Geronimo

The full formula is ∆T. = 5.35ln(finalCO2 concentration/initial CO2 concentration)climate sensitivity/watts per C

I was not calculating the effect of a doubling in CO2 with a climate sensitivity of 3. That would be 5.35ln(560/280)3/3.7 giving 3.0C, which you may have been expecting.

Rhoda was asking for numbers to illustrate that the feedbacks associated with CO2 were positive.

To do this I calculated the amount of warming directly due to CO2 forcing from 1880 to the present (280ppm to 400ppm) without taking account of any feedbacks, so I left out the climate sensitivity. I then compared that with the actual warming since 1880 to show that the effect of feedbacks was as large as the direct effect of CO2.

I did indicate this. I mentioned that I was calculating the DIRECT effect of CO2, ie without the feedbacks. I also showed my working.

Supertroll

This whole thread is triggering déjà view!

We have gone over this ground repeatedly and all of us are recycling our old arguments.

Rhoda

You do get an occasional runaway. Snowball Earths were a runaway to a minimum temperature. The PETM may have been a runaway to a maximum only limited by the amount of CO2 in the system.

Most of the time short term perturbations produce little change due to the inertia of a large ocean heat sink. Longer term forcings shift the system from one equilibrium to another. It takes a really big push to produce a runaway warming to either limit.The limits are set by the amount of CO2 available. VWithout CO2 the minimum global temperature is set by solar insolation at about 0C. Dump all the carbon sinks into the atmosphere and the maximum is about 25C.

Supertroll will tell you that the conventional paleoclimate view is that climate tends to settle into five states; snowball Earth around 4C, icehouse glacial around 9C, icehouse interglacial around 14C, hothouse earth around 19C and occasional excursions to 24C.

The difference between a glacial and an interglacial is about 4W (1C) of insolation due to orbital changes amplified to 20W (5C) by an 80ppm increase in CO2 over thousands of years.

Since 1880 we have increased CO2 by 120ppm, Insolation by 4W and temperature by 1C, with more to come. All this took place in 135 years.

That is a bigger, faster push than the climate system has encountered in 50 million years. It will be interesting to see what happens. Your descendants may see a runaway yet.

Mar 11, 2017 at 5:04 PM | Radical Rodent

It is desperately sad that The Royal Society has allowed it's reputation to be tarnished/destroyed. They will need to drain and sterilise their own swamp, to remove all trace of Climate Science Political Pollution.

Being a clever clogs scientist provides no immunity from the stupid gene, especially when exacerbated by politics.

https://en.m.wikipedia.org/wiki/John_Desmond_Bernal

EM, whenever the IPCC is mentioned at Bishop Hill, there will be deja vu, as you still assume that what the IPCC has stated, is fact.

I do not claim to be a Scientist, whereas you do. Is there nothing about Hockey Teamster Science, the IPCC and their inability to find mistakes, that does attract your curiosity?

EM: "Since 1880 we have increased CO2 by 120ppm, Insolation by 4W and temperature by 1C, with more to come. All this took place in 135 years."

I think it would be less controversial to say: Since 1880, CO2 has increased by 120ppm, theory says that back-radiation has added 4W and temperatures are 1C higher. but let's move on.

By your own figures which you offered a short while back in January, "...IIRC the change in radiating height since the 1880s is 5 hectopascals, equivalent to 45m. That accounts for 100* 45/110=41% of the 1C observed warming. The remaining 59% comes from downwelling [back] radiation...

I can accept the observable 0.41degC of warming since 1880: GE effect is 33degC which is now 33.41degC. So we have, by your figures, a missing 0.52degC of warming which has been produced by a 4W augmentation of insolation. The supporting evidence for that being an hypothesis that shows the missing 0.52degC to be calculable (not getting into the subject of historical global temperatures as support) but not evident.

That missing 52% is nevertheless retained in calculations of climate sensitivity which suggest our descendants may see a runaway atmospheric temperature.

I see a problem with that, no?

EM

1. The IPCC equation for ECS is: ∆T = lambda x RF

where lambda is the climate sensitivity and RF = 5.35 x ln(C2/C1) where C1 and C2 are the levels of CO2 in the atmosphere at the beginning and end of the period respectively.

If you take the sensitivity out of the equation the temperature rise caused by an increase in CO2 from 280ppm to 400ppm should be 1.9C shouldn't it?

2 "I don't know why you think that climate scientists do not know about equilibrium." I don't think climate scientists don't know about equilibrium. The point of my post was to try to ascertain what the actual mechanisms are in the Earth's climate system which will allow a rise in temperature of, say 3C, and then stop at that level. As rhoda as pointed out earlier the climate system just recognises heat, it can't differentiate between CO2 heat and any other kind of heat.

