The second post on this site - the very first being a few sentences, and revolving around a key question - looked at one of the most critical aspects of the "Climate Change" issue. (The word "Climate Change" is in quotes because it is not a good description of the real problem, but refers to one key ultimate affect of it, and confuses the issue.)
That aspect is the simple and almost always overlooked, or only trivially reported fact, that oceans ultimately drive climate; and our oceans are getting warmer.
This is because the level of so called greenhouse, or heat trapping, molecules in the atmosphere, is increasing. Greenhouse molecules capture and absorb infrared red radiation, and release it back outward in all directions. Most of the molecules in the air, predominantly the nitrogen and oxygen which make up almost our entire atmosphere, don't do this.
If our atmosphere was all nitrogen and oxygen, almost all heat given back off the earth's surface would instead escape back into space rather than being, at least in part, captured and re radiated. (With some of it being re radiated back downward.) And, as a result, the earth would essentially be a large ball of frozen rock and mainly ice, and about 0 degrees Fahrenheit on average, rather than the 59 or 60 degrees average (though rising) that it is; and life as we know it would not exist.
The ocean is constantly giving off heat or absorbing it. Just run a warm bath in a cold bathroom, or a freezing bath in a very hot bathroom, shut the door, and then come back in later to get a feel on a micro scale for this affect. An average, standard bathtub filled to the overflow valve contains about 45 gallons, or under one third of one cubic yard of water. The world's oceans contain about 1,750,000,000,000,000,000 cubic yards of water.
Since the world is also much larger than a bathroom (but much smaller in land surface size in comparison to ocean surface size, so imagine a bathroom where most of it is the bathtub, and the closed door experiment affect becomes greater still), the process is also far far slower, and far far more stable. Hence why over time, given the normal amount of sunlight emitted towards earth by the sun, oceans ultimately drive climate.
And, as the link above helps show, as more radiated heat is re-radiated by increasing concentrations of greenhouse gases in our atmosphere, warming the molecules all around rather than simply passing unfettered straight back out to space, our oceans are, slowly, getting warmer. And, very slowly, our climate, is starting to change, as a result.
But what about water in the air above? This is an issue that can be very confusing. And it is often incorrectly, if genuinely, used to postulate scientific misconceptions about the issue of radical long term atmospheric change.
The main idea, and it is very convincing sounding, is that by far and away the most important greenhouse gas is water vapor.
This is true if by "important," one means at any one single point in time, rather than over time. This is because at any one single point in time, water vapor, is responsible for more heat trapping re-radiation than any other greenhouse gas. (In fact, it is believed to be responsible for more than all of the others combined.)
And it is because, over time, water vapor, which forms as a result of weather, and ultimately, what shapes weather - our climate - is a response or affect of what we still call "Climate Change," rather than a driver of it.
So the often heard assertion that "Climate Change greenhouse gases don't really matter that much because water vapor is the most important greenhouse gas," is meaningless. And, even if inadvertently, pretty misleading as well. And certainly, highly incorrect
Long lived atmospheric greenhouse gases, over days, years, and centuries, re radiate heat that would otherwise be lost to space. And more of them in the atmosphere means more heat is re radiated rather than lost straight back to space. This has a number of key affects that drive things that ultimately become part of climate, or that in turn drive climate directly.
One of them is the evaporation of water from earth's surface and retention of that water, as water vapor and water droplets, in the atmosphere. The warmer the ambient air temperature the more water water it is capable of holding.
So, since more water vapor can be both created, and retained by the atmosphere at any period in time (and with increased average heat, there is increased energy) - we would think but can't be sure that over time this would lead to more "violent" or "intense" storms and precipitation events. (Violent and intense from our perspective, that is). And more precipitation volatility, or at least change from the present patterns, since the air is capable of receiving and holding more water, it may hold it longer, and or release more, and every combination thereof.
Another, related possibility and expected likelihood is of course just on average more water vapor overall. Since there is so much water vapor to begin with - and due to this large amount, it is such an important greenhouse component at any one point in time - this would lead to a fairly positive, or self reinforcing, feedback loop: One where increased overall atmospheric water vapor would then over time contribute even further to the atmospheric heat re radiation that is driving it in the first place.
To what affect this would take place, if any (or even to what it affect it is already starting to, if any), is unclear. Water vapor also increases the total albedo, or reflectivity, of the earth; which up in the air reflects more heat directly back out into space without it penetrating the atmosphere down to the surface.
In other words, cloud cover blocks the sun. So it is a little cooler. But, particularly if you are away from the city, notice the general difference between day and night time temperatures when the night is clear and the milky way visible, versus when it is dark and completely starless (water vapor enhanced). It is much warmer in the second instance, and far less heat (or energy) is escaping the earth/atmosphere system.
Sometimes on very cloudy days, that persist into full over night coverage, the temperature in the evening barely goes down from what it was in the day. All of the heat that is being giving off by the surface of the earth (land and water) and the objects on it, is having a hard time escaping through the atmosphere due to the greenhouse affect of all of that water vapor; so much of it gets re radiated back downward, and surface temperatures feel much warmer.
