Whenever I hear those that deny anthropogenic global warming, they often talk about how climate science is predicated upon a bunch of 'assumptions' that are untenable. What are these assumptions and what do they actually mean, and why do they invalidate scientifically climate science?

Thanks Soren, I am actually directing this at the skeptics on this board, but it would be good to see some input from non-skeptics too.

Soren wrote on Nov 11^th, 2010 at 1:18pm:


Come on Soren, you'll have to do better than that. What are you sceptical about with respect to Al Gore?

- his existence?
- his credentials as a communicator?
- the colour of his tie?
- his taste in food?
- the fact that his eyes are too close together?

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Every time I try to explain this, you either go silent or say something like (paraphrased) "Sorry, I'm not convinced" without explaining exactly which part you had issues with.  - or was it more a case of

- "Oh it's all too complicated for me to understand therefore nobody could possibly understand this because I'm smarter than everybody else" ?

Maybe it's your philosophical background talking when you said once  (paraphrased) "There are no answers - only questions"

Well that's it then, we might as well all give up. Technology is a figment of our imaginations because Soren says it's too hard, and no questions can be answered.

The point is that you haven't attempted to understand the explanations and evidence that has already been profferred.

If all scientists suddenly became philosophers, the world would be like Monty Python's soccer match, with everybody agonising about the first move.

Weather forecasting is a great deal more complex than forecasting the temperatures and average rainfalls 50 years from now.

Regardless of that, I've been using a publically available weather forecasting model for the last 3 years that has been very accurate for rainfall prediction up to a week in advance.

Certain aspects of climate are much easier to get right than that, and relatively primitive models developed in the 1980's have largely predicted the last 25 years with remarkable accuracy. Currently we are into 4th generation climate models which now include ENSO and Solar cycle data.

We can use past recurring patterns and superimpose the effects of an average increase in Global temperatures.

If you put it very simply, increasing greenhouse gases decreases the Long Wave Infrared radiation to space, and increases the net energy of the lower atmosphere.

If you have a stepwise increase in the amount of energy going into a system (any system) you will see some kind of change.

That change can manifest itself in terms of increased temperature or the energy can be expended elsewhere (eg wind). Either way, we'll see a change.

We know how much greenhouse gases we are emitting (accountants make sure this information is accurate because of the $$$ that change hands).

We can see the effects of increasing CO2 on ocean pH and the effects this will have on a great many economically important species.

Regardless of whether it will happen in 2035 or 2060, the glaciers of this world are decreasing in size and will continue to do so, barring a super volcano erupting or something else that has not happened in the past 70,000 years or so.

The implication of the reducing size of glaciers, such as the himalayans are changes in regional climate (eg monsoons) and reduction in floodwaters.

For weather, this is an excellent precipitation model:

http://www.bom.gov.au/australia/charts/viewer/index.shtml

The financial pressures associated with business are even more complex than global climatic data, yet even there, we don't throw our arms up in the air and say "It's all too difficult"

We work on the best data we can get, and in the case of climatology that data is making some predictions which have not substatially changed (except in terms of increasing magnitude) since the mid 20th century.  

It comes down to the fact that for these high risk consequences, only a fool, or Christopher Monckton (on second thoughts,  'only a fool' says it all) would subscribe to the do-nothing option.

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I have heard similiar arguments employed against the usage of heritability analysis as well. You are demanding predictions made with near absolute certainty, and this requires a model that is a totally immaculate replication of actual climate as it exists in the real world. I thought that science was supposed to be probabilistic, and where absolute certainty cannot be established (if it can truly ever be established) we have to reply on reductionist approaches where the available models which are the most predictive of actual phenomeona with the highest probability are selected as the most favoured models. Am I off or is this supposed to be the argument Muso has always tried to make?

gizmo_2655 wrote on Nov 12^th, 2010 at 3:21pm:


Did you pull those figures regarding the inaccuracy of future climate prediction (long term climate) based on current climate models and trend projections out of your arse or do you have anything to back that up?

In other words, weather is what is actually happening while climate is statistics of what has happened.

Weather is what we actually experince. We do not experience climate.

