Are we responsible for climate change?

djpbarry

I know this subject has been discussed at length on other threads, but I wanted to see peoples' responses to a poll on the subject.

I would be interested to see people support their responses with a post explaining their reasoning, particularly in the case of those who believe we are not responsible for climate change.

As a scientist myself who has studied the evidence, I find it hard to understand why so many people have difficulty accepting the consensus of the scientific community on this subject. Have the sceptics considered the evidence that has been presented, or is their opinion based purely on personal views and/or mistrust of authorities?

cavedave

As a scientist myself who has studied the evidence, I find it hard to understand why so many people have difficulty accepting the consensus of the scientific community on this subject.

I believe in manmade climate change. I use the word believe because I do not know enough climate physics to properly critique the models.
I am a scientist and have concerns about the accuracy of climate simulations. The climate is such a complicated thing that basing everything on simulations is dodgy. For example the Artic ice sheet seems to be melting decades ahead of schedule which says that our predictive models are extremely flawed.

djpbarry

cavedave wrote: »

I am a scientist and have concerns about the accuracy of climate simulations. The climate is such a complicated thing that basing everything on simulations is dodgy. For example the Artic ice sheet seems to be melting decades ahead of schedule which says that our predictive models are extremely flawed.

I understand what you're saying - the Earth's climate is an incredibly complex system. But, climate scientists have never pretended to fully understand it. In fact, the IPCC have explicitly stated that there is limited understanding of these processes:

Dynamical processes related to ice flow and not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude.

But, in my opinion, this is not the point. Arguing over how or how much the climate will change is a bit like arguing over how much damage a nuclear war will cause, rather than investing that time and energy in preventing the war in the first place.

bonkey

cavedave wrote: »

The climate is such a complicated thing that basing everything on simulations is dodgy.

Why?

Perhaps a better question I could ask is what alternatives do we have to modelling that would be preferable?

For example the Artic ice sheet seems to be melting decades ahead of schedule which says that our predictive models are extremely flawed.

This says our models are imperfect to some unquantified degree - something we already knew.

It doesn't, however, suggest that basing everything on models is inherently dodgy.


In answer to the OP, my stance would be that there is a high degree of probability that mankind is a significant driving force regarding the current global climate shifts. I base this stance on the lack of credible refutation of the science which has been done to date on the subject.

Lennoxschips

The effect of the Greenland ice sheet on sealevel rise isn't included in the models. Because nobody understands it enough.

So the current sealevel rise predictions could be considered conservative, to say the least.

cavedave

Why?

I have never written a computer program that did not have any errors. No one I know has ever written a computer program of any reasonable size that did not have any errors. Writing a computer program to simulate a process you do not really understand is unlikely to be accurate. The evidence that climate change is happening faster then predicted shows that our computer models are not accurate.

to some unquantified degree

Simulations that are vastly innaccurate says the unquantified degree is much bigger then previously thought.

*sorry image was huge. For a rough idea of how badly computer simulations underestimated arctic ice melts see here
http://climateprogress.org/wp-content/uploads/2007/09/august-ice-trend.jpg

It doesn't, however, suggest that basing everything on models is inherently dodgy.

If the theories predictions are inaccurate you have to get another theory. In Fairness not all climate change research is based on computer simulations. There are good empirical evidence on species migration, there are also (afaik) physical principles that have been tested in a laboratory setting.

Arguing over how or how much the climate will change is a bit like arguing over how much damage a nuclear war will cause, rather than investing that time and energy in preventing the war in the first place.

Say the climate changes by .0001 degrees is it worth spending 50% of gdp to prevent this? Nuclear war would pretty much kill everyone I have seen no prediction of climate change that says this will happen. You have to know the costs (or at least the extent) of climate change before any reasonable decisions about how to change our behaviour can be made.

djpbarry

cavedave wrote: »

Say the climate changes by .0001 degrees is it worth spending 50% of gdp to prevent this?

First of all, nobody is talking about spending that kind of money and besides, it is not just about spending money, it is about changing peoples' attitudes. For example, it doesn't cost anything to turn off a TV rather than leaving it on standby.

