Fair Plan 10 : Post-Trump Global-Warming Mitigation

With the election of Donald Trump as President of the United States of America, it appears likely that the initiation of mitigation of human-caused Global-Warming/Climate-Change will be delayed many years. Accordingly, here we calculate the Emission Phaseout Duration, D = YE − YS, where YS and YE are the Start and End Years of the emissions reduction, for YS = 2020, 2025 and 2030, and maximum Global Warming targets, ∆Tmax = 2.0 ̊C, 1.9 ̊C, 1.8 ̊C, 1.7 ̊C, 1.6 ̊C and 1.5 ̊C. The 2.0 ̊C and 1.5 ̊C maxima are the “Hard” and “Aspirational” targets of the 2015 Paris Climate Agreement. We find that D decreases with increasing YS from 2020, and with decreasing ∆Tmax. In particular, D decreases from: 1) 76 years for YS = 2020 to 53 years for YS = 2030 for ∆Tmax = 2.0 ̊C, and 2) 34 years for YS = 2020 to 7 years for YS = 2030 for ∆Tmax = 1.5 ̊C. Thus, delaying the initiation of the phaseout of greenhouse-gas emissions from 2020 to 2030 makes it more difficult to achieve ∆Tmax = 2.0 ̊C and impossible to achieve ∆Tmax = 1.5 ̊C.


Introduction
On 28 March 2017, the Trump Administration declared war on: 1) Climate Science, 2) Climate Scientists, 3) the Obama Administration's program to mitigate Human-Caused Global Warming/Climate Change = the Clean Power Plan, and 4) humanity's preventing further Human-Caused Global Warming/Climate Change [1].
On 1 June 2017, the Trump Administration performed a likely coup de gras to the 2015 Paris Climate Agreement by signaled its intention to withdraw therefrom [2].
In the course of human events, these declarations of war are faux pas of the gravest magnitude.
Herein we explicate why this is so, and we chart a future, post-Trump course of greenhouse-gas emissions reduction to reverse it.
Herein we shall answer the question: How many years before 2100 do we need to zero the emission of greenhouse gases for every year post 2020 we delay initiating the reduction of greenhousegas emissions in order to keep global warming below: 1) the 2˚C maximum Global Warming adopted by the UN Framework Convention on Climate Change (UNFCCC) in 2010 at the Conference of the Parties 16 (COP16) in Cancun, Mexico, "to prevent dangerous anthropogenic interference with the climate system" of [3] = the "hard" target of the 2015 Paris Climate Agreement [4], and 2) the 1.5˚C maximum warming adopted by the UN Framework Convention on Climate Change (UNFCCC) in 2015 at the Conference of the Parties 21 (COP21) in Paris, France, = the "aspirational" target of the 2015 Paris Climate Agreement [4]?

Reference Emission Scenario
As our Reference emission scenario, we take the RCP-8.5 emission scenario [5] developed by the International Institute for Applied Systems Analysis (IIASA) in Laxenburg, Austria, as one of the four emission scenarios for the fifth assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) [6].RCP-8.5 is the highest of these four emission scenarios and leads to a radiative forcing (the change in the net incoming radiation at the top of the atmosphere) of about 8.5 Wm −2 in 2100.For comparison, a doubling of the preindustrial carbon dioxide (CO 2 ) concentration causes a radiative forcing of 3.7 Wm −2 .RCP-8.5 is the way the world would likely emit greenhouse gases if either there were no consequent climate change or if we were completely ignorant of the climate change.
The CO 2 emission rate for the Reference scenario is shown in Figure 1 for the 21 st century alone, the time period of interest herein.The CO 2 emission rate rises from about 29 billion tonnes of carbon dioxide per year (Gt CO 2 /year) in 2000 to Figure 1.Annual CO 2 emission rate [Gigatonnes of CO 2 per year (GtCO 2 /year)] versus year in the 21 st century for the Reference (RCP-8.5)scenario.

Reduced-Emission Scenarios
We define our reduced-emission scenarios for each of the above species by ; , is emission intensity in year y for Start Year, Y S , and End Year, Y E .
It should be noted that these linear-in-time emission intensities are applied to the global emissions, not just to the emissions of the Developed Countries, as in our 10 antecedent Fair Plan papers [7]- [16].In those papers, the emission intensities for the Developing Countries were larger in the beginning years, and smaller in the later years than the linear intensities, this so that: 2) the maximum global-mean near-surface air temperature was kept below the 2˚C limit adopted by the UN Framework Convention on Climate Change "to prevent dangerous anthropogenic interference with the climate system" [3].For Y E = 2090 and 2100, the initial annual CO 2 emission rates are respectively flat and slightly increasing before they too decrease to zero in Y E .

