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Atmospheric CO2 has gone up 20% since 1960

lomiller said:
the problem is that you don’t know the difference between closed and open loop properties and haven’t bothered to try and see if the math backs up your assumptions.

For a positive feedback loop (lti or within a range that can be approximated as lti) the response to a change in input is:

Ochange = ichange * [a/(1-a*b)]
where a is the open loop gain and b is the feedback factor

this is a well documented formula that can be found in any introductory textbook on system theory.

In your example you erroneously base the effect of co2 on the system input rather then the system output. It’s a feedback element which means it samples the system output and adds/subtracts to the system input based on it. This is what it should look like drawn out properly.

- insolation (a) goes up from 100 w to 101 w which creates a 1w energy imbalance
- the forward gain is 1deg/w giving a 1 deg increase in t
- the increase in t releases enough co2 to reduce outgoing energy by 0.5w creating it’s own 0.5w imbalance
- this causes a further 0.5 deg of warming, which releases more co2, which causes another 0.25w imbalance.
- etc etc

each iteration of the loop adds a term to the series that represents the final change in t

t = tstart + 1 + 0.5 + 0.25 + 0.125 + …

you can work it out by hand or computer to find out that the series converges to an increase of 2 deg. Alternatively you can use the formula i gave above.

Now reverse it
- insolation (a) goes up from 101 w to 100 w which creates a -1w energy imbalance
- the forward gain is 1deg/w giving a 1 deg decrease in t
- the decrease in t causes the absorption of enough co2 to increase outgoing energy by 0.5w creating it’s own -0.5w imbalance
- this causes a further 0.5 deg of cooling, which causes the absorption of more co2, which causes another -0.25w imbalance.
- etc etc
t = tstart – 1 – 0.5 – 0.25 – 0.125 -…

again the series converges to tstart – 2 deg.
Click to expand...

Good, we are on the same page!

The next problem is that my page says:

Start 100
Iteration 1) 100.502
Iteration 2) 101.007
Iteration 3) 101.515
Iteration 4) 102.025
Iteration 5) 102.538
Iteration 6) 103.053
Iteration 7) 103.571
Iteration 8) 104.092
Iteration 9) 104.615
Iteration 10) 105.140

This is in keeping with the result that positive feedback causes runaway.
Runaway can be prevented by limiting factors but hysteresis will remain.
The input will need to go below the starting point to effect a reversal.

Study the problem and see if you do not agree.
 
It just come to me in a flash, daylight saving. It's that extra hour of sunshine causing all the warming?
 
Old Bob said:
It just come to me in a flash, daylight saving. It's that extra hour of sunshine causing all the warming?
Click to expand...

Good thought!

And, that causes people to have more fires and grills OUTSIDE where it will make the outside warmer.

We should do away with DST and ask people to always cook inside the house so the heat won't get out and warm the Earth.
 
G O R T said:
Good, we are on the same page!

The next problem is that my page says:

Start 100
Iteration 1) 100.502
Iteration 2) 101.007
Iteration 3) 101.515
Iteration 4) 102.025
Iteration 5) 102.538
Iteration 6) 103.053
Iteration 7) 103.571
Iteration 8) 104.092
Iteration 9) 104.615
Iteration 10) 105.140

This is in keeping with the result that positive feedback causes runaway.
Runaway can be prevented by limiting factors but hysteresis will remain.
The input will need to go below the starting point to effect a reversal.

Study the problem and see if you do not agree.
Click to expand...

Lomiller's example seems to make sense, as much as my remembrance of control theory allows; I don't think that a constant positive feedback causes runaway.

An increasing feedback could, though.

Can you detail your calculations a bit more, like lomiller did? That might help.
 
G O R T said:
The next problem is that my page says:
.
Click to expand...


Then your doing it wrong. You should only be applying the feedback from the change in forcing resulting from the previous iteration, the rest is already fully resolved.

Basically you are still struggling with open vs closed loop.
 
I just like to look at the facts: The Arctic Ice cap is melting away. Why. If it is a natural non man made process, what exacly IS that process. Tell me. What are the OBSERVED - or even extrapolated -natural processes involved. What has changed to cause the ice to melt, pure and simple
 
And what will be the effect when the ice is gone in the Arctic? Seems to me it would be a catastrophic change since the Pacific Ocean will warm rapidly, just as water in a glass warms rapidly when the ice in it melts. Add to that the absorbed rather than reflected sunlight, and an increased atmospheric temp at sea level adding heat as well. And a warmer Pacific could be catastrophic because the result would be amped up weather systems that cross the US by the dozens every year. Consider how excessively tormented the jet stream "sine wave" is this moment, causing a stagnant low to linger for many many days in the South. And that was preceded by a long soaking of the East Coast due to stagnation. I expect more of what I call an amped up jet stream, where one side of the sine way is an amped up low and the other an amped up high, leading to extremes in ALL aspects of weather
 
Tumbleweed said:
And what will be the effect when the ice is gone in the Arctic? Seems to me it would be a catastrophic change since the Pacific Ocean will warm rapidly, just as water in a glass warms rapidly when the ice in it melts.
Click to expand...

I doubt this analogy is worth anything at all. The rapid warming in this case is only observed if the liquid phase is (near) perfectly mixed, with even temperatures. This clearly isn't the case.

McHrozni
 
You forget latent heat - the actual melting is pulling immense amounts of energy from the geo-sphere to melt the ice.
The air temp over melting ice fields varies hardly at all.
What do you thnk will happen when that turns to bare rock or tundra vegetation.

Once the ice is gone he energy will turn up in other forms, mostly temperature gains.