Secondly, as you have shown yourself, the climate is changing faster than was predicted, mainly because estimates made in previous reports were conservative.

cavedave wrote: »

Nuclear war would pretty much kill everyone I have seen no prediction of climate change that says this will happen. You have to know the costs (or at least the extent) of climate change before any reasonable decisions about how to change our behaviour can be made.

But we are already seeing the effects of climate change. Glaciers are melting and sea-levels are rising. People will suffer as a result, particularly in the developing world where people are more vulnerable. This is not even taking into consideration changes to the climate that are likely to result from, say, the disappearance of the arctic ice-cap. Is this not reason enough to change our behaviour?

cavedave

it doesn't cost anything to turn off a TV rather than leaving it on standby.

Yes it does. If you do this action the ESB require less coal and employees. The TV would (I think) last longer so that some person in Korea might not get employed and someone in Power city would also lose a job. All your consumption decisions from an economic point of view have costs.

Secondly, as you have shown yourself, the climate is changing faster than was predicted, mainly because estimates made in previous reports were conservative.

The current theory (model) that predicts the extent and the causes of climate change is inaccurate to a greater extent then previously allowed for. The theory needs to be made more accurate. I accept that actions need to be taken now rather then wait for a perfect theory.

The question was "Are we responsible for climate change?" and I pointed out deficiencies in the current theory of climate change which is a reasonable thing to do in a scientific discussion.

Is this not reason enough to change our behaviour?

Eh no. Most of the observed melting of Glaciers is believed to be caused by atmospheric smog particles not greenhouse gases. So attempts to limit climate change to help glaciers will have little effect without attempts to limit smog pollution. This is exactly why we need to have a good model of what is causing icepacks and glaciers to melt so we do not spend our resources targeting the wrong problem.

On a side note I am not arguing against anyone here I am looking at the arguments and poking holes in them (I hope). Usually when people realise I am not arguing with them and instead actually looking for the truth they get bored and wander off.

djpbarry

cavedave wrote: »

If you do this action the ESB require less coal and employees. The TV would (I think) last longer so that some person in Korea might not get employed and someone in Power city would also lose a job. All your consumption decisions from an economic point of view have costs.

Now you are being pedantic :rolleyes:. I was obviously referring to the owner of the TV and, besides, you're making a whole raft of assumptions in there.

Besides, who's to say the guy in Power City won't get a better job elsewhere?!?

cavedave wrote: »

The current theory (model) that predicts the extent and the causes of climate change is inaccurate to a greater extent then previously allowed for. The theory needs to be made more accurate.

I accept that the models are not perfect - no model is. But how does one go about making a "theory" more accurate?

cavedave wrote: »

I accept that actions need to be taken now rather then wait for a perfect theory.

My point exactly.

cavedave wrote: »

The question was "Are we responsible for climate change?" and I pointed out deficiencies in the current theory of climate change which is a reasonable thing to do in a scientific discussion.

I never said otherwise, but you are pointing out deficiencies that have already been acknowledged by the scientific community, i.e. they have been accounted for in the latest IPCC report.

cavedave wrote: »

Most of the observed melting of Glaciers is believed to be caused by atmospheric smog particles not greenhouse gases.

If I may draw your attention to the title of this article:

"Polluted haze over Indian Ocean may speed up Himalayan glacier melting"

The net effect of aerosols is to cool the Earth's surface. Most human-produced aerosols come in the form of sulphate aerosols created by the burning of coal and oil. The sulphate aerosols absorb no sunlight but they reflect it, thereby reducing the amount of sunlight reaching the Earth's surface. Besides, sulphate aerosols are believed to survive in the atmosphere for just 3-5 days.

cavedave

Now you are being pedantic . I was obviously referring to the owner of the TV and, besides, you're making a whole raft of assumptions in there.

Besides, who's to say the guy in Power City won't get a better job elsewhere?!?

I am making assumptions to illustrate a point. He might get a job as a pilot because everyone uses all the savings they make from home energy efficiency to pay for an extra holiday every year. My point is that it is very easy to move carbon consumption from one place to another and just saying "put on an extra jumper" might not change the world.

But how does one go about making a "theory" more accurate?

Good question for the science board. Essentially you collect data and pay people whose job it is to make more accurate predictions.

