Naked Science Forum
Life Sciences => The Environment => Topic started by: davidjuliowang on 17/05/2006 05:07:13
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30 Degrees On Vancouver Island
It's May.
It's Spring.
It's been 30 Degrees Celsius for the past two days in a row and it will be so until Saturday.
The normal temperatures for this time are 15-18 degrees celsius.
Vancouver Island is an island.
Nanaimo is right on the water.
It should be cooler.
I don't want to think what it's like on the mainland, or especially in downtown Vancouver.
Construction
I work in construction.
It was sickeningly hot out.
Working in construction is taxing for me.
The site is still unpaved dirt and with the heat and the wind the dirt forms little clouds of choking dust.
A hose was used to wet the dirt to keep the dust from choking everyone.
The hose had a huge leak with water spilling out everywhere.
Did I say anything?
No.
Why?
I don't want to jeopardize my job, but...you know...I should have.
It's important for my coworkers to see that someone is aware that water is not an unlimited resource, and that wasting it is a sad act.
Speaking of waste: the construction industry is far too, far too wasteful.
Collecting garbage is a taxing activity for me.
So much plastic and paper and metal and styrofoam all thrown into one big bin destined to be buried and forgotten : a testimony to humanity's still as of yet unexamined belief in the unlimitedness of our resources.
It saddens me to a degree that almost distracts me from my work (but I hold on because work = money = survival).
I have a plan to tell my boss about a service which sets up bins to separate recyclables and insure that they are recycled, but I'm reticent because I don't think he'll go for it.
Don't worry though.
I will try regardless.
World Is On Fire : Sarah McLachlan
If you like a song with a message may I recommend Sarah McLachlan's.
She's a wonderful Canadian singer with a concinetous mind.
The video for the song is especially excellent.
She took the money usually dedicated to making a video and using "Frontpage" demonstrated what she and her studio did with the money in thrid world countries.
They fed people, schooled people, vaccinated people, sheltered people and simply helped a bunch of people.
The thought of somebody caring enough to sacrifice gain for giving brings a tear to my eye.
Give the song a listen and know that there's an artist out there who cares about more than themselves.
Be Worried, Be Very Worried
That was the coverpage from Time magazine back in April.
I intend to make a shirt out of the page which shows a polar bear stranded on an ice drift looking for another one to swim to (the sad thing is I know that she will have a hard time finding one because there are few around).
Dozens of polar bears are drowning because the ice is melting so rapidly.
Here in Canada the government is proud of Canadian diamonds with polar bears inscribed on them.
Too bad the real bears are dying and we're the cause.
Final Thought
Sorry for the rant, but, then again, not sorry.
We have to say it.
We have to say that things aren't right.
We have to say that petroleum has to stay with the dinosaurs.
We have to say that the word 'garbage' needs to be removed from human vocabulary.
We have to say it's too blasted hot and that cloudy, rainy days are blessings which keep our planet alive.
We have to say it's time to change the way we interact with our planet : now.
"When Given A Choice Between Two Paths, Take The Third Path." (Talaxian Saying)
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Without Water There Is No Life
I shed a tear or two.
Doing what?
Watching the video for "The World Is On Fire".
You can see it too : http://www.worldonfire.ca/
Caring
I hope the day comes sooner than later that I free myself from my own hurts and replace them with caring.
"When Given A Choice Between Two Paths, Take The Third Path." (Talaxian Saying)
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We urgently need to limit carbondioxide and carbonmonoxide pollution in the atmosphere. We need to lobby internationally that all rich countries should lead by example.
Matthews Bantsijang
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Desperate polar bears, take heart! More ice is on the way, even if we don't do anything ecologically correctly in the next few decades, according to National Review, June 5, 2006, pp. 35ff.
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global warming is both our fault and natures fault. We humans have polluted the earth so badely that we have created a "greenhouse effect. the sun's rays go through the atmosphere then cant get out due to the pollution in the air. but another factor is in place: the sun is getting hotter. lets but the suns life on a clock. the sun is born at dawn. right now we r at 10:36. humans have been around for only about 1 second. at 11:31 the sun will be too hot for life to exist. so yes global warming is happening.
NEVER! underestimate youth
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Sorry
I apologize for the long absence.
Thankfully, the show has remained excellent in my absence.
Oh yes.
I voted on Podcast Alley!
God save the Naked Scientists!
30 degree weekend
I apologize for the subsequent gloomy reflections, but, perhaps I and whomever reads this can decide to look at the following statements as positive, in that they display awareness and contemplation of something that is important.
Perhaps, these statements even display, the beginnings of initiative to "do" something about this.
Here on Vancouver Island, British Columbia Canada, we had a near record high weekend of temperature.
The weather is typically in the low to mid 20's.
The temperature was in the low to high 30's.
The radio commentators blithely commented on how "isn't the weather great!"
Well, the poor fellows and fillies are paid to perpetuate obliviousness.
Saying something like,
"It's hotter than it should be. Consider switching to a low emissions vehicle and recycle all you can."
Would cause people to think about something that is uncomfortable.
Most poor people are stressed out and uncomfortable enough as it is.
...i guess it is unjust for me to be judgemental.
...i'm no hero either.
but.
i do care.
and i do want to hear radio commentators say,
"Hey! You know what kits and kats? It's really too darn hot."
An Inconvenient Truth
I saw it and I am going to try to do what Al Gore wanted.
Here's one of the things he asked me, and, everyone who watched the film to do:
"Hey there fellow human being. I would like to encourage you to watch the movie 'An Inconvenient Truth'. You hear all about Global Warming. Who do you trust? I don't know. But. I do trust Al Gore. Why? A feeling. My feelings. I trust them. Watch the movie. And when you consider your position, I say : trust your feelings."
There.
Now I have to:
1. Write my parliament.
2. Buy environmentally friendly lightbulbs (check)
3. Buy a low emissions vehicle (looking at a small Toyota pickup)
4. Do an energy efficiency assessment of the house.
I still have a few things to do.
