So now the big one water vapour, water is a unique and special substance, it is the only substance that reduces in volume when changing froma solid to a liquid, it has an extremely high specific heat content, while it is a GHG, the proposed theory that an increase in water vapour will produce an increase in heat, which would again cause an increase in water vapour, is just pure scientific bunkum, the world would've spiralled into Venus like temperature long ago if that was true, anyway examination of temperature and water vapour charts, does show that water vapour does increase with temperature but also drops rapidly as well, the 1997/98 El Nino spike shows that very well.
So although it has some postive effects, it also has numerous negative effects, it drives the water cycle (which is a heat engine) that cools Earths surface, as temperatures go up, the engine works stronger and faster maintaining stable temperatures, it also effects our atmospheric adiabatic lapse rate, moist lapse rate is about 5.5C per Km height, whereas dry lapse rate is almost double at 10C Km, this is a cooling effect, by pushing temperatures higher up, increasing the height of the tropopause and radiating a lot more heat to space.
It is a known fact that ocean SST's never exceed 30/31C many scientists put this down to water vapour acting as a thermostat by increasing evaporation, SKS tries very hard to debunk this and pours doubt on some of the theories, however I note they have no explanation of why SST's do not exceed 30/31C.
I believe that water vapour not so much acts as a thermostat, but more of a limiter (like an engine rev limiter) preventing temperatures from ever getting too hot.
Sorry that I can't explain the technical details but I do have one example of a negative feedback. If the surface temperature warms, there is increased evaporation over the oceans which leads to an increase in cloud cover. This results in a lowered albedo do to reflected sun energy which leads to cooling.
However, I am like you and don't understand all processes. Having said that, I do not believe climate science has a full grasp on all climate processes of which cloud effects are one. So even in my negative feedback example, there could be other processes at work. If a process doesn't work exactly as expected, that means there is something else unknown which is a factor.
I guess what I'm saying is the basis of my skepticism with which I'm sure you are familiar is that I feel climate science has overstated their certainty of their overall body of knowledge.
Ahh you are starting to open your mind.
Let's talk about the Earth and the balance of feedbacks. The Earth has been around for about 4.5 billion years. During at least the last 1 billion years, in order for life to evolve on this planet, the Earth had to have a relatively stable climate. If at any point it would have gone to a Mars-like environment OR a Venus-like environment, all life would have ended and we would simply not be here.
Now what the warmers are proposing and why I STRONGLY disagree with them, is a climate that is NOT stable, but ruled by positive feedbacks, not negative feedbacks.
Here is a simple exercise, pull up excel. In A1 place 0, then in A2 place "=A2+NORMINV(RAND(),0,10)".
Now simply copy that A2 Down say 1000 or 10,000. This is called a random walk. Note that you are adding to 0 a random variable that has a mean of 0, so it should stay right around 0, but it does not even closely stay around zero.
This represents NO positive or negative feedbacks yet you can see how unstable it is, IF you dared to do this simple exercise.
So we already KNOW the earth must be more stable. It is not really a question of whether there are more negative feedbacks at work, because we are alive, and evolution has had enough time to work.
BUT you are right. There are a number of positive feedbacks, including albedo, methane, etc. BUT, the OCEANS ARE VAST!!!!! IF you wish to do another calculation, just try to figure out the amount of energy required to raise the temperature of the entirety of the oceans by 1 degree.
Let me help. The oceans and seas are ~1.5 billion km^3, thats 1.5*10^18 m^3 or 1.5 * 10^24 dm^3, or 1.5 *10^24 Kcal. Or 6.276 *10^24 KJoules.
This si just the energy required to raise the oceans 1 degree. Add to that the energy exchange when you oncrease the temps of the oceans. You see, if you increase the temps of the oceans, then more evaporation occurs which decreases the temps.
Once again, I am NOT agianst reducing our CO2 output. I think we should. BUT we have already resorted to stupid policies that have us using 4.9 billion bushel of corn a year for ethanol production. Million of people a year die in third world countries from respiratory problems caused by burning dung to heat their homes as they have no electricity.
We are literally pretending the probelm is worse than it really is, while ignoring the consequences of taking the wrong actions. The Earth is amazing at healing itself. I have seen rivers and lakes come back from being extremely polluted in a matter of 10-15 years. Why? Negative feedbacks.
So YES we shoudl work to reduce our CO2 production, BUT we are not talking about impending doom, so our solutions need to be less damaging to society than the problems.
