Tag: prediction

Modelling the future.

Can we trust the predictive output of computer modelling?

I would be the first to admit that this is not an area where I have anything more than general knowledge.  However, what prompted me to think about this topic was a chance conversation with someone here in Payson.  We were chatting over the phone and this person admitted to being less than fully convinced of the ’cause and effect’ of man’s influence on the global biosphere.

When I queried that, what was raised was the idea that all modelling algorithms used in climate change predictions must incorporate mathematical constants.  I continued to listen as it was explained that, by definition, all constants were, to some degree, approximations.  Take, for example, the obvious one of the constant π, that Wikipedia describes as: a mathematical constant that is the ratio of a circle’s circumference to its diameter. Pi, of course, would have to be rounded if it was to be used in any equation.  Even taking it to thirty decimal places, as in 3.14159 26535 89793 23846 26433 83279, would mean rounding it to 3.14159 26535 89793 23846 26433 83280 (50288 being the 30th to 35th decimal places).

OK, so I must admit that I was leaning to the viewpoint that this person had a valid perspective.  I then asked Martin Lack, he of Lack of Environment and a scientifically trained person, for his thoughts.  The rest of this post is based on the information that Martin promptly sent me.

One of the links that Martin sent was to this post on the Skeptical Science blogsite.  That post sets out the common skeptics view, namely:

Models are unreliable
“[Models] are full of fudge factors that are fitted to the existing climate, so the models more or less agree with the observed data. But there is no reason to believe that the same fudge factors would give the right behaviour in a world with different chemistry, for example in a world with increased CO2 in the atmosphere.”  (Freeman Dyson)

The author of the Skeptical Science posting responds,

Climate models are mathematical representations of the interactions between the atmosphere, oceans, land surface, ice – and the sun. This is clearly a very complex task, so models are built to estimate trends rather than events. For example, a climate model can tell you it will be cold in winter, but it can’t tell you what the temperature will be on a specific day – that’s weather forecasting. Climate trends are weather, averaged out over time – usually 30 years. Trends are important because they eliminate – or “smooth out” – single events that may be extreme, but quite rare.

Climate models have to be tested to find out if they work. We can’t wait for 30 years to see if a model is any good or not; models are tested against the past, against what we know happened. If a model can correctly predict trends from a starting point somewhere in the past, we could expect it to predict with reasonable certainty what might happen in the future.

So all models are first tested in a process called Hindcasting. The models used to predict future global warming can accurately map past climate changes. If they get the past right, there is no reason to think their predictions would be wrong. Testing models against the existing instrumental record suggested CO2 must cause global warming, because the models could not simulate what had already happened unless the extra CO2 was added to the model. All other known forcings are adequate in explaining temperature variations prior to the rise in temperature over the last thirty years, while none of them are capable of explaining the rise in the past thirty years.  CO2 does explain that rise, and explains it completely without any need for additional, as yet unknown forcings.

I strongly recommend you read the full article here.  But I will republish this graph that, for me at least, is a ‘slam dunk’ in favour for modelling accuracy.

Sea level change. Tide gauge data are indicated in red and satellite data in blue. The grey band shows the projections of the IPCC Third Assessment report (Copenhagen Diagnosis 2009).

Not only does this show that the data is within the range of projections of the modelled output, more seriously the data is right at the top end of the model’s predictions.  The article closes with this statement:

Climate models have already predicted many of the phenomena for which we now have empirical evidence. Climate models form a reliable guide to potential climate change.

There is a more detailed version of the above article available here.  Do read that if you want to dig further down into this important topic.  All I will do is to republish this,

There are two major questions in climate modeling – can they accurately reproduce the past (hindcasting) and can they successfully predict the future? To answer the first question, here is a summary of the IPCC model results of surface temperature from the 1800’s – both with and without man-made forcings. All the models are unable to predict recent warming without taking rising CO2 levels into account. Noone has created a general circulation model that can explain climate’s behaviour over the past century without CO2 warming. [my emphasis, Ed.]

Finally, back to Lack of Environment.  On the 6th February, 2012, Martin wrote an essay Climate science in a nut fragment.  Here’s how that essay closed:

Footnote:
If I were to attempt to go even further and summarise, in one single paragraph, why everyone on Earth should be concerned about ongoing anthropogenic climate disruption, it would read something like this:

Concern over anthropogenic climate disruption (ACD) is not based on computer modelling; it is based on the study of palaeoclimatology. Computer modelling is based on physics we have understood for over 100 years and is used to predict what will happen to the atmosphere for a range of projections for CO2 reductions. As such, the range of predictions is due to uncertainty in those projections; and not uncertainties in climate science. Furthermore, when one goes back 20 years and chooses to look at the projection scenario that most-closely reflects what has since happened to emissions, one finds that the modelled prediction matches reality very closely indeed.

In his email, Martin included these bullet points.

  • Concern over anthropogenic climate disruption (ACD) is not based on computer modelling.
  • It is based on our understanding of atmospheric physics (and how the Earth regulates its temperature).
  • Computer modelling is based on this physics (which we have understood for over 100 years).
  • Models have been used to predict temperature and sea level rise for a range of projections for CO2 emissions. 
  • The wide range of predictions was due to uncertainty in those emissions projections not uncertainties in climate science. 
  • This can be demonstrated by looking at predictions made over 20 years ago in light of what actually happened to emissions.
  • The model predictions for both temperature and sea level rise are very accurate (if not slightly under-estimating what has happened).

Sort of makes the point in spades!  The sooner all human beings understand the truth of what’s happening to our planet, the sooner we can amend our behaviours.  I’m going to pick up the theme of behaviours in tomorrow’s post on Learning from Dogs.

Finally, take a look at this graph and reflect!  This will be the topic that I write about on Thursday.

