Martin, that is just the point. There is no way to provide direct attribution of an individual event like a death from cancer to its cause. The is no evidence that smoking causes any particular case of cancer, just like there is no evidence that climate change causes any particular extreme weather event. In both cases there is general physical evidence (a carcinogen causing a DNA mutation that is not repaired by the immune system; CO2 causing increased global temperature (field thingy)) but it can never be sufficient for attribution.

We do know that smoking causes cancer - people don't argue against it (unless paid to). So people arguing against attribution of extreme events to climate change are making as much sense as someone who might argue that smoking doesn't cause cancer. If they want to make some sense (which I doubt some do), they should argue that increasing the energy in the atmosphere (hence temperature and humidity) doesn't increase average rainfall and storm intensity. From what little I know that seems unlikely, but it would at least be an honest argument.

geronimo, raff thinks a sample size of n=1, with no controls, makes for good science.

Michael hart

Regrettably n=1 is the number of planets available for the study of anthropogenic global warming.

A parallel unindustrialised Earth is not available as a control. Instead one can use the preindustrial past.

I quite agree with your first two sentences, Entropic Man. That was indeed the point of my comment directed at Raff, who appeared to be trying to draw a false equivalence with the availability of subjects numbering in the many hundreds of millions for tobacco smokers.

Entropic Man, I'll also go a step further and propose a new adage, to be called "Hansen's Law" in honour of the great man himself. After the manner of the Wikipedia definition of Godwin's Law, it could be phrased thus:

Hansen's Law is an Internet adage asserting that "As an online discussion involving at least one global-warming alarmist grows longer, the probability of a comparison involving Tobacco Companies or Cancer caused by Smoking approaches 1"—​that is, if an online discussion about climate and carbon dioxide (regardless of sub-topic or scope) goes on long enough, sooner or later someone will compare someone or something to Tobacco Companies, their apologists, or Lung Cancer caused by Smoking.

Entropic man

Instead one can use the preindustrial past.

Raff who started this thread doesn't like history as a guide. I happen to think it is an excellent guide, often getting getting chastised here for my pains, but do wonder how far back your preindustrial past goes? 200 years? 2 millenia? 20 millenia? Pre-homosapiens? The current warmth doesn't appear to be anything unusual the further back you go, and there is still some way to go in warming to be outside previously experienced levels.

Martin A
How about
There is no CAGW, the only people (researchers) who argue for it are paid to.

SandyS

The Sun is a G2V yellow dwarf star on the main sequence. Its output is gradually increasing as its fuel burns.

To properly consider the long term effect this has had on Earth's temperature you need to think in deep time,up to 5 billion years.

This has implications. The Sun's output was 30% lower when it formed and it is currently increasing at 10%/billion years. All else being equal, for a given CO2 concentration the equilibrium temperature has gradually increased over the last few billion years as insolation has increased.

In terms of human experience, no Homo Sapiens has ever experienced anything warmer than interglacial conditions. The current interglacial peaked at a global average of14.4C according to the proxies, so no human civilisation has ever experieced the current 14.8C, except possibly as a transient peak. The last time sustained temperatures this high occurred was in the pre-Ice Age Pliocene, 2 million years ago.

Entropic man
You're a bit like Raff, very hard to pin down, are you saying that you think we are going to come out of the current glaciation/warmer cycle into permanent warmer than now all thanks to manmade CO2? Or is it that in a couple of billion years the Sun will have warmed us by a similar amount? Is your answer to both that we need to wind things back to how it was in the depths of glaciation? I'm really want to know what you regard as the optimum global temperature should be otherwise you're just putting another we have to reverse climate change into the ring which doesn't move us forward.

The Sun is a G2V yellow dwarf star on the main sequence. Its output is gradually increasing as its fuel burns.

Oh Oh. He's been looking at Wikipedia again.

SandyS

"You're a bit like Raff, very hard to pin down,"

I do bounce around a lot. Perhaps because I delight in complex cause and effect relationships and have broad horizons.

