Climate Alarmism

[_MeDotOrg]

One of the things that is difficult to calculate for the future are the negative feedback loops that will occur as global warming continue. For example, as permafrost melts, large amounts of methane are released. Methane helps trap heat. The planet gets warmer, melting more permafrost, releasing more methane. Another negative feedback loop: as the area of the freeze line marches further towards the poles, insect populations that had been previously held back by freezing temperatures now march forward into virgin forests that have no defense mechanisms against the insects.

Personally I think every member of the House and Senate should be required to write a letter to the first American child born in the 21st Century, telling that person why you thought there was or wasn't man-made climate change, and what guided your decision making process.

[_Gunnar]

MeDotOrg, what you just described is a positive feedback loop, not a negative feedback loop.

Positive feedback is a process that occurs in a feedback loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation.[1] That is, A produces more of B which in turn produces more of A.[2] In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback.[1][3] Both concepts play an important role in science and engineering, including biology, chemistry, and cybernetics.

Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect.[1][3] That is, positive feedback is in phase with the input, in the sense that it adds to make the input larger.[4][5] Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there will typically be exponential growth, increasing oscillations, chaotic behavior or other divergences from equilibrium.[3] System parameters will typically accelerate towards extreme values, which may damage or destroy the system, or may end with the system latched into a new stable state. Positive feedback may be controlled by signals in the system being filtered, damped, or limited, or it can be cancelled or reduced by adding negative feedback.

Positive feedback is used in digital electronics to force voltages away from intermediate voltages into '0' and '1' states. On the other hand, thermal runaway is a type of positive feedback that can destroy semiconductor junctions. Positive feedback in chemical reactions can increase the rate of reactions, and in some cases can lead to explosions. Positive feedback in mechanical design causes tipping-point, or 'over-centre', mechanisms to snap into position, for example in switches and locking pliers. Out of control, it can cause bridges to collapse. Positive feedback in economic systems can cause boom-then-bust cycles. A familiar example of positive feedback is the loud squealing or howling sound produced by audio feedback in public address systems: the microphone picks up sound from its own loudspeakers, amplifies it, and sends it through the speakers again.

A simple negative feedback system descriptive, for example, of some electronic amplifiers. The feedback is negative if the loop gain AB is negative.
Negative feedback (or balancing feedback) occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances.

Whereas positive feedback tends to lead to instability via exponential growth, oscillation or chaotic behavior, negative feedback generally promotes stability. Negative feedback tends to promote a settling to equilibrium, and reduces the effects of perturbations. Negative feedback loops in which just the right amount of correction is applied with optimum timing can be very stable, accurate, and responsive.

Negative feedback is widely used in mechanical and electronic engineering, and also within living organisms,[1][2] and can be seen in many other fields from chemistry and economics to physical systems such as the climate. General negative feedback systems are studied in control systems engineering.

[_subgenius]

Conceptually, the worst case is burning all the fossil fuels without removing significant CO2 either at the point of burning or from the atmosphere.
...
increase in temperature to +8F in 2100 to have. That's the next step.

notwithstanding your citation of only 1 study, which i assume is not qualified as "the best data", which of these 2 is actually what you assert is the "worst case inasmuch as it is supported by the best data ?"
or is there a best-data supported worst case at all?

[_Res Ipsa]

Conceptually, the worst case is burning all the fossil fuels without removing significant CO2 either at the point of burning or from the atmosphere.
...
increase in temperature to +8F in 2100 to have. That's the next step.

notwithstanding your citation of only 1 study, which i assume is not qualified as "the best data", which of these 2 is actually what you assert is the "worst case inasmuch as it is supported by the best data ?"
or is there a best-data supported worst case at all?

Sub, I gave you what I have and acknowledged it was a single study. Both are based on the same data -- they simply make different assumptions about what happens in the future.

[_subgenius]

Sub, I gave you what I have and acknowledged it was a single study. Both are based on the same data -- they simply make different assumptions about what happens in the future.

I agree, but you set a notion out in the OP about a worst case and being unable to define such a thing with any certainty certainly brings about an inevitable conclusion with regards to climate alarmism, does it not?