So the scientists are saying if we get to 1.2C (doubling of CO2) the climate will continue warming until it reaches 1.5C to 4.5C, which is the ECS, my question, clearly clumsily put, is what changes in the climate system at these temperatures to stop it going into an uncontrolled positive feedback loop.

Which leads me to ask if this phenomenon can be observed in the climate optima of the holocene?

EM and others who fall back on the claim that their interpretation of how climate responds to CO2 are falling back on the same fallacy the eugenics defenders relied on in claiming that since evolution is sound science, eugenics must be real.

As many have pointed out, positive feedbacks are generally indicative of an unstable system. It goes out of control.

Stability is indicative of negative feedbacks. Our climate is remarkably stable.

There is nothing magic about CO2. If water vapour was prone to positive feedback, then any reason for warming could cause evaporation, more warming and catastrophe. But it never does. Water vapour has many tricks, including latent heat of phase change, cloud formation to reflect sunlight, and radiation to space to lose heat. The feedbacks are mainly negative.

Our climate is stable enough to have supported life for thousands of years. Our temperature has varied considerably, but has never gone out of control.

Carbon dioxide traps radiant heat in the troposphere, particularly in the tropics where solar heating of the surface is greatest. So the theory goes. But the predicted hot spot has never been found, despite satellites and weather balloons searching for it for decades. Where is it?

The carbon dioxide molecules, excited by received photons, collide with other molecules and transfer their kinetic energy. Among thos molecules receiving energy are water vapour molecules and these can radiate heatto space. Water vapour in these circumstances give negative feedback and explain why runaway global warming is bol**cks.

Martin A

I beg your pardon. Wrong CO2 emission line.

Early infrared seekers were most effective in detecting infrared radiation with shorter wavelengths, such as the 4.2 micrometre emissions of the carbon dioxide efflux of a jet engine.

Why can't you show the actuals? The change in water vapour. Some actual thing, not supposition.

That a warmer atmosphere can (and therefore will) hold more water vapour and that water vapour is a powerful greenhouse gas is pretty uncontroversial, further, the increased humidity has been observed and found to be in line with the models…

 Between 2003 and 2008, the global-average surface temperature of the Earth varied by 0.6°C. We analyze here the response of tropospheric water vapor to these variations. Height-resolved measurements of specific humidity (q) and relative humidity (RH) are obtained from NASA's satellite-borne Atmospheric Infrared Sounder (AIRS). Over most of the troposphere, q increased with increasing global-average surface temperature, although some regions showed the opposite response. RH increased in some regions and decreased in others, with the global average remaining nearly constant at most altitudes. The water-vapor feedback implied by these observations is strongly positive, with an average magnitude of λq = 2.04 W/m2/K, similar to that simulated by climate models. The magnitude is similar to that obtained if the atmosphere maintained constant RH everywhere.

Dessler et al 2008

The conclusion section of the same paper observes that

The existence of a strong and positive water-vapor feedback means that projected business-as-usual greenhouse-gas emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius. The only way that will not happen is if a strong, negative, and currently unknown feedback is discovered somewhere in our climate system.

I, for one, do not feel that lucky. For further observations check out Brian Soden's paper, he measured the reduction in water vapour that occurred when the planet was cooled by the fallout from the Mt Pinatubo eruption and found that by comparing model simulations with and without water vapor feedback, we demonstrate the importance of the atmospheric drying in amplifying the temperature change and show that, without the strong positive feedback from water vapor, the model is unable to reproduce the observed cooling.

Geronimo
There is one big negative feedback which kicks in as temperatures rise.

Increasing CO2 decreases OLR in the 13-17 micrometre range. Feedbacks include a decrease in OLR across the black body spectrum due to extra water vapour and a reduction in albedo due to ice melt. The overall result is an imbalance between Insolation and OLR The energy accumulating due to that imbalance causes the surface rface temperature increase.

The surface also radiates more energy as the temperature rises. This increases OLR. and cancels some of the effects of increasing CO2. As temperatures rise, so does OLR until a new equilibrium emerges.

This Stephan-Boltzmann radiation increase is potentially llarger than the change due to the stronger greenhouse effect. It damps further warming and stops it running away.

Thanks Phil, but my question is simple and disingenuous. What stops the climate going into a "POOF" (h/t Martin A), when temps go to 3C+?

Geronimo

Did you read my 10.07pm?

Increasing surface temperature increases Stephan-Boltzmann black body radiation which increases OLR.

Increasing surface temperature increases Stephan-Boltzmann black body radiation which increases OLR.

Mar 12, 2017 at 11:43 PM | Entropic man

How does Stephan-Boltzmann explain the pause/hiatus of Global Warming?

There is no Climate Science to convince Trump that he should continue wasting US Taxpayer Funding on it, let alone evidence of a positive feedback, to continue scaring people with.

PC the strong positive feedback is bunk. If there was a strong positive it would have triggered before. Your persistence in clinging to it is not making you look clever.