Why do I want to?
Because watching the movie opened my eyes.
and.
i felt something.
what Al Gore said,
how he said it,
the look on his face as he said it,
felt right.
he cares.
i care.
i'll do what he asked.
Proposal for a Commercial
There's a cute commercial by Coca-Cola.
The Polar Bears.
Baby bear finds some penguins.
He's curious.
He goes among them.
Papa and Mama follow baby.
They're nervous.
They're surrounded by strange penguins.
Will they hurt baby?
No!
One of the penguins gives baby a bottle of Coke.
Baby happily drinks down the cool, refreshing beverage.
Mama and Papa look on happily.
[musically] Always Coca Cola.
Watching "An Inconvenient Truth" I learned that the Polar Bears are dying out there up North.
The ice is there home.
We're taking that away.
No home.
No living.
I propose a new commercial.
I propose it to anyone who can make it.
I'll make it myself someday, if it doesn't get made.
It's still nightime.
Baby bear is happily drinking a beverage from a bottle (assumably Coke, but not coke because they'd sue) along with all his penguin friends.
Papa and Mama come over to happily look on.
The sun starts to come up.
Everyone looks out to happily greet the new day.
The suns rays gently stretch out along the icy sheet.
The rays reach the soda bottles held in polar bear paws and penguin webbed wings.
The bottles sparkle and shine and refract the rays towards the ice.
and everything goes to hell.
Rays lance out from all the soda bottles and cut into the ice.
The terrified baby bear and the penguins toss the bottles onto the ice sheet.
The bottles land on the ice but continue to collect the suns unforgiving energy and carve the ice mercilessly.
The bear family and the penguins watch in horror as geysers of water shoot out into the air and the ice sheet splits apart into countless small floes.
[cut scene]
The bear family is swimming.
They swim up to an ice floe.
Papa and Mama try to push baby on.
The floe breaks into two pieces.
They try to push baby onto one that is just big enough for baby.
It breaks.
The exhausted bears resume their desperate swimming but as the camera pans out...there is nothing but water...everywhere.
Apologies
I'm sorry.
Writing this brought tears to my eyes.
It's kind of nice though.
It's so rare for me to feel much.
Powerful things.
Hurrican Katrina.
Iraq.
These experiences have catalysed the American people to look at their leadership, themselves, and question their direction.
really question their direction.
Painful experiences.
Lots of people are dead.
They won't see if their deaths have taught the survivors anything.
Hopefully the survivors will remember for them.
Polar bears are dying out there.
It's global warming.
It's our doing.
It's our responsibility.
A powerful commercial can be another "thing" to catalyse us to question, really question, our direction.
oh yeah.
i don't drink coke (or any other soda). period.
"When Given A Choice Between Two Paths, Take The Third Path." (Talaxian Saying)
Please see Al Gore's Movie "An Inconvenient Truth". The earth is our home, our responsibility.
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While you are suffering record temperatures in British Columbia, as we are here in British England, we have reports from Texas of abnormally low temperatures for the season, as England is warmer than the Med. Is it thus really appropriate to talk of global warming, or just a shift of hotspots from one point in the globe to another?
Beyond that issue of extrapolating too much from too small a data base, one also has to ask about the assumption of causal link. We know that weather has been getting warmer since the 1660's, and that this has been due to changes in solar output, and all the emission reduction in the world wont change that.
As for human pollution – much of it may actually have helped cool the world, and the reduction in particulate matter caused by cleaner factories may actually have increased the amount of solar radiation reaching the soil.
All of the attempt I have heard about to model the climate based upon the assumption that greenhouse gasses play a significant part in global warming have singularly failed to accurately predict anything. Ofcourse, it may be that just one little tweak in the model may get everything exactly right, but it is just as likely that the underlying assumptions are completely wrong.
George
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George this is true! It has been cooler for us the last 2 days...90's...and cool breeze.
"Lo" Loretta
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Alright guys, im in need of some criticism.
Supposedly heat cannot be destroyed, correct?
It only dissipates from one cooler object or body of matter to another, so suppose that our global warming isnt attributed to the ozone effect but the fact that in the past century, human beings have created much more heat energy through forms such as industrialization and the growth of fuel burning products. Also take into account the increasing population which is constantly growing with each year. The chemical reactions that take place within our body create heat too, so could the increased population plus recent industrialization (recent in relation to the age of the earth) have anything to do with the increased global temperatures we are experiencing? I'm probably very misinformed and sounding like an idiot, but it was a thought that crossed my mind while sitting in physics class.
Anywayz, criticize away!
-Timmy-
"Science Rules"
Bill Nye The
Science Guy
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quote:
Originally posted by Acoustic Samurai
so suppose that our global warming isnt attributed to the ozone effect but the fact that in the past century, human beings have created much more heat energy through forms such as industrialization and the growth of fuel burning products.
Minor correction – much of the argument for greenhouse heating has little to do with the ozone issue – I think you are confusing two different matters.
The Earth can cool itself down if it radiates heat out into space. This is one of the arguments the proponents of the greenhouse gas theory claim, that an increase in CO2 that still is measured in a few hundred parts per million is sufficient to significantly handicap the Earth's ability to radiate heat out into space.
On the broader issue, it seems a more plausible argument to me than the greenhouse gas argument – the question is whether we actually are producing enough energy to have much impact.
I did put forward a question to the forum that might give some indication whether we do produce enough energy to significantly increment the temperature of the planet - http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=4841
If the energy we are producing were as much as 1% of the energy that the Earth receives from the Sun from fossil fuels, then it would mean that we may be raising the Earth's temperature by about 2.8 degrees celcius.
The question is whether human energy production is in that order of magnitude.
