperature, salinity and so on). Inferences about what happened when (and to whom) are based on time reconstructions of these sediment cores, and there are pretty large uncertainties in what's synchronous with what. Further, correlations do not cause and effect make (that's the reason these guys used model simulations -- you can do actual experiments that way). Second, the "urban myth" part of this can easily be overwritten with a solid explanation such as the one in the articles, but the nomenclature can still hang on. Use of the term "greenhouse effect" is an example of this: greenhouses really don't behave the way the atmosphere does, because they have (glass) lids that keep convection from carrying away the heat in them. (Yes, the glass lets sunlight in and tends to prevent IR from escaping, just like atmospheric greenhouse gases do, but it's been shown that suppressing the convection is how they really work.) But despite this lack of precision in naming the phenomenon, the terminology is in common use. I would anticipate that "the Gulf Stream keeps Europe warm" will hang around long after most people in the climate community understand that it's really the maritime climate that does it. It's no big deal, really. Compared to big physics and chemistry, not to mention medicine, the climate research community is a small group of folks, most of whom know each other pretty well. They get a lot of amusement out of little studies such as this, and I doubt there will be anything resembling real controversy. Now, I hijacked the thread a bit by introducing this new article, and I'm sorry for that -- I thought the new information might be of interest. But it does illustrate how people who go ballistic at the prospect of climate change because they construct a tenuous chain of events leading to a "Day after Tomorrow" like catastrophe are often only looking for self-promoting publicity. To get all hot (sorry, bad pun) about it is just to fall into their trap and give them what they're asking for. HPH

it has been typical of the approach of the climate skeptics -- both professional and amateur -- to deny the existence of both relevant data and informed analyses that do not support their positions of denial. In this case, perhaps we should be charitable and allow the possibility that internet connections to New Zealand somehow do not provide links to the National Academy of Sciences site here in the US. I assure other readers that the link in my previous post works just fine and allows interested parties access to the definitive report on the Mann et al. "hockey stick" temperature curve. Given the previous post, I have no further use for this particular thread or any other involving that individual. HPH

Although our colleague from New Zealand has undoubtedly undertaken an exhaustive review of the Mann et al. temperature reconstructions to reach his conclusions, these conclusions are at some variance with those of the US National Academy of Sciences as discussed at length in this recent report. HPH

Here is the link to the article, but, like most new publications, getting the full article requires either a subscription or a purchase. (The technical article on which this is based is in the Quarterly Journal of the Royal Meteorological Society, 128:2563-2586 -- and this is a top tier technical journal.) American Scientist is the bi-monthly publication for Sigma Xi members, but some libraries probably have it. At that link is a figure that tells part of the story;another part is this picture, which I lifted from Am. Sci. (forgive me, oh Sigma Xi gods...): This shows results from two different climate models (the orange and the green) that have been calibrated to observations, showing how they transport heat northward. Heating is the gradient of these heat transport curves, so the maximum heating associated with the oceanic transport is south of 40 degrees. By contrast 45N is southern France, and 60N runs through the Shetland Islands, just off northern Scotland -- it's the atmospheric transport that's doing the heating in the latitudes of Europe. I don't want to suggest that this new paper is the last word on the issue, and it's certainly the case that "the Gulf Stream keeps Europe warm" is not a concept that's going to die easily. But it's interesting, and the arguments, both from models and observations, hold together. If it's proven out, it'll cause any number of textbooks to be re-written. HPH

There's an interesting article in the new issue of American Scientist that makes an intriguing case for this: the warming of Europe (relative to, say, Labrador) by the Gulf Stream and its extension (the N. Atlantic Drift) is the climatological equivalent of an urban myth. (American Scientist is a general-scientific-audience publication, rather like Scientific American, and the article is a summary of work reported in several technical journals.) This conclusion is based on computer simulations with and without a Gulf Stream, which show that the main reason that Europe (and NW N. America) are warmer than regions at the same latitudes on the west sides of the respective oceans is simply because of the maritime climate -- the greater thermal inertia of the oceans keeps the air coming off them from varying as much as the continental air that governs the climate of north-eastern N. American and north-eastern Asia. Winters are warmer in London and Seattle, and summers are cooler, than in Tornonto and Vladivostock. Further, in the case of Europe, the downstream effects of standing waves in the Jet Stream set up by the Rocky Mountains enhances the effect of the maritime climate by nudging the prevailing winds to come from the southwest a bit, making the European climate all the more equitable. This is relevant in the current context because it ameliorates concerns about the effects of turning off the thermohaline circulation, as might have happened with the draining of this glacial lake and could happen with global warming. (Generally speaking, Martin's reasoning is just fine -- except it, and the Science article, rely on this urban myth.) Now, this doesn't speak to how Europe might warm or cool. Model simulations of warmer climates have suggested increased snowfall over Europe (it's warmer, but still below freezing, and it snows more); and this could well result in a cooler Europe simply because the increased snow cover would increase the surface reflectivity and prevent the sun from doing its job. But this has little to do with the Gulf Stream or the "conveyer belt" overturning. All this is to say that the jury is still out on some of these second-order effects of global warming as well as on certain paleoclimatological connections. HPH