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I will say this. Antarcticice places some possibly defensible numbers in that scientists think they kind of know what is going on. Here is the problem... They don't know crap. Its not their fault. They are studying a very complex system that they cannot test. All they can do is create models using past information.
Here is the problem. In the past, CO2 was entirely naturally controlled. So when you look at the past, temp increases raised CO2 concs and CO2 concs raised temps. SO when looking at the effect in the past, we cannot separate CO2 from temp raises (or the cause and effect).
When artificially adding CO2 to the atmosphere, though, We are adding it, not the temp increases.
So consider: If temps cause an increase in CO2 conc, BUT CO2 conc did not cause an increase in temps, then our adding CO2 would have a 0% change as what we would estimate from the past.
If CO2 caused temps change, but temp changes did not add CO2 then our adding CO2 would have a 100% change as what we would estimate from the past.
We are somewhere in between. Our being somewhere in between, is why >95% of the model are overestimating AND many of our climate scientists are think the positive feedbacks must be stronger than they really are.
And while people like Antice, can throw around numbers and seem correct, the history of the earth is a long history of climate ruled by NEGATIVE feedbacks, not positive.
Overall, Nature is generally a stable system, so I would expect there to be negative feedbacks that moderate the warming rather than a positive feedback that amplifies the 1.2C warming that basic physics says we should expect from a doubling of CO2 levels. I do not know the details, but based on what we see in the rest of Nature I would expect more negative feedbacks than positive.
Cloud feedbacks are potentially so substantial that they overwhelm the warming produced by CO2. In models, scientists are assuming a positive feedback from clouds. This uncertainty is mentioned in the IPCC report, but not the implications that the overall effect of global warming could be negligible.
One negative feedback is the Stefan Boltzmann law. Basically a warmer planet will emit more heat to space, because it is warmer.
Another negative feedback is plants absorbing more CO2. Oceans absorbing heat from the atmosphere is another.
Aerosols also have a cooling effect, but they are not considered a negative feedback since they are not produced by the warming. If volcanic eruptions were discovered to be caused by global warming, then that would make the aerosols emitted by the eruptions another negative feedback. I suppose you could argue that more warming means more AC, which produces more aerosols, but that effect is negligible.
The hotter the Earth gets, the more heat it radiates back into space, and this increases exponentially. This is why the Equator's temperature never changes much - it was only 2 degrees colder at the Equator during the last major ice age. The farther North or South you go, the colder it is to start with, thus you get more temperature swings in either direction.
The only one I can think of off the top of my head is temps, plant growth and CO2.
Higher temps promote plant growth (in general) which absorbs more CO2.
In reverse, lower temps (and bigger ice caps) increase CO2 as plant decay exceeds growth.
Can't recall the others, but there clearly are some, because Earth is not Mars or Venus.
The rub is in the time scale. The natural feedbacks tend to take thousands or tens of thousands of years. AGW dwarfs those effects because it is happening on a scale of decades or centuries. Time scale, like percentages, trend-vs-variation, etc. is difficult for many "skeptics" to grasp. They can handle Flintstones riding dinosaurs, but not high school science.
Since I am not a practicing alarmists, I have a hard time motivating myself to learning all the intricacies of your belief system. Obviously there are negative feedbacks too or we would have had run away warming every interglacial and obviously before that when it was even warmer. I was going to say something on the lines of Ottawa Mike but he said it better than I would have.
Clouds could be, depending on whether they are ice or water, high or low, or at night or daytime. They are very important, but we just do not know. An interviewee in Science News was leaning toward positive feedback, but said we really don't know.
The biggest negative feedback is temperature itself. The amount of energy a body radiates to space is proportional to the 4th power of absolute temperature. Since the amount of extra energy retained is proportional to the log of greenhouse gas concentration, this is extremely powerful feedback.
If global warming actually caused more hurricanes, that would be a negative feedback. And, given that the sea ice expansion around Antarctica could be caused by meltwater diluting seawater, that would be a negative feedback.
Negative feedbacks, if they were a factor, should not be expected to result if nice weather. Negative feedback tends to cause overshoot. This would result in events of extreme heat and extreme cold. I am not saying that global warming causes cold weather, but, if it did, negative feedbacks would be the mechanism.
http://en.wikipedia.org/wiki/Overshoot_%...
Earth being not to hot or cold for life is not evidence of negative feedbacks or evidence against positive feedbacks. Earth has been habitable for hundreds of millions of years because the Sun is stable. And if not for positive feedbacks, slight changes in Earth's orbit and axial tilt would not result in ice ages.
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Cloud cover is a positive feedback.
http://www.climate4you.com/images/CloudC...