Ofcourse, if we do use that much energy, then it follows that there is absolutely no way we can substitute 'renewable' energy sources for our fossil fuel sources, since I think it unlikely that we could ever have access to even 1% of the solar energy reaching this planet, and if we did, we would have to deprive the rest of the ecosystem of the use of that energy.
quote:
Also take into account the increasing population which is constantly growing with each year. The chemical reactions that take place within our body create heat too, so could the increased population plus recent industrialization (recent in relation to the age of the earth) have anything to do with the increased global temperatures we are experiencing?
It is unlikely that out population increase will have much impact on global energy production since for the most part we are removing other animal species from the planet at about the same rate, so I imagine the two processes would about cancel each other out.
quote:
I'm probably very misinformed and sounding like an idiot, but it was a thought that crossed my mind while sitting in physics class.
No more than the rest of us – if you don't ask, you won't find an answer.
George
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http://www.climateprediction.net/board/viewtopic.php?t=2723
covers the same ground. Not sure if the calculations are accurate but the conclusion was that CO2 is massively more important than that of all mankinds energy creation.
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quote:
Originally posted by crandles
http://www.climateprediction.net/board/viewtopic.php?t=2723
covers the same ground. Not sure if the calculations are accurate but the conclusion was that CO2 is massively more important than that of all mankinds energy creation.
I have no way of knowing if the figures they quote are accurate, but it does indicate that our own energy production is still only a fraction of what the Sun is presently giving us, and thus of little concern.
The figures they have used are (as I said, I have no idea if they are correct):
quote:
Energy recieved from sun:
radius of earth = 10,000 km
energy in incident radiation = 2.4 kw/m2
proportion of incident radiation absorbed = 0.2
Total rate of energy absorption = 1.5 x 10^14 kw
Energy consumed by people:
No of people = 6bn
Energy consumption per head = 30 kwh/day (this is my wildest guess)
proportion released as heat = 100%
Total rate of heat production = 7.5 x 10^9 kw
Ratio of man made heat to solar heat = 5 x 10^-5
I do not see any figures there about what the actual level of reduced radiation into space would be if there was a doubling or tripling of the current 300ppm or so proportion of the atmosphere that is CO2 (in geological time, there have been 5 fold increases over this, and it has not caused a runaway greenhouse effect – and although the increase in CO2 has historically been associated with rise in global temperature, it has not been demonstrated that it causes, rather than is caused by, rises in global temperature -and we know that factor other than CO2 are at least partly responsible for changes in temperature, and may even be wholly responsible for it).
George
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You are right about the comparisons being between mankinds energy production versus solar energy so I should not have suggested the CO2 being massively more important based on that thread.
I agree that the historical correlation alone does not provide very good evidence of causality. There are even lags in a few places suggesting the initial rise is not caused by CO2.
However, the totality of the evidence is much greater than the historical correlation. The science of how CO2 acts as a greenhouse gas is well understood. Without feedbacks, we are sure there would be a positive feedback of approx 1C for a doubling of CO2. The feedbacks are less certain but the main ones we know of increased water vapour and ice albedo are positive. There are several independant lines of research that suggest the climate sensitivity is about 3C
http://julesandjames.blogspot.com/2006/03/climate-sensitivity-is-3c.html
http://julesandjames.blogspot.com/2006/03/new-improved-estimate-of-climate.html#comments
Dr Annan is clearly bored with climate sensitivity now:
http://julesandjames.blogspot.com/2006/07/mission-impossible.html
If you want to suggest there are negative feedbacks such that climate sensitivity might even be negative then you are going to have to come up with some important feedbacks that are currently unknown and provide reasons why all those different estimates are wrong. If there was no positive climate sensitivity, you would also have to explain the unpresidented rates of warming at coincidentally just the time we would expect rises if there was a positice climate sensitivity.
You are right about there being factors other than CO2 but we know more than nothing about many of them else we could not produce figure a of 12.7:
http://www.grida.no/climate/ipcc_tar/wg1/450.htm
A positive feedback does not necessarily lead to a "runaway greenhouse effect" so because we haven't had one at 5 fold the CO2 level this may provide confort we won't get one if the same conditions arose again. However, it doesn't mean that there are not positive feedbacks.
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See also:
What does the lag of CO2 behind temperature in ice cores tell us about global warming?
http://www.realclimate.org/index.php?p=13
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quote:
Originally posted by crandles
See also:
What does the lag of CO2 behind temperature in ice cores tell us about global warming?
http://www.realclimate.org/index.php?p=13
This seems like a very selective interpretation of the data. Ofcourse, being selective does not make it provably wrong, only that it makes it suspect.
There is a clear acceptance that the first 800 years of global warming (in the historic records of past warm periods) was not caused by CO2. It then suggests we can ignore this 800 years when we look at the subsequent 4,200 years. While it is true that we cannot prove that the subsequent 4,200 years have the same cause of warming as the preceding 800 years; but would not Occam's razor suggest that we should first look for one mechanism, rather than postulate two separate mechanisms. Ofcourse, Occam's razor is not always right, but why assume it to be wrong before having shown it to be wrong?
Furthermore, since it is clear that historic CO2 levels have consistently risen after the initial rise in temperature, we may reasonably deduce that there are non-anthropogenic mechanisms within the biosphere that actually cause a rise in CO2 as a consequence of rising temperature. To what extent can we even be sure that present rises in CO2 levels are actually caused by human activity, and to what extent are they themselves part of the mechanisms that have in the past been a response to increasing global temperatures (the fact that humans produce CO2 does not of itself prove that humans control the balance between CO2 and O2).
George
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quote:
Originally posted by crandles
However, the totality of the evidence is much greater than the historical correlation. The science of how CO2 acts as a greenhouse gas is well understood.
There should be one very important piece of evidence that should be available to us to help indicate the magnitude of the greenhouse effect. I have yet to find anywhere on the Internet any publication of this evidence.