Species Concentrations and Total Radiative Forcing
We have used the model of the Center for International Climate and Environmental Research-Oslo (CICERO) [17] to calculate the species concentrations from their emissions.
It should be noted that the CICERO model does not include the positive ocean-CO 2 -solubility/temperature feedback whereby the fraction of emitted CO 2 removed from the atmosphere by the ocean decreases with increasing temperature.Thus, ceteris paribus, our calculated CO 2 concentrations are underestimates

Global Warming
As we have in our 10 antecedent Fair Plan papers [7]

Analysis of the Global Warming Results
From the results of Figure 6 we determine the End Years Y E for each Start Year Y S = 2020, 2025 and 2030 required to keep Global Warming less than ∆T max = 2.0˚C, 1.9˚C, 1.8˚C, 1.7˚C, 1.6˚C and 1.5˚C.
Figure 7 shows the maximum temperature ∆T max for each of the curves in Figure 6 versus End Year Y E for Start Years Y S = 2020, 2025 and 2030.We fit each of the three curves in Figure 7 with a quadratic polynomial, with coefficients A, B and C presented in Table 1, together with the corresponding coefficients of determination, R 2 .

Dependence of Emissions Phaseout Duration D on ∆Tmax
We solved Equation (3) for Y E for ∆T max = 2.0˚C, 1.9˚C, 1.8˚C, 1.7˚C, 1.6˚C and 1.5˚C for Start Years Y S = 2020, 2025 and 2030.The results are shown in Figure 8.
We fit each of the three curves therein with a quadratic polynomial, with coefficients A, B and C presented in Table 2, together with the corresponding  Table 2. Coefficients of the quadratic fit of End Year, coefficients of determination, R 2 .
We then calculated the duration of the phaseout of emissions as for ∆T max = 2.0˚C, 1.9˚C, 1.8˚C, 1.7˚C, 1.6˚C and 1.5°C for Start Years Y S = 2020, 2025 and 2030.The results are shown in Figure 9.We fit each of the three curves therein with a quadratic polynomial, with coefficients A, B and C presented in Table 3, together with the corresponding coefficients of determination, R 2 .The Emissions Phaseout Period D decreases with decreasing ∆T max , but more rapidly than linearly, this because the curvature A is negative, and increases in magnitude with increasing Start Year, Y S .This means that D decreases with decreasing ∆T max more the later the Start Year, Y S .In particular, for Y S = 2020, D decreases from 76 years for ∆T max = 2.0˚C to 34 years for ∆T max = 1.5˚C, while for Y S = 2030, D decreases from 53 years for ∆T max = 2.0˚C to 7 years for ∆T max = 1.5˚C.This leads to: Finding 1: It will be increasingly difficult to phaseout emissions the smaller the temperature target, ∆T max , and this difficulty will increase the longer humanity delays the initiation of emissions reductions.because the slope A = ∆D/∆Y S is negative, and more so the larger ∆T max is.This is shown in Figure 12 which presents A = ∆D/∆Y S as a function of the allowed maximum Global Warming relative to 1750, ∆T max .This leads to:

Dependence of Emissions Phaseout Duration D on Start Year YS
Finding 2: It will be increasingly difficult to phaseout emissions the longer humanity delays the initiation of emissions reductions, and this difficulty will increase the smaller the temperature target, ∆T max .
Findings 1 and 2 are visually displayed and summarized in Figure 13

Conclusion
In  Bottom Line: In order to maximize the likelihood of humanity's achieving ∆T max = 2.0˚C, the initiation of the phaseout of humanity's emission of greenhouse gases should not be delayed past 2020.

1 )
the total cumulative traded-adjusted CO 2 emissions of the Developing Countries equaled the total trade-adjusted CO 2 emissions of the Developed Countries-the first Fairness, where trade-adjusted emissions are the CO 2 emissions generated by the Developing Countries in the production of goods and services for the Developed Countries, which emissions are debited to the Developed Countries, not the Developing Countries-the second Fairness; and

Figure 4
Figure 4 presents the CO 2 concentrations versus year in the 21 st century for the Reference scenario and for the Reduced-emissions scenarios, the latter for Start Years Y S = 2020, 2025 and 2030, and End Years Y E = 2100, 2090, 2080, 2070, 2060, 2050, 2040, 2030 (2032 for Y S = 2030).The CO 2 concentration for the Reference scenario monotonically increases across the 21 st century, from 372 ppmv in 2000 to 903 ppmv in 2100, exceeding twice the pre-industrial concentration of 278 ppmv in 2053.The CO 2 concentrations for the Reduced-emissions scenarios peak within the 21 st century, with the peak occurring later and being larger the later the Start Year, Y S , and for each Y S , occurring sooner and being smaller the earlier the End Year, Y E .The peak CO 2 concentrations exceed twice the pre-industrial CO 2 concentration for all Y S , for both Y E = 2100 and 2090 for Y S = 2030, but only for Y E = 2100 for Y S = 2020 and 2025.