If I may draw your attention to the title of this article:

"Polluted haze over Indian Ocean may speed up Himalayan glacier melting"

Sorry bad link here are many others describing the same smog effect
http://www.latimes.com/news/opinion/sunday/commentary/la-op-garrett7oct07,0,6609252.story?coll=la-sunday-commentary

The net effect of aerosols is to cool the Earth's surface. Most human-produced aerosols come in the form of sulphate aerosols created by the burning of coal and oil. The sulphate aerosols absorb no sunlight but they reflect it, thereby reducing the amount of sunlight reaching the Earth's surface. Besides, sulphate aerosols are believed to survive in the atmosphere for just 3-5 days.

The evidence i have seen does not come even remotely close to proving that these aerosols effect is to cool the Earth's surface. The short half life and western countries ease at removing these pollutants shows why smog should be a concern. They do effect health, they are cheaply removed and they probably effect Glacier melting which has very bad consequences. Here is a pollutant that is relatively easily dealt with that is killing people now and quite likely altering the climate(possibly on a non global scale).

Speaking of half lifes. Methane and nitrus oxide have much shorter atmospheric half lifes then carbon. This means that any reduction we make to these now will have immediate effects on Climate change. Taking up a largely vegetarian lifestyle would drastically reduce our output of these two greenhouse gases. Being a near vegetarian is much easier then not driving a car or going on holiday and only eating locally grown food etc. Yet vegetarianism is rarely advocated as a response to climate change in any advertisement i have ever seen/heard, why?

djpbarry

cavedave wrote: »

He might get a job as a pilot because everyone uses all the savings they make from home energy efficiency to pay for an extra holiday every year. My point is that it is very easy to move carbon consumption from one place to another and just saying "put on an extra jumper" might not change the world.

That is a big leap. I think it is unlikely that someone who is "eco-conscious" enough to make their home more energy efficient is going to make extra flights with the money they save. Besides, a home would have to be extremely energy intensive in order to make those kinds of savings possible.

cavedave wrote: »

Essentially you collect data and pay people whose job it is to make more accurate predictions.

There are already thousands of scientists working in this area. What "people" should we paying who can do a better job?

cavedave wrote: »

The evidence i have seen does not come even remotely close to proving that these aerosols effect is to cool the Earth's surface.

It depends on the type of aerosol. As I have said, sulphates have a cooling effect and they are the predominant aerosol in the atmosphere. However, it is possible that the smog over the Himalayas is mostly caused by the burning of wood and plant matter for cooking in India and other South Asian countries. This would be a unique case - it is unlikely that this would be linked to the melting of ice in the arctic, for example.

cavedave wrote: »

The short half life and western countries ease at removing these pollutants shows why smog should be a concern. They do effect health, they are cheaply removed and they probably effect Glacier melting which has very bad consequences. Here is a pollutant that is relatively easily dealt with that is killing people now and quite likely altering the climate(possibly on a non global scale).

I don't think that anyone is suggesting that smog is not a concern. But, as I have already stated, smog, for the most part, results from the burning of fossil fuels, especially coal. This is all in the IPCC report.

cavedave wrote: »

Taking up a largely vegetarian lifestyle would drastically reduce our output of these two greenhouse gases. Being a near vegetarian is much easier then not driving a car or going on holiday and only eating locally grown food etc.

Good luck trying to convince people, particularly the (highly subsidised) agricultural sector.

cavedave wrote: »

Yet vegetarianism is rarely advocated as a response to climate change in any advertisement i have ever seen/heard, why?

Vegetarianism is strongly advocated, by vegetarians.

bonkey

cavedave wrote: »

I have never written a computer program that did not have any errors. No one I know has ever written a computer program of any reasonable size that did not have any errors. Writing a computer program to simulate a process you do not really understand is unlikely to be accurate.

It depends on what you mean by accurate.

It has to be borne in mind that what these models typically produce is not a single, hard outcome, but rather a range of possibilities, each of which carries a probability of occurrence.

What one typically ends up with in such modelling approaches is a degree of certainty that the outcome will fall within a certain range.