[_Chap]

Temperatures in the Eocene are estimated to be 9-14C higher than today, so 16-25F. https://www.ncdc.noaa.gov/global-warmin ... ene-period But this is just one paper I stumbled upon. I haven't tried to do any sort of broad search for what happens if we burn all the things. RCP 8.5 is the highest scenario that the IPCC uses, and so I think it makes sense to start there.

The next step is to look at the literature and figure out what effects we expect an increase in temperature to +8F in 2100 to have. That's the next step.

You've started a worthwhile thread. I look forward to seeing your subsequent posts.

[_Water Dog]

The "worst case" is a literally made up figure based on proven false models. It looks something like this. #ScienceSettled

float forecastTemp = ModelFuture();

if(forecastTemp > GetToday()){
writeline("WE ARE ALL GOING TO DIE");
}

float ModelFuture(){
float doomFactor = 1.5;
float todaysTemp = GetToday();
float future = doomFactor * todaysTemp;
return future;
}

[_Res Ipsa]

Sub, I gave you what I have and acknowledged it was a single study. Both are based on the same data -- they simply make different assumptions about what happens in the future.

I agree, but you set a notion out in the OP about a worst case and being unable to define such a thing with any certainty certainly brings about an inevitable conclusion with regards to climate alarmism, does it not?

No.

[_MeDotOrg]

MeDotOrg, what you just described is a positive feedback loop, not a negative feedback loop.

You're absolutely correct. Thank you for pointing it out.

[_Res Ipsa]

One of the things that is difficult to calculate for the future are the negative feedback loops that will occur as global warming continue. For example, as permafrost melts, large amounts of methane are released. Methane helps trap heat. The planet gets warmer, melting more permafrost, releasing more methane. Another negative feedback loop: as the area of the freeze line marches further towards the poles, insect populations that had been previously held back by freezing temperatures now march forward into virgin forests that have no defense mechanisms against the insects.

Personally I think every member of the House and Senate should be required to write a letter to the first American child born in the 21st Century, telling that person why you thought there was or wasn't man-made climate change, and what guided your decision making process.

Postive feedback, right? :wink

For some context: Ice cores document the relationship between CO2 and temperature over the last 800,000 years.



During this period, the primary driver of climate change was the sun -- specifically cyclical variations in the earth's orbit that caused the planet to warm and cool. CO2 acted as a feedback. The trough in the graphs correspond to ice ages. As the planet warmer, carbon that had been sequestered in the frozen ground was released to the air as CO2 and methane. Increasing CO2 added additional warming to the atmosphere. The CO2 and water vapor feedbacks led to increased temperatures far in excess of the increase caused by the solar cycles alone.

We still have large areas of permafrost in the Arctic. The temperature in the arctic increases faster than the average due to polar amplification. Melting that permafrost will release additional quantities of greenhouse gases into the atmosphere, leading to further warming. However, this positive feedback is not included in the IPCC forecasts, including the AR 5. http://iopscience.iop.org/article/10.10 ... 110B710.c1

The Global Climate Models used for the IPCC forecasts are based on equations that describe physical processes. One of those equations is the radiative forcing of the various greenhouse gases. Another is the increase in water vapor resulting from increased temperature. If there is insufficient data in the scientific literature to mathematically describe a process, that process is not included in the model. As of the cutoff date for new equations to be added to the models for the AR 5 report, the modelers' concluded there was insufficient data on which to model the permafrost thaw. So, they noted the expected feedback, but disclosed it had not been included.

I tried to find a recent literature survey on the expected greenhouse gas emissions from melting permafrost, but couldn't find one. This has been a hot area of research, and there are papers galore. Based on what I read through, the highest estimates of additional temperature change for 2100 were about .5C, with estimates running down to zero. The big question is how fast will the permafrost actually melt?

If you're trying to keep warming to 1.5C or 2C, .5 C is a pretty big deal, as it means there is a smaller budget of carbon that can be burned in order to reach those goals. In terms of the worst case scenario we're looking at, it increases from around 4C to around 4.5C