During a cloudy day this same heat trapping phenomenon that takes place at night is taking place under cloud cover as well, but some of the initial sunlight is being blocked, up in the atmosphere as well.
What the net overall affect of more long lived greenhouse gases, upon total average water vapor, and then that water vapor's net affect on weather, and over time, climate, is or will be is unclear. Clouds block some sunlight, but the same water vapor traps back a lot of the heat being thermally radiated off of the earth's land and sea masses, particularly at night.
What is completely clear, is that this key, if multi directional, aspect of the very short lived greenhouse molecule, has nothing to do with the issue of changing long lived lived atmospheric greenhouse gas concentrations, and does not drive or cause climate change, but is a reflection of it. One that would further enhance any affect by more greenhouse molecule trapping, and diminish it due to increased atmospheric albedo, or reflection.
Separately, the increased volatility likely to arise by an overall increase in atmospheric and earth/atmosphere energy over time along with the increased capacity of the atmosphere to evaporate, and absorb, larger amounts of water, is, from our perspective, a bad thing. This is because our land and river structures, and the plants on which we rely, evolved under certain general patterns. If the patterns were different, our river beds and pathways would be different,and able to accomdate those patterns without massive upheaval to current river beds, flood plains vegetation, etc.
So as precipitation patterns quickly change relative to geologic time, there is more run off and flooding, more water lost during large downpours, by root systems not designed for such intensity followed by periods of paucity, and possibly - though this seems to stand to reason from increased overall energy, it is less clear - higher intensity (for example wind, and wind like events) and thus more powerful and damaging, storm like events.
And it is probably not coincidental that many of the record rainfall and flooding events occurring over the past half century to century to more (depending on where) going back to the beginning of decent record keeping, have been somewhat concentrated, and, very loosely, increasing so, in ourmuch more recent time period, rather than being, say, evenly scattered throughout it, as a whole.
This is likely to continue, and greatly exacerbate: probably, in combination with overall changes in average ambient heat levels, to the point of "stunning" people. Many of whom then later are probably going to blame it on acts of God (which, in one sense, everything is anyway, but if we have free will, it is also acts from us, with God just giving us the tools and, we hope, pointing direction), or, ironically and genuinely, say, "wo, non one knew it would be like this," or "wow, no one saw this coming."
Of course some of them, our kids - maybe their kids - will also say, and quite appropriately, "WTF." Meaning, "How did this happen when the basics of the issue were incontrovertible, or quite easily predictable?"
What seems somewhat likely, but really isn't as predictable, is whether there will be somewhat of an additional compounding affect from increased average water vapor. Perhaps small, but who knows. Less likely is the diminishing affect first casually predicted years ago based on the simple observation that "water vapor is also cloud or cloud like cover, and this cools the earth." Since it will be heating the earth at the same time. Albeit clearly not as much during the day, but, at night exclusively; reigning in surface land and water cooling, and over time, net energy dissipation back out to space.
The real experiment, with no controls, and a big lag between cause and affect, is not what will generally happen as time goes forward - change the physical energy balance of the earth to a geologically radical degree, and things will radically change - but what will happen exactly. And happen, in conjunction with all the other, though far more subtler, slower, and often orders of magnitude less significant, random ongoing events of micro geologic time, and their shape upo the climate.
In other words, if we had 15 earths total - ours and 14 sister earths with identical conditions as ours, but for the radical change in long lived atmospheric greenhouse gases, what would happen over the next several hundred years, on the other 14?
That difference we will never know. What we will know is the ultimate affect on ours, with the radical changes being imparted. Right now, the essence of what that will be is the affect upon several processes, and systems, of increased atmospheric thermal re radiation back all around instead of allowing it to pass directly through back to space.
One of the more interesting, though less comfortably predictable aspects, is the affect of future water vapor, upon this process. Given that this is, after all, water, it might be appropriate to say that the overall amplifying or diminishing affect might well wind up being (hopefully), a wash. Or even even split between conflicting affects. (My hunch is it won't,. Since while both processes are going on during the day - even if in daylight hours the edge seems to go to the cooling affect, only one of the processes, the further greenhouse impact - and since at any one time water vapor makes up the majority of the atmospheric greenhouse affect, it is a large one - is going on at night.)
What is key to understand though is that the power of either such affect, is only relevant to the degree water vapor is influenced in the first place; and thus overall temperature, for example, changes. Thus it can only affect this process a fraction, at most. (thought it could be a big fraction.) And since we know it has two significant, if not perfectly counter balancing, affects that work in opposite directions, the overall ultimate net affect, can only be a fraction of this.
Though, notice that a lot of science sites I think incorrectly postulate ideas such as "possible runaway greenhouse affect," or a possible cooling period as a result of an extremely large increase in net long lived atmospheric green house gases due to the increase of water vapor: both of which are fairly far fetched - and particularly the latter one - for the reasons just given.