The Role of Fear

Fear of the Known – thinking aloud about stuff

Jon Lavin wrote a Post on the 13th June, 2010 entitled, “Dealing with the fear of the known.” I’ve been thinking about that in recent weeks including the comment to Jon’s article from Per. Here’s how Jon closed that article:

If more of us got used to coming out of the mind before making an important decision, and simply sat with the question for a while, the answer would probably present itself.

This will probably raise more questions than it answers but that’s not a bad thing.<!–

And here’s the recent comment from Per: Great advice… but how do we remove the fear of what is known?

Presumably Per was implying that we shouldn’t fear the known. However, I beg to differ here; it is actually fear of the UNKNOWN that is rather pointless (I am not afraid of aliens), while fear of the KNOWN is CRUCIAL to our survival.

But like anything else, you can have too little or too much. Too little, and you survive a very short time. Too much, and you sit cowering in your cellar afraid to go out. As with EVERYTHING in life it is a question of BALANCE.

How do we know how much fear to deploy? Instinct, intelligence, knowledge and experience. If any of these are deficient, we may apply an inappropriate fear quotient.

Let’s take “Global Warming”! How afraid of it should I be? What are my marks out of 10 for the four fear-factors above?

Instinct = 8 – I instinctively fear a situation when my environment is getting hotter, as I don’t know what that will imply.
Intelligence = 8 – I am (just) intelligent enough to appreciate the dangers of a rise in temperature.
Knowledge = 4 – I have no real idea exactly what is going on or how far it will go; the messages are mixed and I see no real panic among governments.
Experience = 0

So, a score of just 20 out of 40, which means IGNORANCE and DOUBT and these add up to FEAR ….. so I am quite afraid.

Home grown vegetables

More apparently, than my leaders seem to be, who can’t even ban flying across the Atlantic at a cost of 60,000 tons of CO2 per day. The question is, will this considerable amount of fear push me into actually DOING something about GW? What is my inertia level and what is my tipping point? What would it take to get me to dig up my garden and plant potatoes? To sell my car and buy a horse? Sadly, humans are in general pretty inert …… it is much easier to do nothing or too little until it is (almost) too late.

So, “fear” is absolutely essential to our survival. If you’re a driver who doesn’t fear accidents then please keep out my my way until you very soon die in one.

Fear is also what pushes me to drive very carefully. People who greedily lent money to Madoff had no fear they would lose it, having lost all control of  whatever ration of commonsense and/or logic they might once have had. Perhaps now people will fear rather more about losing their money and therefore invest it more wisely.

To take another topical example, any company in the future (is there one?) drilling for oil in the Gulf of Mexico will fear the lash of Obama’s tongue and stick and this fear will push them to be a bloody sight more careful and to have an effective contingency plan. Actually, why more people don’t have a lot more fear is a mystery to me.

Right, having dealt with fear, we come to our response to it, which is of course the interesting bit. The world is changing so fast that almost all of us have limited control. Even the US President has limited control. This is not comfortable.

How then can we gain more control and become more comfortable? Jon has pointed the way; we must become more self-reliant. Jon will presumably now have much less fear of starving to death, since he is producing a proportion of his own grub. Anyone installing solar-panelled heating will be much less fearful about their electricity being cut off.

I would go further. Anyone owning a horse will or would have much less fear about running out of fuel and being immobile – or more to the point, of being unable to plough and sow his fields, without which we really are stuck. (Incidentally, I am predicting a big comeback for work horses. They are slower, yes, but you can’t breed a tractor (or indeed talk to it) or produce your own fuel, which is where the horse wins out. We’ll have to move more slowly, but then speed is vastly overrated.)

Now Jon with his chickens is a special case. Is there, I wonder, a small element of “fear” in his decision to keep chickens? Humans are complex …. Another major factor pushing Jon down this road could be (and in his case probably is) social responsibility.

It seems pretty clear that if EVERYONE became more self-reliant then vast, expensive, high-consuming centres  of production would be scaled down. Unfortunately, social responsibility is not exactly fasionable in today’s consumer world (or we wouldn’t use plastic bags for a start, just to take one small example). Like the vegetarians of 30 years ago, Jon might be seen as an exception if not crank; until of course the fear factor becomes higher and then everyone will try to grow their own potatoes.

So, fear of powerlessness drives us to take initiatives that will help to remove at least some of this fear; a circular but inevitable process.  Nothing new about it; the only sad thing is that humans seem to need to travel quite a long way down the path of doom before they really start to react.

This of course is why we did nothing when Hitler invaded the Rheinland in 1936; wait and see seemed easier at the time. It’s also why America totally ignored Jimmy Carter’s ideas of some decades ago about reducing America’s dependence on Arab oil. It was much easier to deride him and do the easy (but totally wrong) thing, especially of course as the oil companies have loads of money and can buy off people who otherwise might see the light.

Well, we’re well past “Wait-and-see” now …… we are now entering the “Do-it-or-else ….” period. And where Jon is of course achieving a double-whammy is that his increasing self-reliance is also GOOD FOR SOCIETY. If everyone were more self-reliant in every way a vast saving in energy and everything else could be achieved. Flying exotic fruits into Britain from South Africa is insane, yet so normal that it seems … errrmmmm … normal.

All this was obvious years if not millennia ago, but the current state of the world has increased the fear factor and is pushing people like Jon down this road. But it is an interesting road. Being self-reliant has multiple advantages, though it will be pretty hard on the rich, who may have to learn how to do things they usually pay underlings to do.

But Jon is in the vanguard of this movement; there is VAST scope for increasing self-reliance. It could and should be an adventure, though it will involve enormous change.  The latter of course can also be stressful, but less so when it is clearly a change for the better, as I believe it will be.

By Chris Snuggs