You were asking about timescales. Depending on what I am looking at, my timescale varies from recent weather out to billions of years, and my spatial scale from microclimates to the diameter of the observable universe.

For example, I was just looking at this , the geological temperature record for the past 700 million years.

I was comparing it with the equivalent geoloical CO2 record.

"are you saying that you think we are going to come out of the current glaciation/warmer cycle into permanent warmer than now all thanks to manmade CO2?."

Yes. Look at the geological temperature record. Apart from brief periods at the peak of past interglacials the last time Earth saw sustained temperatures as warm as the present (14.8C) was 3 million years ago in the Pliocene. That was also the last time CO2 was this high.(400ppm)

"Or is it that in a couple of billion years the Sun will have warmed us by a similar amount? "

That is a much more complex question.

At 10%/ billion years the warming effect would be 23.5W/M^2, equivalent to 23.5/3.7= 6.35C/billion years. TheSun would have warmed 7% over the last 700 million years. All else being equal at would have increased surface insolation from 218Wto the current 235W. That is a warming equivalent to 17/3.7= 4.6C.

Over the last 700 million years temperatures have cooled 14C. Clearly insolation is not the dominant effect. From the graph, 700 million years ago CO2 was 20 times higher than the1880 level. That would have produced a temperature difference of 5.35ln(20)*3/3.7=13C.

Put the cooling effect of reduced CO2 , -13C and the warming effect of a warming sun, 4.6C together and you would expect a cooling of -8.4C. Looks as if decreasing CO2 is having more effect than increasing insolation at present.

Unfortunately in the long term our survival is unlikely. Astronomers estimate that the inner border of the habitable zone will move beyond Earth's orbit one billion years hence. At that point our greenhouse effect runs away and we turn into a wet version of Venus.

The Sun is a G2V yellow dwarf star on the main sequence. Its output is gradually increasing as its fuel burns.

Oh Oh. He's been looking at Wikipedia again.

Dec 14, 2015 at 12:33 PM | Unregistered CommenterMartin A

He's coming perilously close to realising that the sun is not a source of "renewable" energy. It is finite.

SandyS

Sorry, the geological temperature record link did not take last time

Martin, I didn't explain well. For both cancer and climate change (in contrast to your evil spirits) there is both cause (with physical evidence) and effect:

1. A carcinogen causing a DNA mutation that is not repaired by the immune system. We know that unchecked DNA mutations can lead to cancer.

2. CO2 causing increased energy in the atmosphere and hence increased temperature and humidity. We know (or at least I propose that we know) that increasing atmospheric temperature and humidity increases average rainfall and storm intensity - there's more energy.

So in lay terms smoking "causes" cancer and CO2 enrichment "causes" increased extreme weather. In neither domain is it possible to attribute any individual event (death from cancer, extreme weather). But in both, the distribution of events has been shifted towards the extreme.

Just as a doctor would probably not (if being careful) say smoking "caused" a cancer, neither would a climate scientist (if being careful) say this storm was "caused" by AGW. But in casual speech that is how it going to come across and a skeptic who wants to argue against this causation has to talk about changes in probability (which many will not understand) or challenge the underlying linkage above.

--

Sandy, you like history, but you don't learn from it. You know that gradual change in forcing might result in sudden environmental change yet you live in peachy Sandyworld where ever tipping point leads towards yet more peaches. Your examples show that civilizations can be brought down by climate changes, yet you refuse to believe that current climate change could be anything but 'excellent!' This failure to consider the possible negatives seems intellectually dishonest, but I assume your reluctance to concede anything to me is due to peer pressure; you can't be blinkered enough not to have considered this privately.

Firstly, if details are important to Raff, then DNA repair mechanisms are primarily intra-cellular, not a function of the immune system. The immune system may change the local environment, encouraging/helping cells to repair themselves, or simply killing the cells in question. Or the immune system may encourage them to kill themselves. Or the cells may kill themselves by apoptosis, with no input whatsoever from the immune system. But the immune system doesn't go inside the cells and repair the DNA.