If the current presumed rise in CO2 levels on Earth are reducing heat radiation into space, then we should actually see a significant reduction of emitted energy in the infra-red pictures of the Earth taken by weather satellites over the last few decades. Is such a reduction in infra-red emission actually observed in satellite photos?
quote:
Without feedbacks, we are sure there would be a positive feedback of approx 1C for a doubling of CO2. The feedbacks are less certain but the main ones we know of increased water vapour and ice albedo are positive. There are several independant lines of research that suggest the climate sensitivity is about 3C
If you want to suggest there are negative feedbacks such that climate sensitivity might even be negative then you are going to have to come up with some important feedbacks that are currently unknown and provide reasons why all those different estimates are wrong. If there was no positive climate sensitivity, you would also have to explain the unpresidented rates of warming at coincidentally just the time we would expect rises if there was a positice climate sensitivity.
The climate is dynamic, but with multiple stable (transiently) states. In order to be able to achieve such short term stability, there must be negative feedback loops. In order to switch states, there must also be positive feedback loops. I do not think one can discuss whether there are positive or negative feedback loops, but must inevitably accept that there are both, most of which we have not the slightest understanding of.
George
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http://www.climateprediction.net/board/viewtopic.php?t=2723
covers the same ground. Not sure if the calculations are accurate but the conclusion was that CO2 is massively more important than that of all mankinds energy creation.
-
quote:
Originally posted by crandles
http://www.climateprediction.net/board/viewtopic.php?t=2723
covers the same ground. Not sure if the calculations are accurate but the conclusion was that CO2 is massively more important than that of all mankinds energy creation.
I have no way of knowing if the figures they quote are accurate, but it does indicate that our own energy production is still only a fraction of what the Sun is presently giving us, and thus of little concern.
The figures they have used are (as I said, I have no idea if they are correct):
quote:
Energy recieved from sun:
radius of earth = 10,000 km
energy in incident radiation = 2.4 kw/m2
proportion of incident radiation absorbed = 0.2
Total rate of energy absorption = 1.5 x 10^14 kw
Energy consumed by people:
No of people = 6bn
Energy consumption per head = 30 kwh/day (this is my wildest guess)
proportion released as heat = 100%
Total rate of heat production = 7.5 x 10^9 kw
Ratio of man made heat to solar heat = 5 x 10^-5
I do not see any figures there about what the actual level of reduced radiation into space would be if there was a doubling or tripling of the current 300ppm or so proportion of the atmosphere that is CO2 (in geological time, there have been 5 fold increases over this, and it has not caused a runaway greenhouse effect – and although the increase in CO2 has historically been associated with rise in global temperature, it has not been demonstrated that it causes, rather than is caused by, rises in global temperature -and we know that factor other than CO2 are at least partly responsible for changes in temperature, and may even be wholly responsible for it).
George
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You are right about the comparisons being between mankinds energy production versus solar energy so I should not have suggested the CO2 being massively more important based on that thread.
I agree that the historical correlation alone does not provide very good evidence of causality. There are even lags in a few places suggesting the initial rise is not caused by CO2.
However, the totality of the evidence is much greater than the historical correlation. The science of how CO2 acts as a greenhouse gas is well understood. Without feedbacks, we are sure there would be a positive feedback of approx 1C for a doubling of CO2. The feedbacks are less certain but the main ones we know of increased water vapour and ice albedo are positive. There are several independant lines of research that suggest the climate sensitivity is about 3C
http://julesandjames.blogspot.com/2006/03/climate-sensitivity-is-3c.html
http://julesandjames.blogspot.com/2006/03/new-improved-estimate-of-climate.html#comments
Dr Annan is clearly bored with climate sensitivity now:
http://julesandjames.blogspot.com/2006/07/mission-impossible.html
If you want to suggest there are negative feedbacks such that climate sensitivity might even be negative then you are going to have to come up with some important feedbacks that are currently unknown and provide reasons why all those different estimates are wrong. If there was no positive climate sensitivity, you would also have to explain the unpresidented rates of warming at coincidentally just the time we would expect rises if there was a positice climate sensitivity.
You are right about there being factors other than CO2 but we know more than nothing about many of them else we could not produce figure a of 12.7:
http://www.grida.no/climate/ipcc_tar/wg1/450.htm
A positive feedback does not necessarily lead to a "runaway greenhouse effect" so because we haven't had one at 5 fold the CO2 level this may provide confort we won't get one if the same conditions arose again. However, it doesn't mean that there are not positive feedbacks.
-
See also:
What does the lag of CO2 behind temperature in ice cores tell us about global warming?
http://www.realclimate.org/index.php?p=13
-
quote:
Originally posted by crandles
See also:
What does the lag of CO2 behind temperature in ice cores tell us about global warming?
http://www.realclimate.org/index.php?p=13
This seems like a very selective interpretation of the data. Ofcourse, being selective does not make it provably wrong, only that it makes it suspect.
There is a clear acceptance that the first 800 years of global warming (in the historic records of past warm periods) was not caused by CO2. It then suggests we can ignore this 800 years when we look at the subsequent 4,200 years. While it is true that we cannot prove that the subsequent 4,200 years have the same cause of warming as the preceding 800 years; but would not Occam's razor suggest that we should first look for one mechanism, rather than postulate two separate mechanisms. Ofcourse, Occam's razor is not always right, but why assume it to be wrong before having shown it to be wrong?
Furthermore, since it is clear that historic CO2 levels have consistently risen after the initial rise in temperature, we may reasonably deduce that there are non-anthropogenic mechanisms within the biosphere that actually cause a rise in CO2 as a consequence of rising temperature. To what extent can we even be sure that present rises in CO2 levels are actually caused by human activity, and to what extent are they themselves part of the mechanisms that have in the past been a response to increasing global temperatures (the fact that humans produce CO2 does not of itself prove that humans control the balance between CO2 and O2).