This is designed to mitigate a lot of the uncertainties and errors. It is a well-understood approach which is widely used and is by no means considered unreasonable as an approach. It is not - as you describe it - dodgy to rely on this approach when there is no better alternative available. We have one planet with one climate. Even had we the ability to do so, running full-scale tests is simply not possible. That leaves one thing and one thing only - modelling.

The evidence that climate change is happening faster then predicted shows that our computer models are not accurate.

Yes and no.

It means that between our computer models and our inputs, we have some degree of inaccuracy. It may be, for example, that the models performed in the past underestimated the increases from anthropogenic sources or that we underestimated the effects of those sources. It may be that we have correctly calculated both, and that our model of global warming is bang on target, but that localised effects are inaccurate to a lesser or greater effect.

No-one is even suggesting that even the best models are perfect. What they are saying is that they are sufficiently good to make predictions within certain ranges with certain degrees of confidence.

A simple analagy would be the medical world. If you get diagnosed with a serious condition, your doctor may give you (for example) six months to live if you don't seek treatment tomorrow. In reality, you may live decades without treatment, or it may already be too late for treatment to help you. The treatment may or may not work as expected. The doctor works off a statistical model which gives a a high degree of confidence in predicting a range of outcomes. Any single outcome may or may not buck this model....but that is not a good reason to say that the doctor's model is untrustworthy or dodgy, nor would most people consider it a good reason to go against medical advice.

Simulations that are vastly innaccurate says the unquantified degree is much bigger then previously thought.

This discrepancy has led them to look closer at that specific region to find out what is happening, and the latest research that I've read anything on suggests that other factors specific to the artic have been identified which explain why the artic is not following the trend that the rest of the world is.

Lets not forget that the models predicting global effects are proving incredibly accurate. It is localised effects (such as artic melt) which are at odds with that. Just as a European mini-ice-age shouldn't be confused with a colder world a couple of centuries ago, unexpected artic melt shouldn't be confused with global warming being faster than predicted.

If the theories predictions are inaccurate you have to get another theory.

Or you have to refine your existing one. A theory which matches 90% with observation should not be discarded because it is 10% inaccurate. Rather, the reason for that 10% should be identified, and this then determines whether the model can be adapted/improved, or should be discarded.

Say the climate changes by .0001 degrees is it worth spending 50% of gdp to prevent this?

Say your doctor tells you that you have 6 months to live if you don't have surgery. He admits that there's a chance in a million that you'll survive just fine if you don't bother to have the necessary treatment, and a one-in-a-million chance of the treatment not working in the first place.

What is the smart thing to do? What if its 2 in a million each way, and only permanent disability not death? At what point do you decide that the odds are worth playing? This is the real question with regards to the science of global warming. We have odds, we have impacts, and we have the chance to do something about it.

I would also point out that no-one actually advocating cleaning our act up is throwing figures like 50% of GDP around. Indeed, its champions have been saying for decades that its a goldmine waiting to happen, rather than a moneypit.

Nuclear war would pretty much kill everyone

Nowhere close, but that's not really relevant to the discussion

You have to know the costs (or at least the extent) of climate change before any reasonable decisions about how to change our behaviour can be made.

That's a strange position to take, considering that you argue that modelling the effects is inherently dodgy. It seems that what you're saying is that we need to wait for it to happen before we decide what to do about it....because letting it happen is the only non-dodgy way to know what those costs and extents are.

cavedave

Or you have to refine your existing one. A theory which matches 90% with observation should not be discarded because it is 10% inaccurate. Rather, the reason for that 10% should be identified, and this then determines whether the model can be adapted/improved, or should be discarded.

You need to change the theory, you can call that refine if you want. According to Popper if a theory makes one inaccurate prediction you need a new theory, most scientists would not take it that far though. Also even if you know a theory to be wrong if it is the best one you have you will probably keep using it for the moment.

I would also point out that no-one actually advocating cleaning our act up is throwing figures like 50% of GDP around. Indeed, its champions have been saying for decades that its a goldmine waiting to happen, rather than a moneypit.

my figures were not meant to be accurate I was trying to get across that you need some relatively accurate figures of costs and benefits before you can make decisions.

it seems that what you're saying is that we need to wait for it to happen before we decide what to do about it....because letting it happen is the only non-dodgy way to know what those costs and extents are.