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Besides methane, melting permafrost also releases hydrogen sulfide, which reacts with oxygen and water to form aerosols. The methane seems to win, but the aerosols which come from the hydrogen sulfide probably reduces the effect on the trend, but could cause extreme weather events.
My understanding has always been that there are a number of strong positive feedbacks; water vapour, ice and snow albedo, etc, and that in a warming world, these will tend to cause further warming.
But when it comes to negative feedbacks, which would tend to reduce any warming, there seems to be much less in the way of these. So the balance of feedbacks (climate sensitivity) is considered to be positive, likely strongly positive.
Not everyone agrees with this though, I often see claims of strong negative feedbacks, meaning that climate sensitivity is low and therefore increasing CO2 is not a problem.
Now, I have to admit, I am sceptical of this view given the potential positive feedbacks, but I have to own up to a certain amount of ignorance on the subject too, especially when it comes to negative feedbacks.
So what can you tell me about negative feedbacks?
What significant negative feedbacks are there?
And how strong are they; how much can they offset the positive feedbacks?
Kano seems to be telling you porkies he claim sea ice is expanding, but the planet has two main sea ice fields one is expanding (Antarctica) at a rate of ~1% per decade, the other is the Antarctic which is shrinking at a rate of ~10% per decade (you do the math)
Sea water is a strong absorber of the Sun's energy i.e. albedo compared to snow covered ice, kano also neglects to mention that Antarctic sea ice, melts almost entirely each summer but traditionally Arctic sea ice only thinned, which is why areas like the North West Passage are now starting to open up, people looked (quite hard) for ways through this region for centuries and very occasionally (in just the last 100 years) a very few made it through in strengthened ships or taking months or even years to get through, now it has been possible to sail straight through (only in the last few years)
As for figures quoted on the thousands of years it would take for Antarctica and Greenland glacial ice to melt, this is true, but then groups like the IPCC are quoting sea level rise in the range 1-2m or in the higher ranges 3-5m. A rise of 1-2m needs only 1-2% of Antarctica and Greenland to melt and that can happen in a lot less than thousands of years. If a total melt was being estimated then the number mentioned would be more like 70-75m, but deniers do seem to like pretending a total melt has been predicted, it hasn't, certainly not by the end of this century.
One negative feedback seems to be that very growth of Antarctic sea ice, deniers like to try and play up, even as these same deniers ignore the cause, melting glacial water from Antarctica, which is fresh water, instead of salt water, it is lowering the salinity of the waters around Antarctica. Deniers like to claim nobody predicted this, but going back to the early 1990's a number of scientists suggested this could be a short term effect as glacial ice finds it way into the sea as melt water. Of course in this context "short term" may be decades rather than the usual denier time from of a few weeks or just next Winter.
Another negative feedback is volcanic eruption, but it's cause is not linked to climate change and we have no current way to predict eruptions, Pinatubo cause a short term drop of ~0.5c. If we had something much larger occur then the effect would be more pronounced or a string of Pinatubo like eruptions. Such string of eruptions is thought to have contributed to the little ice age. in roughly the middle of this event was the Year Without Summer caused by the eruption of Mount Tambora in 1815 but also aided by the eruptions of -
1812, La Soufrière on Saint Vincent in the Caribbean
1812, Awu in the Sangihe Islands, Indonesia
1813, Suwanosejima in the Ryukyu Islands, Japan
1814, Mayon in the Philippines
Oddly while deniers keep trying to insist a rise of 1c (0.8c) is "nothing" the effects seen in the Year Without Summer are thought to have only caused a drop of ~0.7c below the then mean, yet this was enough to cause crop failure and famine. It is also thought to be linked to millions of deaths across Europe due to respiratory illness, on a level with a medium level plague event.
The earlier set of Volcanoes where all VEI 4 or higher, Tambora was a VEI 7.
So a massive volcanic event would certainly be a strong negative feedback, but something like an eruption of a super volcano would certainly also be a case of the cure being far far worse than the disease, as such events are also linked to mass extinction events.
Basic cause and effect here is particulates, in an event like Tambora (or Pinatubo) the effect lasts ~15-18 months but a string of effect cause a longer term effect as ice field grow as does sea ice also affecting albedo. Which stretches out the effect even longer.
Crocoduck: Not quite, water vapor is the primary greenhouse gas and it lowers as you move away from the equator, a rise in water vapor is linked to the much higher rise in temp seen at the poles, while the global average rise is ~1c, the Arctic has seen a rise of more like 3-5c