George
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quote:
Originally posted by crandles
However, the totality of the evidence is much greater than the historical correlation. The science of how CO2 acts as a greenhouse gas is well understood.
There should be one very important piece of evidence that should be available to us to help indicate the magnitude of the greenhouse effect. I have yet to find anywhere on the Internet any publication of this evidence.
If the current presumed rise in CO2 levels on Earth are reducing heat radiation into space, then we should actually see a significant reduction of emitted energy in the infra-red pictures of the Earth taken by weather satellites over the last few decades. Is such a reduction in infra-red emission actually observed in satellite photos?
quote:
Without feedbacks, we are sure there would be a positive feedback of approx 1C for a doubling of CO2. The feedbacks are less certain but the main ones we know of increased water vapour and ice albedo are positive. There are several independant lines of research that suggest the climate sensitivity is about 3C
If you want to suggest there are negative feedbacks such that climate sensitivity might even be negative then you are going to have to come up with some important feedbacks that are currently unknown and provide reasons why all those different estimates are wrong. If there was no positive climate sensitivity, you would also have to explain the unpresidented rates of warming at coincidentally just the time we would expect rises if there was a positice climate sensitivity.
The climate is dynamic, but with multiple stable (transiently) states. In order to be able to achieve such short term stability, there must be negative feedback loops. In order to switch states, there must also be positive feedback loops. I do not think one can discuss whether there are positive or negative feedback loops, but must inevitably accept that there are both, most of which we have not the slightest understanding of.
George
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quote:
The climate is dynamic, but with multiple stable (transiently) states. In order to be able to achieve such short term stability, there must be negative feedback loops. In order to switch states, there must also be positive feedback loops. I do not think one can discuss whether there are positive or negative feedback loops, but must inevitably accept that there are both, most of which we have not the slightest understanding of.
What makes you so sure of this? Why cannot the appearance of multiple stable states be a result of the forcings applied eg Milankovitch cycles (http://en.wikipedia.org/wiki/Milankovitch_cycle). To first order, the most important consideration is that the hotter the earth the more heat it ratiates. This creates the stability in the same manner as the leaky bucket analogy. A steady state can be reached. Reduce the size of the hole and the water level starts to rise but it doesn't necessarily overflow the bucket a new equilibrium level is likely to be reached because the flow out of the hole depends on the height of water.
Since there appear to be net positive feedbacks at more than one point in time (eg current, LGM, and other times from which estimates of climate sensititivity have been made), it is possible that at another point in time the net feedbacks could be different but that doesn't mean they are likely to become negative and I suggest that the experts know enough to say they are very unlikely to become negative soon.
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quote:
This seems like a very selective interpretation of the data. Ofcourse, being selective does not make it provably wrong, only that it makes it suspect.
There is a clear acceptance that the first 800 years of global warming (in the historic records of past warm periods) was not caused by CO2. It then suggests we can ignore this 800 years when we look at the subsequent 4,200 years. While it is true that we cannot prove that the subsequent 4,200 years have the same cause of warming as the preceding 800 years; but would not Occam's razor suggest that we should first look for one mechanism, rather than postulate two separate mechanisms. Ofcourse, Occam's razor is not always right, but why assume it to be wrong before having shown it to be wrong?
George
This is actually funny. [:o)] Who is being selective? Is it the climatologists at realclimate for ignoring the other cause?
or could, just perhaps, it be the case that they are considering both causes of warming (one known to have a positive contribution and the other which is unknown whether it continues or not) and it is you being selective in wanting to consider only one cause of warming and deliberately ignoring the CO2 when that is the cause we know to have a greenhouse effect which will have a positive effect on temperature.
I don't think occam razor suggests ignoring a known cause in favour of an unknown one.
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quote:
Originally posted by another_someone
Furthermore, since it is clear that historic CO2 levels have consistently risen after the initial rise in temperature, we may reasonably deduce that there are non-anthropogenic mechanisms within the biosphere that actually cause a rise in CO2 as a consequence of rising temperature. To what extent can we even be sure that present rises in CO2 levels are actually caused by human activity, and to what extent are they themselves part of the mechanisms that have in the past been a response to increasing global temperatures (the fact that humans produce CO2 does not of itself prove that humans control the balance between CO2 and O2).
George
We are pretty sure. We are putting 7 gigatones of carbon into the atmosphere each year through burning fossil fuels and when we measure the atmosphere 4 gigatones per year are accumulating in the atmosphere. The ocean is disolving most of the balance causing it to become more acidic. Prior to the industrial revolution CO2 had been pretty much stable in the atmosphere. So to raise uncertainty about us being the cause you are going to have to find some pretty big natural sources to have started at just the right time as well as methods for our CO2 to be dealt with naturally.
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quote:
Originally posted by crandles
What makes you so sure of this? Why cannot the appearance of multiple stable states be a result of the forcings applied eg Milankovitch cycles (http://en.wikipedia.org/wiki/Milankovitch_cycle). To first order, the most important consideration is that the hotter the earth the more heat it ratiates. This creates the stability in the same manner as the leaky bucket analogy. A steady state can be reached. Reduce the size of the hole and the water level starts to rise but it doesn't necessarily overflow the bucket a new equilibrium level is likely to be reached because the flow out of the hole depends on the height of water.
Since there appear to be net positive feedbacks at more than one point in time (eg current, LGM, and other times from which estimates of climate sensititivity have been made), it is possible that at another point in time the net feedbacks could be different but that doesn't mean they are likely to become negative and I suggest that the experts know enough to say they are very unlikely to become negative soon.
A system that has pure positive feedback, and no negative feedback component, will always be in a runaway condition – this is not what the Earth has ever done historically.
Even with regard to Venus, which is often cited as a runaway condition that the Earth could fall in to – it is not at all in a runaway condition – Venus is relatively stable (possibly even more stable than the Earth), but is merely stable at a higher temperature.