No I am not saying we should let climate change happen on the grounds we do not know everything about it.
You have a fair point about economic models being inaccurate. However economic models have existed for hundreds of years and some expectation of their accuracy is reasonable. If an economist is asked "What will happen to gdp if the temperature goes up 5 degrees?" I would expect an answer that is reasonably accurate given she can probably look at other countries that have this climate.

Lennoxschips

The IPCC made sealevel predictions in 1991, using a combination of empirical data and climate models, for the change in sealevel between 1991 and 2005. Their predictions were absolutely spot on.

gbh

The time for debate is over...now is the time for action...

Maybe the next war America should declare is on Climate Change...then again that would probably ramp up emmissions. I guess we developed nations are so entrenched in a CO2 emmitting life style that there is no way back now.

bonkey

cavedave wrote: »

You need to change the theory, you can call that refine if you want.

I don't care what we call it, as long as we both recognise that inaccuracy neither makes a theory worthless nor beyond redemption.

my figures were not meant to be accurate I was trying to get across that you need some relatively accurate figures of costs and benefits before you can make decisions.

But you also argue that we don't seem to have any means of getting relatively accurate figures. You dismiss the existing models as insufficiently accurate, challenge modelling as a "dodgy" way of getting accuracy in the first place, and offer no alternative.

So if we don't have and cannot get more accurate figures.....what do we do?

No I am not saying we should let climate change happen on the grounds we do not know everything about it.

So what do we do?

If you don't think we should act on our current models, don't accept that models can be reliable, don't offer an alternative to modelling, but don't believe we should sit back and do nothing.....it seems that you want something done, but don't know what. If thats a misrepresentation, then please....tell me what I've misunderstood of your position and what you think should be done (as opposed to what should not be).

If an economist is asked "What will happen to gdp if the temperature goes up 5 degrees?" I would expect an answer that is reasonably accurate given she can probably look at other countries that have this climate.

I'm quite literally speechless that someone who says they have looked at the issue can suggest equating temperature and climate.

cavedave

So what do we do?

I do not know. Pointing out flaws in a scientific theory is a reasonable action. No one should have said "we should ignore inaccuracies in Copernicus's circular orbit model just because we do not know a better theory"

If you don't think we should act on our current models, don't accept that models can be reliable, don't offer an alternative to modelling, but don't believe we should sit back and do nothing.....it seems that you want something done, but don't know what. If thats a misrepresentation, then please....tell me what I've misunderstood of your position and what you think should be done (as opposed to what should not be).

I think we should act on current models. These models have shown themselves to be very inaccurate (more then allowed for in the worst case scenerio of the IPCC report when it comes to Arctic melt). I have made no attempt to suggest what people should do (other then mentioning vegetarianism as a neglected option).

Quote:
If an economist is asked "What will happen to gdp if the temperature goes up 5 degrees?" I would expect an answer that is reasonably accurate given she can probably look at other countries that have this climate.
I'm quite literally speechless that someone who says they have looked at the issue can suggest equating temperature and climate.

Climate and temperature are very closely related. My point is that economic models have shown themselves to be more accurate then climate models to date so basing decisions on them is more warranted.

djpbarry

cavedave wrote: »

Pointing out flaws in a scientific theory is a reasonable action. No one should have said "we should ignore inaccuracies in Copernicus's circular orbit model just because we do not know a better theory"

You make it sound like scientists have no intention of improving models beyond their current state?

cavedave wrote: »

These models have shown themselves to be very inaccurate (more then allowed for in the worst case scenerio of the IPCC report when it comes to Arctic melt).

That is patently not true. This graph is taken from the latest IPCC report:

http://i90.photobucket.com/albums/k243/djpbarry/TempAnomaly.jpg

Global mean near-surface temperatures over the 20th century from observations (black) and as obtained from 58 simulations produced by 14 different climate models driven by both natural and human-caused factors that influence climate (yellow). The mean of all these runs is also shown (thick red line). Temperature anomalies are shown relative to the 1901 to 1950 mean. Vertical grey lines indicate the timing of major volcanic eruptions.

cavedave wrote: »

Climate and temperature are very closely related.