The Hansen's Law comparison of global warming to lung cancer is a terrible analogy for other reasons too .

The mechanisms by which smoking causes cancer are still poorly understood. This is not surprising, because cancer is considered multi-factorial (i.e. one mutation is not enough), and cigarette smoke is a cocktail of very many compounds.

That some of those compounds definitely may cause direct DNA damage is not worth worth debating. But the link between smoking and cancer wasn't deduced from such 'first principles': It was deduced empirically from observation of cancers in many, many individuals who were observed to be smokers. The attempts at mechanistic explanations came later, and are still on-going.

Catastrophic CO2-caused global warming is the reverse: It has been deduced from 'first principles', but there is no good empirical evidence. The scientific analogy with lung cancer causation simply doesn't fly.

Entropic man,
That's all very interesting but doesn't pin you down any better, you sure you weren't a politician at some point in your life? I was trying to get an opinion from you of what Reversing Climate Change means to you. The phrase as it is used within the CAGW arena seems to mean within a couple of centuries. Or doesn't it matter or is unachievable in that time frame? If it doesn't matter or is unachievable then wasting money attempting the feat would be a waste of money, and more importantly effort when the efforts could be put to much better use in developing solutions, which will be needed whether CAGW exists or not, evidence of natural climate change causing the fall of civilisations that didn't adapt is all around the world. These steps backwards didn't halt the two steps forward made by the rest of the human race unaffected or benefiting elsewhere by the continuously changing global climate.

The typical "life" of a species in the hominid lineage has been 1-2 million years. So naturally dying out within the next million years seems the a more likely fate than frying, boiling or poaching.

SandyS

You want to know what I would regard as an optimum temperature?

Depends what you mean by optimum. I would define it as the temperature at which Earth can support the maximum number of people. On that basis I would suggest somewhere around 13.5 and 14.0C. Go much lower and you lose agricultural land to glaciation, bogs and tundra. Go much higher and you lose land to desertification and rising sea levels.

If the science is correct, we are already committed to 15.5C. Permafrost, clathrate and water feedbacks will probably take us past 16C even if we stopped burning fossil fuels tomorrow. If we carry on as we are we' ll probably pass 17C.

I see no prospect of moving back to my optimum for at least 1000 years. However, since the higher temperatures the greater the damage, it is still worthwhile working to minimise the damage by trying to limit the temperature change.

However, since the higher temperatures the greater the damage, it is still worthwhile working to minimise the damage by trying to limit the temperature change.

Dec 14, 2015 at 4:45 PM | Unregistered CommenterEntropic man

If you went with the original consensus, then it is already too late. And the log-response curve would mean that continued business-as-usual CO2 emissions won't actually make it much worse. So they should focus on adapting, not trying to make people more poor now for less than zero gain in the future.

Of course, at least some of the cognoscenti in the consensus realise that. That is why they keep trying to move the goal posts, always in favour of 'action now' despite innumerable "last chances" coming and going.

Michael hart

I would not rely on the log-response curve. Doubling from 280 to 560ppm CO2 gives a direct forcing of 5.35ln(560/280)= 3.72W/M^2

An ncrease to 1120ppm would produce 7.44W if the response were linear. The log-response produces 7.41W. (

Go all the way to the 6000ppm from 700 million years ago and a linear increase would produce 21W, direct warming. The log-response curve gives 5.35ln(6000/280)=16.4W

Think of global warming damage as like compound interest. Think of saving for a retirement lump sum.A small amount of extra saving early on makes a big difference to the final sum. The later you start, the less you end up with.
For example, £250 a month from the age of 18 nets you £1.2million.
Wait a while.£250 a month from age 30 gives you £480,000., less than half.

The same applies with climate change. Each CO2 molecule not released now avoids more damage than one not released later. The later you start, the harder it is to achieve a given temperature limit.