Thus, to avoid runaway, you must either have absolutely no feedback, or a substantial component of negative feedback. Since we know that we do not have a condition on Earth where there is no feedback, thus we may reasonably surmise that there are substantial negative feedback processes in place.
George
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quote:
Originally posted by crandles
This is actually funny. [:o)] Who is being selective? Is it the climatologists at realclimate for ignoring the other cause?
or could, just perhaps, it be the case that they are considering both causes of warming (one known to have a positive contribution and the other which is unknown whether it continues or not) and it is you being selective in wanting to consider only one cause of warming and deliberately ignoring the CO2 when that is the cause we know to have a greenhouse effect which will have a positive effect on temperature.
I don't think occam razor suggests ignoring a known cause in favour of an unknown one.
We are not here looking at a known cause versus an unknown cause.
What we are talking about is an observed, but not understood, cause; and a hypothesised but not definitely observed cause.
What I am saying is when one compares hypothesis to observation, observation should always take precident.
We know there is a cause of global warming that does not include CO2, although we have no hypothesis that yet explains what it is. We know that rises in CO2 seem to follow (not lead) these rises in temperature, and thus may infer (although cannot with certainty know) that CO2 rises are caused by rises in temperature.
We have a hypothesis that suggests that increased levels of CO2 should cause rises in temperature – yet we have no quantitative observations of such an effect that could unambiguously show this to happen.
A few things we do know:
- Temperature rises can occur even in the absence of rising CO2.
- Temperature falls can happen even after CO2 levels have risen.
We have a hypothesis that suggests that temperatures should rise after an increase in CO2 levels, and that temperatures will continue to remain high as long as CO2 levels remain high. We know that this hypothesis conflicts with observation. We can certainly suggest that there are unknown factors that conflict with the hypothetical case, but since we have not explained in any way what these unknown factors are, thus we have no way of knowing whether the hypothetical situation present any significant input into the real and observed results.
I accept that the hypothetical feedback cycle probably has some impact, but what I cannot accept is that it has any impact of significant quantitative levels that they may be observed against all the other (mostly unknown, although clearly present) factors that do affect global temperatures.
George
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quote:
Originally posted by another_someone
A system that has pure positive feedback, and no negative feedback component, will always be in a runaway condition – this is not what the Earth has ever done historically.
Sorry but that is rubbish. Feedback can be positive but less than a factor of 1 and then you won't get a runaway condition.
Take something really simple like
xi=x(i-1)+forcing+feedback factor * ( x(i-1) - x(i-2) )
try it out with a feedback factor of greater than 1 and you do get a runaway condition. Try it with a feedback factor of between 0 and 1 and you do not get a runaway effect. The eventual change is greater than the forcing so the feedback is positive but there is no runaway effect.
The above alone defeats your "will always be"
With temperature it is much harder to get a runaway effect because of the first order effect that a hotter planet emits more radiation.
Sorry - I think I accidentally edited your post - hopefully back to where it should be.
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quote:
We have a hypothesis that suggests that temperatures should rise after an increase in CO2 levels, and that temperatures will continue to remain high as long as CO2 levels remain high. We know that this hypothesis conflicts with observation.
Do you want to try again on that one?
800 years is less than 20% of the 5000 year period. Given that there are lots of these periods and some show those 800 year periods and that the hypothesis is that CO2 (not alone but among other things affects temperature) then that is good observational evidence that CO2 does have the effect expected and that other causes do not dominate over the effect of CO2.
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quote:
Originally posted by another_someone
Sorry but that is rubbish. Feedback can be positive but less than a factor of 1 and then you won't get a runaway condition.
Take something really simple like
xi=x(i-1)+forcing+feedback factor * ( x(i-1) - x(i-2) )
try it out with a feedback factor of greater than 1 and you do get a runaway condition. Try it with a feedback factor of between 0 and 1 and you do not get a runaway effect. The eventual change is greater than the forcing so the feedback is positive but there is no runaway effect.
The above alone defeats your "will always be"
Sorry, but how is the above a pure positive feedback mechanism – you have a term -x(i-2) – by my reckoning that amounts to a negative term, and thus a negative feedback component.
quote:
With temperature it is much harder to get a runaway effect because of the first order effect that a hotter planet emits more radiation.
But that too is a negative feedback, since it is a factor that increases the cooling as an increase in temperature occurs.
Ofcourse, as long as the effect is linear, then the effect will only reduce the rate of runaway, but not be sufficient to stop it. If you can demonstrate that proportion of temperature radiated increases with increasing temperature, then you would maybe be able to show it was sufficient to stop runaway; but at present, the indications are actually contrary, that as temperature increases, so the amount of ice on our planet reduces, and so the albedo of our planet reduces, and so the negative feedback becomes less effective (i.e. we have a positive feedback cycle that dominates over the negative feedback cycles). Ofcourse, there may be other planets, with different surface chemistries, that might have a different relationship between albedo and surface temperature.
George
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quote:
Sorry, but how is the above a pure positive feedback mechanism – you have a term -x(i-2) – by my reckoning that amounts to a negative term, and thus a negative feedback component.
Sorry not sure how to do subscripts on this forum yet. The i, i-1 and i-2 terms are all supposed to indicate time periods.
So start at a temperature of 10C. Apply a forcing that causes a 1C rise (This could be doubling of CO2 or something else. The temp initially goes to 11C then the feedback starts kicking in. If the feedback factor is 0.5 the temp would go to 11.5 then 11.75 then 11.875 and so on up to 11.999999. That is clearly a positive feedback that does not not lead to a runaway effect.
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Ofcourse, as long as the effect is linear, then the effect will only reduce the rate of runaway, but not be sufficient to stop it. If you can demonstrate that proportion of temperature radiated increases with increasing temperature, then you would maybe be able to show it was sufficient to stop runaway; but at present, the indications are actually contrary, that as temperature increases, so the amount of ice on our planet reduces, and so the albedo of our planet reduces, and so the negative feedback becomes less effective (i.e. we have a positive feedback cycle that dominates over the negative feedback cycles). Ofcourse, there may be other planets, with different surface chemistries, that might have a different relationship between albedo and surface temperature.