They both look far too much at one affect in isolation. But particularly the latter, which is heavily off base, as it doesn't seem to correctly take into account that it is only the increase in heat which would drive more water vapor in the first place; so any net cooling affect would not be increasing that heat in the first place. Or seem to legitimately account for the first affect of this same "cooling" cloud cover, which is that it simultaneously increases heat re radiation.
Thus the speculation that the total net affect of increased water vapor might be a slight dampening of total retained heat if water vapor did not also increase the earth's total collective albedo, is reasonable, if only speculation. But the idea that it would have an offsetting affect sufficient to cause net cooling in total as a result, is scientifically illogical.
(The idea that climate change could somehow produce radical cooling for a while, however, and further throwing anti climate change proponents into a tizzy of confusion that comes out as anti climate change accusation, may not be entirely illogical, and for completely different reasons, but is probably unlikely. But the idea that it would produce net cooling over the long run, is also, though not as bad as the structurally problematic "increased cloud cover from ambient warming will really cause ambient cooling" tautology, also somewhat scientifically far fetched. Earth's climate is ultimately driven by energy. Heat is energy. Increase that in the long run, by amounts that are geologically significant, and though ocean currents could change to produce strange shorter term affects or even massive ice build up, in the long run, more energy means more heat.)
While the net affect of increased water vapor might be positive (that is, it reinforces what is causing it in the first place, or increased heat re radiation leading to a greater earth atmosphere energy balance leading to higher overall temperatures), the fact that at at least could be slightly dampening, is good, since, for very specific reasons, almost all affects of a radical heat retention change to the atmosphere are self reinforcing. (For example, frozen ice melts under warmer conditions, and the surface shifts from a very high albedo, to one of the lowest on earth - open water, or one that is still very low - tundra; melting polar ice fails to keep the northern waters as cool as they would be (in turn leading to more melting) which then fails to cool the ocean's streams as they pass through, thus dropping down and cooling (or in this case, not) the mid and lower latitudes; melting permafrost releases enormous quantities of carbon in the form of carbon dioxide, and methane, which further increase the amount of heat energy that is absorbed and re radiated outward and thus prevented from escaping into space, leading to even more melting, until a new stases, or point of "relative" stability, is reached; etc.)
In short, water vapor is a really interesting part of this equation. And a problematic one when it comes to the separate issue of increased energy, and thus precipitation pattern and intensity variability. But, since it's a result rather than a cause, and as a result then in turn has both ameliorating and exacerbating affects, it's probably not the key one. Polar ice caps, sea ice, and the related, but also separate, issue of total earth surface albedo, and ocean changes, all of which are not partially self canceling, but self reinforcing, are dominant. And why the overall "Climate Change" issue is not remotely about "change the air a small amount, and it warms up a small amount."
That change in the air may seem a small amount to us. But it's a huge amount in geologic terms. And in geologic terms, the stabilizing conditions as they presently exist - polar ice, sea ice, permafrost, and retained ocean energy (heat) - with such increased inputs of energy, would have no reason in physics, to stay in the general range of conditions in which they presently exist, and under which we evolved. And physics, ultimately, is the only thing drives this issue.
Not - despite all the ''hot air" coming out - shouting, rhetoric, belief, perception, earth's desires, misinformation, or politics. All of this can, and, in a profound ways, does have an impact, because it impacts how we respond (or not respond) to this challenge. And since it is us causing this change to our world, how we respond to alter or offset what is causing it, or don't, will, ultimately, shape our future.
But it has nothing to do with what is going on in the first place, in order to then assess to what degree, and how to, respond. That, shouting aside, is pure physics. And it doesn't change, with good arguments, or simple expectations that the earth "can not" change so radically, because most of the time, "things don't change so radically," and that (even if for good evolutionary reasons) we have an evolved expectation of relative "sameness" built in to our perceptions.
Because, number one, it's only radical to us. And number two - and the fundamental point that is repeatedly being missed about the "Climate Change" issue - is that the change that has occurred, and that is still occurring, at very fast speed, to the long term heat trapping composition of our atmosphere, geologically speaking, and in relation to what we evolved under (again, in relation to us), is, radical.
Update 8-18-14: A study published in the Proceedings of the National Academies of Science concluded that water vapor is a positive warming feedback:
We use a set of coordinated model experiments to confirm that the satellite-observed increase in upper-tropospheric water vapor over the last three decades is primarily attributable to human activities. This attribution has significant implications for climate sciences because it corroborates the presence of the largest positive feedback in the climate system.
Although, as a later article on this site points out, at least one scientist argued - even getting a paper published before the editor resigned due to the level of mistake - that even though water vapor, ephemeral and always changing, is clearly a feedback, or result, not a forcing agent, or driver, of longer term climate, it was nevertheless a driver of the more basic changes we've observed and not an altering or reinforcing response, to them. (This, although greatly simplified, is somewhat like arguing that later symptoms/vitality in response to eating spoiled/excellent food earlier, was the driver of feeling ill/energetic, rather than a response to it. It also seems like far more than an otherwise somewhat "remarkable coincidence" that t his same scientist, also just happens to be a well known and rare skeptic of the idea of AGW significance.)