In addition there will be direct forcing via albedo particularly in the Arctic where it is open water.

The cryosphere is a huge damper on temperature swings in the atmosphere.

•••

101??....pot...kettle..:garfield: unimaginable :rolleyes:

•••

September 17, 2009 Future Geographies: Feedbacks Driving Global Warming

There are two types of feedbacks, positive feedbacks that drive system change and negative feedbacks that seek to keep systems in a state of equilibrium. Geoscientists like physical geographers are recognizing that positive feedback mechanisms may drive the Earth system past thresholds and towards a new state of equilibrium. In so doing, a new physical geography of the Earth system will appear. The
distribution of Earth’s regional climate’s and ecosystems may be irreversibly altered.
Click to expand...
Good article on the various feedbacks continues

http://tpeblog.wordpress.com/2009/09/17/future-geographies-feedbacks-driving-global-warming/

•••

Jet stream alterations...

http://tpeblog.wordpress.com/2008/04/17/shifting-jet-streams-is-it-global-warming/

and

http://www.ciw.edu/news/changing_jet_streams_may_alter_paths_storms_and_hurricanes
 
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Wangler said:
Lomiller's example seems to make sense, as much as my remembrance of control theory allows; I don't think that a constant positive feedback causes runaway.

An increasing feedback could, though.
Click to expand...


It’s gain dependent. The simplest criteria for stability is that A*B < 1, which in this case is met because there is no new energy added in A and B isn't very large.

For if you have an active system where there is forward gain that will almost always be unstable.
 
No :rolleyes:

••

3 decades of rapid change .....deniers nightmare.....stayed tuned....the commercial break is over...
http://www.guardian.co.uk/environment/2009/sep/16/ocean-temperature-el-nino-noaa

do keep the pointyhead down in the sand - it's good for that.....

Glacial Acceleration - A Sea of Troubles
By Paul Brown
Author of Global Warning: The Last Chance for Change

It is hard to shock journalists and at the same time leave them in awe of the power of nature. A group returning from a helicopter trip flying over, then landing on, the Greenland ice cap at the time of maximum ice melt last month were shaken. One shrugged and said:"It is too late already."

What they were all talking about was the moulins, not one moulin but hundreds, possibly thousands. "Moulin" is a word I had only just become familiar with. It is the name for a giant hole in a glacier through which millions of gallons of melt water cascade through to the rock below. The water has the effect of lubricating the glaciers so they move at three times the rate that they did previously.

Some of these moulins in Greenland are so big that they run on the scale of Niagra Falls. The scientists who accompanied these journalists on the trip were almost as alarmed. That is pretty significant because they are world experts on ice and Greenland in particular.

We were visiting Ilulissat, Greenland, once a stronghold of Innuit hunters but now with so little ice that the dog sleds are in danger of falling through even in the depth of winter.

But it is not the lack of sea ice that worries scientists and should be of serious concern to the inhabitants of coastal zones across the world. Cities like New York and states like Florida are in the front line.

Scientists know this already, but just to give you some idea of the problem, the Greenland ice cap is melting at such a fast rate it is triggering earthquakes as pieces of ice several cubic kilometres in size break up.

Scientists say the acceleration of melting and subsequent speeding up of giant glaciers could be catastrophic in terms of sea level rise and make previous predictions published this year by the Intergovernmental Panel on Climate Change (IPCC) far too low. The glacier at Ilulissat, which it is believed spawned the iceberg which sank the Titantic, is now flowing three times faster into the sea than it was 10 years ago.

Robert Correll, chairman of the Artic Climate Impact Assessment, from Washington told me:"We have seen a massive acceleration of the speed with which these glaciers are moving into the sea. The ice is moving at 2 metres an hour on a front five kilometres long and 1,500 metres deep. "That means that this one glacier puts enough fresh water into the sea in one day to provide drinking water for a city the size New York or London for a year."

Professor Correll, who is also director of the global change programme at the Heinz Centre in Washington said the estimates of sea level rise in the IPCC report in February had been "conservative" and based on data two years old. The range of rise this century had been predicted to be 20 to 60 centimetres, but would be the upper end of this range at a minimum and some now believed it could be two metres. This would have catastrophic effects for European and US coastlines.

He said newly invented ice penetrating radar showed that the melt water was pouring through to the bottom of the glacier creating a melt water lake 500 metres deep causing the glacier "to float on land. "These melt water rivers are lubricating the glacier, like applying oil to a surface and causing it to slide into the sea. It is causing a massive acceleration which could be catastrophic."

The glacier is now moving at 15 kilometres a year into the sea although in periodic surges it moves even faster. He has seen a surge, which he had measured as moving five kilometres in 90 minutes - an extraordinary event.
Click to expand...
more
http://www.buzzle.com/articles/glacial-acceleration-a-sea-of-troubles.html
 
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Quote:
September 17, 2009 Future Geographies: Feedbacks Driving Global Warming

There are two types of feedbacks, positive feedbacks that drive system change and negative feedbacks that seek to keep systems in a state of equilibrium. Geoscientists like physical geographers are recognizing that positive feedback mechanisms may drive the Earth system past thresholds and towards a new state of equilibrium. In so doing, a new physical geography of the Earth system will appear. The
distribution of Earth’s regional climate’s and ecosystems may be irreversibly altered.

Oh yeah I couldn't agree more with the above, thank you. I think of that experiment in chemistry lab where one liquid is dripped into a vial containing another until an equilibrium is reached. Then it takes only one more lousy drop to turn the clear solution pink. And so it could be with our climate: One more drop of whatever - such as CO2 or one more square mile of open water instead of ice - and bye bye equilibrium and hello new equilibrium
 
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