No it is basic physics that a hotter body radiates more heat.
(Therefore the effects are much less than linear. This is why climate sensitivity is defined in terms of the effect of doubling CO2 you have to increase CO2 much more than linearly to get a constant response.)
The ice albedo effect is a positive feedback not a negative one. But is is not strong enough to overcome the first order effect that hotter bodies radiate more heat.
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quote:
Originally posted by another_someone
quote:
With temperature it is much harder to get a runaway effect because of the first order effect that a hotter planet emits more radiation.
But that too is a negative feedback, since it is a factor that increases the cooling as an increase in temperature occurs.
No that is part of the system not a feedback.
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quote:
Originally posted by crandles
Do you want to try again on that one?
800 years is less than 20% of the 5000 year period. Given that there are lots of these periods and some show those 800 year periods and that the hypothesis is that CO2 (not alone but among other things affects temperature) then that is good observational evidence that CO2 does have the effect expected and that other causes do not dominate over the effect of CO2.
Sorry, but all that the coincidence between rises in CO2 and increased temperature shows is correlation, not causality. The fact that increased temperature precedes increases in CO2 is strongly indicative (but does not prove) that CO2 responds to temperature. Anything else is pure hypothesis.
Ofcourse, so long as there is observable coincidence, it is valid to ask whether there is a two way causality; but there is no necessity to assume this simply to explain the observed evidence.
George
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quote:
Originally posted by crandles
Sorry not sure how to do subscripts on this forum yet. The i, i-1 and i-2 terms are all supposed to indicate time periods.
Neither do I, but I did understand what you were saying.
quote:
So start at a temperature of 10C. Apply a forcing that causes a 1C rise (This could be doubling of CO2 or something else. The temp initially goes to 11C then the feedback starts kicking in. If the feedback factor is 0.5 the temp would go to 11.5 then 11.75 then 11.875 and so on up to 11.999999. That is clearly a positive feedback that does not not lead to a runaway effect.
The system as you described it was :
xi=x(i-1)+forcing+feedback factor * ( x(i-1) - x(i-2) )
this can be expanded to:
xi=x(i-1)+forcing + feedback factor * x(i – 1) - feedback factor * x(i – 2)
In other words, there is a component of the output (from two time slices earlier) that is subtracted from the input – this makes it negative feedback. There is also a component (from the immediately preceding time slice) where the output is added to the input, and this is a positive feedback. So your system contains both positive and negative feedback components.
George
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quote:
Originally posted by crandles
quote:
Originally posted by another_someone
quote:
With temperature it is much harder to get a runaway effect because of the first order effect that a hotter planet emits more radiation.
But that too is a negative feedback, since it is a factor that increases the cooling as an increase in temperature occurs.
No that is part of the system not a feedback.
I will probably grant you this (at least insofar as the effect is linear), because it is an effect that is purely dependent upon the inputs to the system, and not dependent upon any function or output of the system itself.
Nonetheless, any non-linearity (such as caused by changes in albedo, or changes in heat retention, must be regarded as feedback effects, since they are caused by changes in state of the system that is itself caused by previous inputs into the system).
George
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The initial forcing pushes it up from 10 to 11. The new equilibrium level is 12. Therefore the effect of a feedback factor of 0.5 is to increase the movement of the system in the same direction therefore this feedback is positive.
To quote http://en.wikipedia.org/wiki/Positive_feedback
quote:
When a change of variable occurs in a system, the system responds. In the case of positive feedback the response of the system is to change that variable even more in the same direction.
How is what I have shown not a positive feedback?
Artificially spliting my feedback funtion into two simply is not appropriate.
(edit spelling)
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quote:
Originally posted by crandles
Artificially spliting my feedback funtion into two simply is not appropriate.
It is not an artificial splitting of your feedback function.
http://en.wikipedia.org/wiki/Feedback
quote:
In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. Often this is done intentionally, in order to control the dynamic behavior of the system. Feedback is observed or used in various areas dealing with complex systems, such as engineering, architecture, economics, and biology. Continuous feedback in a system is a feedback loop.
x(i-1) and x(i-2) are two different feedback paths (they must have different paths, because they have different delays), so they must be regarded as separate feedbacks loops. You bundling them into one feedback path is artificial, because the fact that they have different time delays means they cannot have the same path.
George
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( x(i-1) - x(i-2) ) could have been written as delta x (ie the change in the x variable) lagged by a timestep.
But suppose I describe another system which initially is in equilibrium at 10 we apply a forcing which moves the system to 11 then a feedback kicks in equal to 3 times the forcing (lagged by 1 timestep so the system moves to 14 and it then stays in equilibrium at 14.
Surely there is no negative feedback in that system and it does not go into a runaway effect.
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quote:
Originally posted by crandles
But suppose I describe another system which initially is in equilibrium at 10 we apply a forcing which moves the system to 11 then a feedback kicks in equal to 3 times the forcing (lagged by 1 timestep so the system moves to 14 and it then stays in equilibrium at 14.
Surely there is no negative feedback in that system and it does not go into a runaway effect.
Sorry, I cannot see any description of what might be regarded as a complete system.
A system needs inputs and outputs (the closest to an input would be what you call a 'forcing'), and a complex system will normally have some feedback that moves some of the output back into the input.
You have said the system is initially at equilibrium at 10 – you have not told me how this equilibrium is maintained? One assumes that in order to maintain an equilibrium, there must be negative feedback (one cannot otherwise maintain sustained equilibrium over a range of inputs, since the only way of offsetting changes in input is to feedback some of the output to cancel the input). What is the nature of this feedback, and how does it alter with further changes in input?