Soren wrote on Nov 12^th, 2010 at 10:39pm:


What was the temperature yesterday where you live? Was that a minimum a maximum or a mean temperature?

Everything is statistical about weather and climate. If you are saying that weather is somehow the instantaneous weather, then you're barking up the wrong tree. Weather is short term (high resolution), climate is long term(low resolution), and both have to be qualified in some way before they make sense. What was the barometric pressure in Queensland yesterday? What was the wind speed in Sydney yesterday. You might qualify those answers by giving a range. Apart from the past weather, you can provide a weather forecast. These are usually very accurate these days, but you can never say something like "There will be a sudden gust of wind in Paramatta tomorrow at 1:38"

 

The reason I asked you to define what you meant by statistics was not rhetorical. I wanted to know what you were really trying to say - that is if it's your original idea in the first place. Maybe you need to refer back somewhere to find out what it says your opinion is.

Didn't you understand the analogy I gave of the paper boat?

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The main population of Inuits in Alaska would take you to task if you tell them that they didn't experience the changing climate of the last 50 years.

Soren wrote on Nov 13^th, 2010 at 8:16am:


In order to make sense out of anything, you need to apply some kind of statistical technique, even if it's just a total.

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The paper boat - It's a point of reference. That's all. It is impossible to describe position in that example without a point of reference, but I see that you understand the inference.

In terms of the groupies, the eccentrics, that's a hat that fits your own point of view.

In terms of the people who actually practice this science, I'm not telling you anything any more controversial than atmospheric physics. That's a pretty dry subject and physicists tend to be the most conservative of all scientists.
http://www.abelard.org/briefings/global_warming_atmospheric_chemistry_physics.ph...

There is a pretty useful spectrum on that site which I'll reproduce here. It clearly shows how Greenhouse gases absorb LW IR radiation. Which common atmospheric gases are absent from that diagram, and why?

Soren wrote on Nov 14^th, 2010 at 3:55pm:


It's  an analogy. The position if the boat represents where we are at any given time. We can get a broad picture of where the boat is located at any given time quite easily by using some fairly simple calculations.

Once you narrow in on the position of the boat a higher resolution, the mathematics becomes more difficult - ok?

Let's drop it, because you clearly understand the difference.

Most climatic data is averaged over at least a 20 year period. If we take the temperature maps for Australia, you'll find very little difference over the last 50-100 years. For example:



and



As you can see - not much difference. Maybe a bit of an increase in most areas.  So blind Freddy can see that it's relatively easy to predict reasonably accurately what that chart will look like in another 20 years given a relatively steady state scenario.

No complex models needed.

However, if you try to predict what the precipitation in in Bankstown next Sunday, it's a far more difficult thing to do.

Given that we're talking about average global temperatures and precipitations, the argument that it's incredibly complex becomes silly.

Another analogy is predicting the shape of an baby elephant when it grows to adulthood. I think we agree that we could make a reasonably good prediction of that, however predicting the shape of the wrinkles in its skin would be extremely difficult by comparison.

High resolution=  weather; low resolution = climate.  

Soren wrote on Nov 14^th, 2010 at 9:35pm:


It's possibly a dry subject to those who can't follow scientific principles.

Now do we agree that CO2 is a greenhouse gas? Certainly without CO2 the planet would be much cooler, so it follows that it is a greenhouse gas. If we reduce the amount of CO2, the planet gets cooler (and I already brought up the mechanism - LW radiation etc).

If we increase the CO2, the planet gets warmer. The relationship is logarithmic.

The one that's usually proposed is injecting sulphates into the upper atmosphere using commercial jets.

My own perspectives on this are:

1. It would certainly result in a cooling effect, but would probably be more expensive than transitioning to carbon neutral technologies - and that's something we'll be forced to do anyway (in the case of oil) as demand for oil exceeds supply.  Maybe we'll need to do that as a last resort.

2. It would do nothing for Ocean acidification. We'll still be faced with decreasing calcification in many economically important marine organisms.

In terms of using oil for fuel, we're in great danger of depleting supplies of coal and oil for the manufacturing of petrochemicals, including plastics. Oil should be used for that purpose while we still can, so there is a great advantage in maintaining coal and oil reserves.