EM, I am not picking on you, but I will use this if you do not mind...

"You do get an occasional runaway. Snowball Earths were a runaway to a minimum temperature. The PETM may have been a runaway to a maximum only limited by the amount of CO2 in the system.

Most of the time short term perturbations produce little change due to the inertia of a large ocean heat sink. Longer term forcings shift the system from one equilibrium to another. It takes a really big push to produce a runaway warming to either limit.The limits are set by the amount of CO2 available. VWithout CO2 the minimum global temperature is set by solar insolation at about 0C. Dump all the carbon sinks into the atmosphere and the maximum is about 25C.

Supertroll will tell you that the conventional paleoclimate view is that climate tends to settle into five states; snowball Earth around 4C, icehouse glacial around 9C, icehouse interglacial around 14C, hothouse earth around 19C and occasional excursions to 24C."

These are assumptions. Many people may think they are the best there is. Fine.

So the let's assume for arguments sake, that you first model the system blind.

The models are iterative. They feed themselves. And there will be a number of runs that will run away.

So what happens? "Ahhh, if we look at the above assumptions those run aways are likely wrong." So they tweak and coalesce around "acceptable" ranges.

But... the "run away" runs are just as valid as those that "look right". i.e. they are all just as invalid or valid. Just because it looks right, doesn't mean it is right.

It is no different than people doing the lottery and thinking [1 7 18 38 46 50], has more chance than [1 2 3 4 5 6].

Ahh but the system isn't random? But what do we know from an imperfectly measured, 30 year time slice out of billions of years.

Take one further step back. Global Mean Temperature? What real meaning does it have?

If it was called the Global Climate Chaotic Factor, which is was it is, would the science be treated differently? Of course it would. This number is produced, but do we really know what it means?

I have no issue with any of this work. But to claim it is settled science it is just a travesty to science.

If you do not start then you never get anywhere, but we are at the first station not the last.

Geronimo has asked about sensitivity feedbacks.

Here is how I would describe our knowledge of Climate Sensitivity...

It is like a game of Chinese whispers between God and the Scientists.

God whispers in the climate scientists ears the Climate Program. Millions of lines of code, thousands of Classes, millions of threads running and interacting in parallel.

After it goes around the table at the Climate Scientist's common room, the last Scientist writes this up on the white board..

Print "Hello Word, it will get warmer, probably\n";

Geronimo,

CS is expressed as the warming that occurs due to a radiative imbalance (net forcing) once equilibrium has been reached. It is normally expressed in degrees C per doubling of CO2.

So let us assume CS is 3C, a rise from 250ppm to 500ppm gives a warming at equilibrium of 3C, but the next 3C requires a rise to 1000ppm. As EM points out the forcing prouduced is proportional to the log of concentration. At the concentrations and temperatures we are at now, the amplifying feedbacks produce a roughly linear response.

As EM also observed, the outgoing half of the radiation picture is governed by the Stefan-Boltzmann equation. This states that the radiation from a black body is proportional to the fourth power of its absolute temperature ( the Earth is not a black body but near enough for the law to apply).

So as concentrations rise, the forcing response is (roughly) linear, but as temperature rises the outgoing radiation rises according to a power law, hence at some point the inward and outward fluxes will be in equilibrium. No runaway.

FACTS few of us disagree with: 
1. the rise in CO2 has been more or less steady since the turn of the 19th century; 
2. the human consumption of fossil fuels has risen exponentially over the same time period such that, so far, in the 21st century, we have burned more than 30% of all the fossil fuels burned to date. Yet CO2 concentrations continue to rise at the same rate as during the 19th century;
3. since the turn of the 20th century, there have been just under 60 years of warming; the remaining years have seen temperatures steady, or declining;
4. correlation is NOT causation..

1. More or less, we have direct observations since the fifties, before that .... proxies?

https://en.wikipedia.org/wiki/Keeling_Curve

2. Fossil fuels are valuable commodities, so we have good accounting records. Thus we can estimate with reasonable accuracy how much CO2 has been emitted. If it had all remained airborne, concentrations would be approximately twice what we observe. The excess has been absorbed by natural sinks, mainly the biosphere, causing 'greening' and the oceans, causing acidification. The rate at which the planet provides this valuable service varies.

Then there's the fact that the isotopic signature of CO2 that originated from fossil fuel combustion differs from that from other sources. Nothing to do with the Cat in the Hat, but google the Suess Effect.

All of the increase is manmade. 

3 Number of years rising/falling/unchanged is a bizarre metric. The surface is about 1C warmer than it was in 1900.

http://www.woodfortrees.org/plot/hadcrut4gl/from:1900/trend/plot/hadcrut4gl/from:1970/trend/plot/hadcrut4gl/mean:12/from:1900

4. Indeed not. But check this.. (Or just Fig 10.5 if you're pushed for time).