Thread: Stuck with feedback on global warming ?

Hi am quite new to this forum and hopefully my question wont sound silly , but I want to know if albedo is decreased and as a result of this water has increased and so has the gmst has increased what type of feedback this is?> I initially thought it is positive one as water increases as a result of albedo decrease and so does the global temperature , but now I am convinced it is negative as we look what we decreased initially which is the albedo hence there wasn't further decrease of albedo instead there was an increase of global temperature which is a negative feedback ? please someone explain

I initially thought it is positive one as water increases as a result of albedo decrease and so does the global temperature , but now I am convinced it is negative as we look what we decreased initially which is the albedo hence there wasn't further decrease of albedo

The steps (in our current climate) work along the lines of

1. warmer temperatures of oceans and atmosphere reduce ice cover on oceans in summer and shorten the season of snow cover on land. Both of these reduce albedo and increase warming of both soil and water.

2. This increases local temperatures and, at some time, atmospheric temperature.

3. Increased atmospheric temperature increases the amount of water vapour the atmosphere can hold. (6-7% per degree celsius of temp rise)

4. H20 is a much more effective greenhouse gas than CO2, so once you increase the atmosphere's capacity to hold water vapour, the warmer it will get even though water precipitates out of the atmosphere quite quickly.

This item is a good start. Explaining how the water vapor greenhouse effect works

thank you so much but I still dont have an answer to my question is the above i described positive or negative feedback , i now thing it is negative what do you think ?

Not sure what you think positive and negative feedback mean for these purposes.

The way I explain it is that CO2 is a warming forcing on climate systems. There are consequences.

One consequence is loss of albedo and that becomes a positive feedback increasing the warming tendency of the original forcing.

Another consequence is increased water vapour in the atmosphere. That is also a positive feedback.

The only doubts about positive/negative feedbacks at this simple level is water vapour that aggregates into clouds. Low clouds and clouds high in the atmosphere have different effects, one lot enhances warming, the other suppresses it. There's a fair bit of work being done on this, but the cautious consensus at the moment is that the net effect is in the warming direction rather than the cooling. The bigger problem is knowing whether or not further warming will change the balance of low/high clouds in any significant way globally and therefore the net global warming or cooling effects.

now I got even more confused , isnt it when the albedo is decreased and as a result of it the h2o increases so does the gmst ,so isnt this negative feedback , because it is affected in the opposite direction ?

Feedback of what in relation to what?

If we're talking GAT, then a rise, warming, leads to less albedo.

Less albedo leads to more warming - which is in the same direction as the initial forcing - so that's positive feedback.

Positive feedback reinforces or strengthens an initial forcing. Negative feedback weakens or counteracts a forcing.

Climate feedback mechanisms are significantly more complex than the extant climate models.

Cohen, Barlow and Saito published a paper in the Journal of Climate volumn 22 in 2009 about how the interplay between the troposphere and stratosphere is cooling late boreal winters.

roughly
low albedo means high evaporation means more clouds means high albedo means more precipitation, which in boreal winters means more snowcover means high albedo means colder temperatures

This part of Iowa had the coldest first 3 months (Jan., Feb., March)on record this year(2013). This whole year(so far)in Iowa has been much cooler than normal.
In contrast to the planet having a very warm 2012.

So, warming causes cooling-----------------------------crazy enough?

It gets better--------------

I have described it above , here it is again , if you were able to lets say flick a switch and decrease the albedo , and obviously the global temperature will increase what feedback is this , surely if it is positive feedback the global temperature will decrease as a result of the decrease of albedo but instead it increases (which is obviously what is expected to happen ) , but from what I understand when one factor is decreased or increased to be a positive feedback the change of the global temperature would go in the same direction as the factor change ,so basic example if a factor is increased and the global temperature increases as a result this is positive feedback , but if it is negative feedback when one factor is decreased and the temperature goes in the opposite direction ? hope you understand now what i am asking

You seem to be confusing reactions with climate feedback mechanisms.

if you were able to lets say flick a switch and decrease the albedo , and obviously the global temperature will increase what feedback is this

this is a reaction to your lowering of albedo.

lower albedo = more solar warming of land surfaces.

the feedback mechanisms would involve how the climate reacts to your action of flicking that switch
and that depends on all of the current climate forcing mechanisms including biomass growth, solar activity, concentrations of atmospheric gasses, height of tropopause, milankovitch cycles, etc.............etc........