That statement makes about as much sense as me saying "the economy and money are very closely related".

cavedave

That is patently not true

Arctic ice loses are worse then predicted by the IPCC

djpbarry

cavedave wrote: »

Arctic ice loses are worse then predicted by the IPCC

I never said otherwise, but you are suggesting that because this particular result was an underestimate that ALL models used to generate results for IPCC reports are inaccurate, which is not true.

cavedave

because this particular result was an underestimate that ALL models used to generate results for IPCC reports are inaccurate, which is not true.

They probably are. Anyone who has ever programmed up or even played with a daisy world model of climate could tell that*. If the sunlight energy reflected by white sea ice is instead absorbed by dark ocean water your temperature predictions are going to be extremely off.

I should say I do not know enough about the climate to say for certain but I would estimate that Arctic ice plays an important non local positive feedback role in the climate and if you get your predictions on Arctic ice wrong the rest of your models are likely to suffer.

*I appreciate the irony that my sole experience with climate modeling is through simulations and I was the one saying not to rely too much upon them.

bonkey

cavedave wrote: »

These models have shown themselves to be very inaccurate

Take the medical analagy once more. Diagnosis of well-known conditions is generally speaking accurate. There are, however, the occasional patient who's condition progresses massively differently to the diagnosis. In some cases, they inexplicably get better. In other cases, they worsen far more rapidly than expected....often also inexplicably.

When we look at something like this, do we decide that the method of diagnosis is generally accurate given observation matches prediction in the vast majority of cases, or do we decide that its very inaccurate because in isolated cases there is quite literally no correlation whatsoever between the diagnosis and the outcome?

With global warming, you seem to be taking the latter approach. You are taking the sum of predictions of the various models, and then picking one extreme case where they have been significantly wrong, ignoring the multitude of cases where they have been bang on the money.

In fairness to you, you've clarified that you're not suggesting that the patient ignore the doctor's advice....but you are suggesting that the doctor's diagnosis is "very inaccurate", which I simply cannot agree with.

In this case, as in the medical world, when observation and prediction differ so wildly, there is typically a search to find out why. With respect to the Artic melt, there are already additional factors which have been discovered which appear to offer an explanation as to why the discrepancy. Its early days, but science is doing what science should do - its looking at why there is a discrepancy, and how that 'why' can be incorporated into the model.

Climate and temperature are very closely related.

In that temperature is a tiny component of climate, yes. But equal average temperatures have little to do with how alike climates are.

My point is that economic models have shown themselves to be more accurate then climate models to date so basing decisions on them is more warranted.

Leaving aside that I don't share your faith in economic models....you surely have to ragree that one cannot build an economic model of what will happen if the climate changes without knowing what that climate change is.

This is the core problem. Climate-change proponents are saying "X is what is the likely outcome, and we need to look at how to deal with that". Critics aren't saying "let the economists tell us what to do", but are rather saying "we don't accept that X is the outcome".

So what, exactly, can economists base their model on? If they base it on the outcomes predicted by climate change, then those predictions are worthless if the climate-change models are rejected.

Concrete example:

The summer of 2003 caused France to close some nuclear stations periodically, due to a lack of water. Cliamte change predictions say that global warming will lead to increased average temperature in mainland Europe will in turn lead to wetter winters (less snow in the Alps) and warmer summers (more rapid snow-melt, until the snow is gone, plus less summer precipitation), leading (within 20 years) to frequent water-shortages which will make non-coastal nuclear generation problematic.

If the climate-change prediction is right, then we can economically model the impact that this will have. We can look at inland nuclear generation and conclude that within 20 years we need to replace it.

If the temperature-change is wrong, then this outcome probably won't happen.
If the effects of the temperature-change are wrong, then this outcome probably won't happen.

So what do you want the economist to work on? The possibility that Europe will have a regular shortage of water during the summer in 20 years is a prediction of climate change. The economist's cost/benefit of what to do in that scenario is worthless if the climate-change prediction is wrong.

So its not a case of the economist being a better source to go to than the climatologist. The climatologist has to be right before the economist can even enter the game. Once you accept that the climatologist is right...then your argument that the economist's model is more reliable is meaningless.