You suggest that with a further increase in input (of some unknown amount), the negative feedback is sufficiently overwhelmed to allow the output to drift to 11 – but then there is a step change in the feedback that reduces the negative feedback (or possibly changes it to a net positive feedback) until the output climbs to 14, and then switches back to another negative feedback that holds it steady there.
What you have described is a system with multiple stable regions (an astable system), but you have in no way described mathematically (let alone physically) what the feedback mechanisms are that create this astable system.
George
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I cannot believe you are not accepting the obvious that a positive feedback does not always cause a runaway effect.
Suppose:
A barrel contains 120 litres of water. The inflow appears fixed at 12 litres a minute. The outflow depends on the height of the water and so is equal to 10% of the volume in the barrel per minute.
This is currently in equilibrium. We now reduce the size of the hole so the the outflow is only .075 times the volume in the barrel (units still litres per minute). Given the current knowledge of the system we would expect a new equilibium to be reached with the barrel containing 160 litres and inflow and outflow equal to 12 litres per minute.
In fact we notice the quantity in the barrel goes above 160 lites so we investigate and discover that the inflow is not fixed at 12 litres a minute but there is a system feedback such that if the outflow in one minute is greater than 9% of the volume in the barrel then the inflow is fixed at 12 litres per minute but if the outflow is less than 9% of the volume then the inflow is set at 15 litres per minute.
This system reaches an equilibrium with 200 litres in the barrel.
This is a positive feedback because the feedback moves the system more in the same direction (increasing volume in the barrel in this example).
The system reaches an equilibrium and does not suffer a runaway effect.
Hopefully that is an adequate description of a system. Now will you accept the obvious?
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quote:
Originally posted by crandles
Suppose:
A barrel contains 120 litres of water. The inflow appears fixed at 12 litres a minute. The outflow depends on the height of the water and so is equal to 10% of the volume in the barrel per minute.
This is currently in equilibrium.
We now reduce the size of the hole so the the outflow is only .075 times the volume in the barrel (units still litres per minute). Given the current knowledge of the system we would expect a new equilibium to be reached with the barrel containing 160 litres and inflow and outflow equal to 12 litres per minute.
In fact we notice the quantity in the barrel goes above 160 lites so we investigate and discover that the inflow is not fixed at 12 litres a minute but there is a system feedback such that if the outflow in one minute is greater than 9% of the volume in the barrel then the inflow is fixed at 12 litres per minute but if the outflow is less than 9% of the volume then the inflow is set at 15 litres per minute.
Sorry, this statement does not make sense.
You cannot 'fix' the input of a system – the whole point about an input is that it is not controlled by the system itself. The external inputs cannot be limited to either 12 or 15 litres/minute – they can be absolutely anything, since they cannot be controlled by the system – if they are controlled by the system, then they cease to be external inputs and must be regarded as part of the system.
Ofcourse, you can say that there is a negative feedback system that compensates for any external attempt to increase flow above either 12 or 15 litres/minute, and a positive feedback that allows a switch between the two stable states.
If I have a barrel of water, and a tap above that barrel of water – the barrel of water cannot control how much I turn on that tap. Ofcourse, it can have a negative feedback system that causes that if the outflow each minute if less than 9% of the contents, then any water in excess of 15 litres/minute that I allow to flow out of the tap would be deflected so as not to enter the barrel – but that requires a negative feedback mechanism. The barrel cannot cause me to switch off the tap, unless I become a part of the system (e.g. I look into the barrel, and make decisions according to what I see, and thus become a part of the negative feedback mechanism).
The system you describe is a bistable system, which is not at all an uncommon situation, but it requires a mix of positive and negative feedbacks to maintain it – a positive feedback to allow it to switch between stable states, and a negative feedback to maintain one or other stable state.
What you are suggesting is a system that creates a nett positive feedback over a very narrow range, and a nett negative feedback outside of that range.
George
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The above system is an analogy to the climate system. The height of water in the barrel represents temperature. The volume of water is a quantity of heat energy and flows of water are flows of heat energy.
We can change the size of the holes which is analogous to increasing CO2 in the atmosphere to reduce the rate infrared outgoing radiation below what would otherwise be expected for the temperature. This causes temperature and heat in the system to rise. Temperature increasing melts ice causing a positive albedo feedback effect where the system accepts more incoming radiation from the sun rather than it being reflected.
Thus I am not only arguing that positive feedback does not lead to a runaway effect but I am also arguing about the particular case of the climate system and the ice albedo positive feedback is not expected to cause runaway climate change.
It probably wasn't a good system to use for the purpose of showing that positive feedback does not have to lead to a runaway effect because there is negative feedback on the outward energy flow but not on the height/volume of water.
Not really sure why you cannot accept the size of the hole as an input which is under my control. The output I am interested in is the height/volume of water. Nor do I understand you calling it a bistable system as I can change the input, the size of the hole and get equilibriums at an infinite number of different volumes of water in the barrel.
A new system comprises a tower of building blocks plus my neice.
The system is currently in equilibrium at 5 blocks high. I apply a forcing of adding a block. This in the absence of feedback would be expected to move the system to a new equilibrium of 6 blocks high. However there is a feedback in this system, my neice is playing copycat and does whatever I do to the tower. Thus the system actually moves to a new equilibrium level of 7. This is therefore a positive feedback as it moves the system in the same direction. The system does not result in a runaway high tower (or no tower). Therefore not all positive feedbacks lead to a runaway effect.
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A heat wave in the UK has been happening and I think temperatures have reached 37 degrees celsius.
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quote:
Originally posted by Mjhavok
A heat wave in the UK has been happening and I think temperatures have reached 37 degrees celsius.
They did that a week or two back, but they are far more tollerable right now.
George
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I h8 it lol. Anything that makes me sweat more than normal (apart from the obvious fun thing) means I usually don't like it. I also skin in the non cancer variety.