I get it but what I have been asked is simply this ? and I am all confused for the same reasons , I must say however I am new and climate is not what i want to really study but it is part of my course ; ( , so I studied about example of two tanks of water basically describing negative and positive feedback , in the first example there was a tank with constant input of water and by adding extra water to the tank but letting it out at a faster rate the tank went back to a balanced state ie the water decreased to near original level , this is said to be negative feedback , in the second case the tank there is also the same amount of water and constant input and added water but it is let out slower and so it overflows the tank this is the positive feedback so here it is when compared the above isnt this negative feedback ? I originally thought it is positive as decreasing albedo led to increase of water and as a result of the water increase the temperature increase ie the same direction of the water , but after looking again they actually asking for the original change we made so in this case the extra water is the albedo change so the result is temperature increase which is opposite direction just like in the example of the negative feedback example ? I am sorry if I am confusing you but this is what I am looking at not what it depends on just this isolated situation

ps and compare it with the water cycle

Well, a lot of people use the tap running into a bath and changing the flow rate out of it analogy to talk about the accumulation or otherwise of CO2. I've not heard of using the same approach to albedo. And I don't think it works so well - as an analogy. An analogy is supposed to make the logic clearer, you have to do a bit of twisting and turning to make it work.

The first step in your logical process is to decide what you're actually focusing on as being the 'thing' that is enhanced or counteracted.

Number one. Temperature.

The steps are ...
1. Temperature increases, which then
2. Causes loss of albedo, which then
3. Causes temperature to rise further, which then
4. Causes further loss of albedo.

This process is a positive feedback in warming. It will only stop when there is no more snow cover on land or ice cover on ocean to melt.

Number two. Albedo

1. Albedo decreases, which then
2. Causes temperatures to rise, which then
3. Causes further loss of albedo, which then
4. Causes further rise in temperatures .....

So this way you have positive feedback to the process of loss of albedo.

Both of these ways turn out to be positive feedback.

A question. Are you getting tangled up with a question that frames a loss of something as being a "positive" feedback?

Remember if CO2 were decreasing rather than increasing in the atmosphere, a process of decreasing temperatures would begin. The lower the temperature, the less water vapour the atmosphere can hold so the temperature will decline further. Which will lead to less atmospheric moisture, lower temperature .... and so on. This self reinforcing cycle of temperatures declining is also a positive feedback process. The "positive" description applies to whether the consequence pushes the process further in a particular direction, not to the direction itself. The fact that we describe these things in terms of up or down, or as increasing or decreasing, isn't relevant. But it can make it harder to think them through.

If this still causes you trouble, think of driving a car in reverse gear and then increasing the speed. You're accelerating - but you're going backwards.

this is what I actually had written first in my answer , after which I read the question to my sister who is in no way scientist she changed the way i look at it ,hence she said well albedo is decreased so the opposite direction happens the temperature increase as where I was stating that by decreasing the albedo the temperature will rise the water will increase the albedo will decrease further and so it will be positive feedback . so I was right in my original statement ?

Sounds like it.

Maybe your sister is the one who's misleading herself mixing up increase/decrease of various measurements with positive/negative feedback of one (or several) processes.

I must say however I am new and climate is not what i want to really study but it is part of my course

\

Seems to be at the heart of your confusion.

thank you all so much I think it really is quite clear now . Sculptor I think we all have points like these but global warming isnt really part of my medicine and cells interest , however there are parts in the book which are quite interesting , but really the truth is I didnt like it that much because I feel it isnt explained the way Adelady has explained it ,so clear and easy to understand thanks again , I am sure I will be asking some questions again , you guys/ladies are so helpful