If what you're trying to say is that if we work from the assumption that the climatologist is right then we should turn to the economist to see where to go....then I'm partially with you. Its not just about economics. Its not about what the cheapest option moving forward is. Its about what the best affordable option is....and economists aren't the ones to decide what constitutes "best".

cavedave

If what you're trying to say is that if we work from the assumption that the climatologist is right then we should turn to the economist to see where to go....then I'm partially with you. Its not just about economics. Its not about what the cheapest option moving forward is. Its about what the best affordable option is....and economists aren't the ones to decide what constitutes "best".

That is what I was trying to say. And i agree that we should not leave all our decisions on what to do about climate change up to economists.

Lennoxschips

cavedave wrote: »

Arctic ice loses are worse then predicted by the IPCC

Difficult to say. It's a long-term model prediction.

Arctic ice may increase again in the mean time (cue sceptics) and decrease again in a sawtoothed pattern, because that's how nature works.

The most important thing I'd take from that IPCC prediction is the overal negative trend towards the year 2100. We'll come back then and see how correct their prediction was. Deal?

It's the same in economics. If an economist predicts a stock market fall of 5% per year untill 2015, he's not wrong if it goes down 10% in the first year. It's a long term prediction. In fact, I'd say that he's a good economist for correctly predicting the direction of a long-term trend.

It is true of course that scientists tend to err to the side of caution in their models, to try and model what knowledge the scientific community knows for sure first. In reality I expect things to me much worse than predicted, but that's my opinion.

djpbarry

Quite a good documentary on BBC 4 last night on the dynamics of ice sheets and glaciers:

http://www.plymouth.ac.uk/pages/view.asp?page=19847

lostinsuperfunk

Like most computer programs, climate models are tested before they are run. Small components can be individually tested (what software engineers would describe as unit tests), e.g. change the surface reflectance, examine the percentage of reflected solar radiation. Is it as expected? The model as a whole can also be tested using historical data. This is more difficult as it seems as the model also is likely to be derived in some way from historical data, leading to a possible redundant self-validation. What I mean is that if you're not careful you end up with a scenario where you derive a model based on some data, then use the same data to test the model. Guess what? It works! However, this problem can be avoided by selecting independent tests. I'm not familiar with climate modelling but certainly this would be regarded as good practice in other physical modelling problems.

cavedave, don't forget about opportunity costs. There is only a finite supply of fossil fuels in the world. We could leave our televisions on 24 hours a day in order to keep Gazprom and the ESB busy and boost demand for red acrylic Power City jumpers (also made from fossil fuels), or we could do something else with all those fossil fuels. For example we could use them to manufacture energy saving insulation materials or provide electricity for LED factories.

Gurgle

Risking a flaming here from the true faithful:
What observed changes in our climate?

Seriously, we are 100% responsible for pollution, deforestation, desertification, wiping out hundreds of species, over-fishing and all that stuff but we can't draw meaningfull conclusions on the cause of climate change without evidence that our climate has actually changed.

lostinsuperfunk

Not flame bait, you'll have to try harder than that

Even most "climate change" sceptics would agree that changes in the climate have been observed in the last 200-300 years. They disagree with the consensus opinion only on the cause of these changes. Climate is constantly changing. For example, we currently appear to be in an interglacial, an abnormally warm period during an ice age. This warm period started long before large-scale burning of fossil fuels by humans. However, the current concern is about the rapid rate of change of surface temperature in recent decades, and its attribution to human activities.

Systematic observations of weather have been made since around the 17th century, and there is also hard evidence of past climate from tree rings, stalactites etc. Check out the IPCC third assessment report, chapter 3, section 3.2.2 on the instrumental temperature record.

AngryHippie

I think resources used combatting climate change are wasted ones. It is probably happening, it is almost certainly as a result of our actions, we should be getting our design engineers to work on systems for water purification, containment, storage and treatment, not just for our happy little current situation, but for some of the worst case scenarios, so that if the outcome turns out to be as bad as Duncan and Gormless are parroting that at least we will have the groundwork done to provide our populations with clean drinking water. Because without it we've got weeks.
I am not talking about a day after tomorrow situation, I am talking about an extended heatwave, leading to a drought, or extended rainfall period leading to flooding of existing water systems with contaminants. To carry on designing urban settlements with the bare minimum requirements by BS codes is short sighted and negligent. not to mention arrogant.