Figure 5
Figure 5 presents the total radiative forcing relative to 1750 [Watts per square meter (Wm −2 )] versus year in the 21 st century for the Reference scenario and for the Reduced-emissions scenarios, the latter for Start Years Y S = 2020, 2025 and
[8] [9] [10][11] [13][14] [15][16], we have used our engineering-type simple climate model[18] to calculate the change in global-mean near-surface air temperature relative to 1750, now for the total radiative forcing shown in Figure5.In our 10 earlier Fair Plan papers, we performed calculations of Global Warming for the equilibrium climate sensitivity (∆T 2x , the change in global-mean near-surface air temperature from 1750 due to the radiative forcing caused by an instantaneous doubling of the preindustrial CO 2 concentration) estimated by us from the four observed temperature datasets in our 2012 Causes paper[19] (1.45˚C, 1.61˚C, 1.99˚C and 2.01˚C), and then averaged them.Here, we performed calculations of Global Warming for ∆T 2x = 2.0˚C.

Figure 6 .
Figure 6.Change in global-mean near-surface air temperature relative to 1750 [degrees Celsius (˚C)] versus year in the 21 st century for Start Years Y S = 2020, 2025 and 2030, and End Years Y E = 2100, 2090, 2080, 2070, 2060, 2050, 2040, 2030 (2032 for Y S = 2030).The 2.0˚C Hard Limit and 1.5˚C Aspirational Limit of the 2015 Paris Climate Agreement are shown by the brown dashed lines.

Figure 7 .
Figure 7. Maximum change in global-mean near-surface air temperature ∆T max relative to 1750 [in degrees Celsius (˚C)] versus End Year Y E for Start Years Y S = 2020, 2025 and 2030.The quadratic curve fits are shown by the dashed lines.

Table 1 .Figure 8 .
Figure 8. End Year Y E versus ∆T max for Start Years Y S = 2020, 2025 and 2030.The quadratic curve fits are shown by the dashed lines.

8
∆T max in Equation (4) for Start Years Y S = 2020, 2025 and 2030 from Figure

Figure 9 .
Figure 9. Emissions phaseout duration D versus ∆T max for Start Years Y S = 2020, 2025 and 2030.The quadratic curve fits are shown by the dashed lines.

Figure 10 presentsFigure 10 .
Figure 10 presents the End Year, Y E , versus Start Year, Y S , for maximum globalmean near-surface air temperature relative to 1750 of ∆T max = 2.0˚C, 1.9˚C, 1.8˚C, 1.7˚C, 1.6˚C and 1.5˚C.We fit each of the three curves therein with a quadratic polynomial,

Figure 11 .
Figure 11.Emissions phaseout duration D versus Start Year, Y S , for ∆T max = 2.0˚C, 1.9˚C, 1.8˚C.1.7˚C, 1.6˚C and 1.5˚C.The linear fits are shown by the dashed lines.

Figure 12 .
Figure 12.Change in Emissions Phaseout Duration per change in the Start Year from 2020, ∆D/∆Y S , as a function of the allowed maximum Global Warming relative to 1750, ∆T max .

Figure 13 .
Figure 13.End year, Y E , required to keep Global Warming below ∆T max = 2.0˚C and 1.5˚C relative to 1750 for Start Years Y s = 2020, 2025 and 2030.

Table 5 ,
together with the corresponding coefficients of determination, R2.The emissions phaseout duration D decreases with increasing Start Year, Y S ,

Table 4 .
Coefficients of the quadratic fit of End Year on Start Year,

Table 5 .
Coefficients of the linear fit of Emissions Phaseout Duration on Start Year, which presents the dependences of End Year, Y E , and Emissions Phaseout Duration, D, on temperature target, for ∆T max = 2.0˚C and 1.5˚C, and on Start Year, for Y S = 2020, 2025 and 2030.It is clearly seen that Y E and D decrease with increasing Start Year, Y S , and decreasing Global Warming target, ∆T max .