Feedback-Emissions such-as-they-were all mixed up with the Budget-Emissions. So concentrations are as in the UKMO model, a function of the Contraction Budget Shapes UKMO drew - i.e. all decelerating.
Segregated-Feedback [SF] is the approach defined in CBAT where, despite the almost insuperable problems of 'empirically measuring' these, the acceleration potential of such feedback effects is included as it is this dynamic that becomes most significant.
Feedback-emissions [from all effects whatever they might be] are segregated from budget-emissions. So concentrations with CBAT segregated, are a function of the combination of [a] Budget-Emissions and [b] Feedback-Emissions-[Effects] i.e. accelerating.
Centered on Slider at '0' [CAF 50] each Slider Step above or below the adjacent Slider Step, represents a constant incremental shift of the total weight of carbon added to or subtracted from the atmosphere, over that time period.
Centered on Slider t '0' [CAF 50] each Slider Step for emissions represents over that time period, a constant incremental additon to, or subtraction from, the basic weight of the Budget [LOW, MEDIUM, HIGH] emitted to the atmosphere.
Centered on Slider at '0' [CAF 50] each Slider Step above or below the adjacent Slider Step, an increment of a gradually accelerating weight of carbon added to or subtracted from the atmosphere, over that time period.
Centered on Slider at '0' [CAF 50] each Slider Step for emissions represents an increment of a gradually accelerating weight of carbon emitted to, or subtracted from, the basic weight of the Budget [LOW, MEDIUM, HIGH] emitted to the atmosphere, over that time period.
CONCENTRATIONS - Different for INTEGRATED [Convex - Decelerating] & SEGREGATED [Concave Accelerating].
However, the different 'Budget-Paths-Integral' over the years 2010 to 2110 for Concentrations with: -
'Integrated Feedback' is 'convex', i.e. while it is rising, the rise is slowing over time and falling if the 'Fraction of the Emissions Budget Returned to sinks' becomes greater that 100% of the Emissions Budget in any given year.
This is the UKMO's method as in the UK Climate Act 'Median Case'. This is the result of omitting significant feedback effects and CBAT reasonably models this with slider-positions below '0'.
'Segregated Feedback' is 'concave', i.e. while it is rising, the rise is accelerating over time if the 'Fraction of the Emissions Budget Returned to sinks' remains greater that 50% of the Emissions Budget in any given year. This is the CBAT method of correcting these feedback omissions in the the UK Climate Act and CBAT reasonably models this with slider-positions above '0'.
Whatever the size of the BUDGET chosen [HIGH MEDIUM LOW] and the type of feedback chosen ['Integrated' or 'Segregated'] this Slider-Position structure remains proportionate in the way described above.
These Segregated Feedback curves should be understood as deliberately including both potential direct CO2 emissions-releases and also converting non-CO2 feedback-emission-releases [e.g. CH4] and also related feedback effects [e.g. Albedo-Loss, Negative Albedo-Gain] converted to CO2-Equivalence, all with 'layered-trend-regularity' over time.
This means that going over 'tipping-points', is not so much 'abrupt' as gradual, imperceptible but increasingly irrevocable progressions over future-time.
Understood like this, the essential property of CBAT SF curves is revealed as showing the rising-risk-potential for the loss of control due to feedback-acceleration - specifically over and above the UKMO's purely 'deceleration-construct' of CO2-budget-emissions - as the planet warms over time.
The CBAT default is set toIntegrated-Feedback which simulates the UKMO's 'climate-control-model', as in the UK Climate Act. In this, feedback-emissions are unspecified, mixed up with and indistinguishable from budget-emissions, in deceleration patterns for emissions and concentrations.
This is only explicable if significant feedback-effects, omitted from the model and a picture of the future is that the planet will be cooling and concentrations are going to be significantly to less than CAF 50.
" . . . other Earth system feedbacks, associated for example with the cycling of carbon through natural systems andreleases of carbon from permafrost melt, will change, and are likely to increase the actual expected warming."
The point is that these feedback-releases are still not included in the climate-models underpinning IPCC AR5 [see UNEP Report] or in the UKMO model used to generate the UK Climate Act.
In other words, the 'Segregated Feedback Model' is the less unrealistic than the 'Integrated Feedback' modal as it lays out a credible range for the potential 'feedback footprint' associated with warming, that is just screened-out in the UKMO's 'Integrated Feedback Model'.
A recent helpful, wider discussion of this 'measurement-dilemma' by Nafeez Ahmed is here
In a nutshell, this is a risk-judgement comparing 'control curves' versus 'loss of control curves'.
Making this judgement recognizes that pursuing growth of the economy by running risks that we don't have to run, will end up creating feedbacks with costs that we cannot afford to pay.
In the 'live-imagery' below, the CBAT GUI is set to the default of Integrated Feedback in the UKCA. Switch on the UKCA and move the slider to equal the 'Upper Airborne Fraction' in the UKCA [516 PPMV].
Here again is the CBAT GUI 'live'. Change the Integrated default to Segregated, switch on the UKCA and again, move the slider to equal the 'Upper Airborne Fraction' in the UKCA [516 PPMV].
When the slider in both is set concentrations in 2110 [i.e. at the upper band [90%-ile] of the UKCA], it is very easy to compare the difference in effect
between Integrated and Segregated Feedback effect with UKCA.
This is the generic and visible difference of deceleration and acceleration curves. It is the difference between Integrated-Feedback-Curves [as from UKMO and in the UK Climate Act] which are convex [deceleration] and the Segregated-Feedback-Curves [as essayed in CBAT] which are concave [acceleration].
In fact it is worth zooming on this to see in detail the difference, in the shape and weight in concentrations over the first 100 years, between UKCA [90%-ile] & CBAT. This UKCA 'Integrated Feedback' curve [90%-ile] has been modelled to arrive at 516 PPMV in 2110 and the CBAT 'Segregated Feedback' curve has been selected to match that value in 2110.
Throughout the Century [2010-2110] the CBAT 'slow acceleration curve' is significantly below the UKCA 90%-ile 'slow deceleration curve'. The key point to note is that even if a lower CBAT curve of segregated feedback effects were selected [so concentrations intersected the UKMO line only in 2140 for example], once this feedback has been triggered by the warming, there is very little we can do to stop or even mitigate that.
The policy-implication for UNFCCC-compliance is to choose 'LOW' - a smaller emissions-budget - with a view to triggering less feedback.
If we choose a larger emissions-budget [as with the UK Climate Act for example] we may well trigger uncontrollable rates of feedback-emissions that will accelerate, outpace and even overwhelm efforts at UKCA rates of global budget-emissions control.
Extensive evidence from GCI was presented to the 2nd UK House of Commons Environmental Audit Committee Enquiry into this matter in June 2013.
In this, GCI compared the upper band of the UKMO model 'integrated-feedback-effect' on emissions-concentrations to 516 PPMV by 2110 [as in the UKCA], with the CBAT 'segregated-feedback-effect' on emissions-concentrations to the same 516 PPMV by 2110.
The significant difference is immediately apparent.
The UKMO model is unrealistic. Next to that CBAT is much less unrealistic.
The UKMO model is unrealistic as it shows feedback-emissions jumping up very suddenly between 2010 and 2016 and then remaining roughly constantly stable at an ouput value of around 2 Gt C a year for the next Century with concentrations rising sharply at the outset and then just slowing down over the next Century. They project this whilst also projecting that the planet warms to ~ 3 degrees Celsius above pre-Industrial temperature by 2110. In this model, feedback-emissions from permafrost melt for example are simply left out.
The CBAT model next to that is realistic as it shows feedback-emission rising slowly from 2010 and just accelerating at a constant rate increasing the output value per annum [the user can select the rate] with concentrations rising slowly as a 50% function of that rate of feedback-emissions over the Century ahead.
What comes clearly into view when those two methods are compared [both arriving at 516 PPMV in 2110 as shown in this example] is that UKMO's unrealistic approach is alarmist whilst also being misleading. The UKMO curves for concentrations are consistently higher that the CBAT curves for the 100 year time-frame and the UKMO curves for emissions are consistently higher for the first 50 years.
However, UKMO's approach is also seriously misleading, as it falsely suggests that 'we will be keeping 'control' over the Century ahead by simply enacting the budget-emissions control as in defined in the UK Climate Act [2016 4% low].
The greater likelihood is that we won't be keeping so much as losing control, with this CBAT MEDIUM Emissions Budget i.e. acheiving zero emissions globally by 2110, as feedback emissions-concentrations will accelerate uncontrollably as the planet warms and the permafrost melts.
As this happens it makes it increasing probable that 'we will actually be losing control' of the rates of climate change. If so, this is a recipe for doing too-little too-late and then cooking the planet as we absurdly act it out.
If we are to have any chance of 'keeping control', the Emissions-Budget will need to be nearer the CBAT 'LOW' Emissions Budget, i.e. reflecting the emergency we are in and achieving zero emissions globally by no later than 2050, led and accompanied by vigorous transition policies and measures.