Staying within 2C part 4

Realistically it is not possible to keep within 1.5C of global warming without the use of carbon dioxide removal from our atmosphere on a massive scale. Is it realistic to keep within a 2C limit with no carbon removal technology in face of a growing world energy demand? The mathematics of this is explored.

Part 1. Overview....Realism

Part 2. Equations and assumptions used.

Part 3. Where we were at the end of 2015. 2015 progress report.

Part 4:- Progress report 2025 (hypothetical).

Out of the many possible pathways in growth, both in terms of alternatives and the total global energy consumption, I will look at two possible outcomes.

First example report for 2025.

This first example is the report that we don’t want but if we continue as we have done in the last ten years this maybe what we will get. By considering how the rate of growth of atmospheric CO2 has increased over the last 10 years (link to NOAA )

and extrapolating this forward then this would be the likely outcome.

G(e) is the total energy growth and g(a) is the growth in alternatives.

Hypothetical progress report
Year ending				2025
The indicators
				Total Ao		Wind Solar A1		Hydro Nuclear Biomass
Alternatives today (2025) /%				18.6		1.2		17.4
CO2 concentration/ppm				423
..rising at/ppm per year				2.34
Consequences                                                                                                           for staying within 2C:- (assuming a climate sensitivity of 2.8C for doubling CO2 concentrations) and ( pre-industrial concentration of CO2 at 280ppm)
1. Years left at today’s rate (2025) of emissions				15.6
2. And for the following growth pathways:-
G(e)	g(a)	year decarbonised	Pulse:- No of years of emissions at today’s rate		Overshoot factor		Possible T anomaly
%	%	year	years/factor		factor		C
2.0	4.0	2112	115		7.36		3.65
2.0	5.0	2083	59		3.79		2.81
2.0	6.0	2069	39		2.52		2.46
2.0	7.0	2060	29		1.89		2.27
2.0	10.0	2047	17		1.08		2.02
3.0	5.0	2112	180		11.60		4.46
2.0	5.0	2083	59		3.79		2.81
1.0	5.0	2068	32		2.09		2.33
0	5.0	2059	22		1.41		2.13
-1.5	5.0	2051	14		0.93		1.98
G(e)	g(a)	Ao	A1		g (lin)		T
1	26	18.6	1.2		2% of 0.174		2
2	30	18.6	1.2		2% of 0.174		2

Table 1. Possible progress report 1 for 2025.

The alternatives have increased since 2015 but at the same rate as fossil fuel consumption and therefore the percentage share has remained the same. This means that the year for decarbonising (3^rd column) for any particular growth pathway is ten years further away. This also means that the emission pulse for a given pathway (4^th column) has remained the same in terms of no of years at emission of today’s rate (2025) of emissions, but as that is greater than 2015 the emission pulse  while decarbonising for a given pathway has increased. More importantly the no of years left (15.6) at today’s emission rates to stay within 2C has decreased by more than ten years (from 2015) due to the increase in emissions and therefore the overshoot factor (column 5) is considerably bigger. This of course results in a greater temperature increase over preindustrial levels and the new pathways required are exceptionally arduous.

For a 2% increase in energy related growth we would need:-

 An annual compounding increase of 10% on our total present day (2025) alternatives that don’t contribute to emissions.

OR

If we could manage no more than 5% growth in alternatives we would require the global energy related growth to fall by 1.5% per annum.

Or

 If we relied mainly on the growth of the 1.2% of the solar/wind category then we would require an exponential growth from 2025 of 26% per annum. This rises to 30% per annum if the global energy growth is 2% per annum.

 Otherwise we are “crossing our fingers” and we hoping the climate sensitivity is smaller or we call on the technological demands imposed on our children to not only pursue  the ever increasing requirements of increasing alternatives but to do so at the same time as creating geo-engineering schemes to remove CO2 from the atmosphere.

This report above highlights mathematically the consequences of further procrastination for the next 10 years.

Second example report.

Year ending	2015
The indicators
	Total Ao	Wind Solar A1	The rest
Alternatives today /%	24	5	19
CO2 concentration/ppm	422
..rising at/ppm per year	2.3

Table 2. Possible progress report 2 for 2025.

At first sight this seems only marginally better than the above report and we could conclude the following would be necessary to stay within the limit of 2C:-

For a 2% increase in energy related growth we would need:-

 An annual compounding increase of 9% on our total present day (2025) alternatives that don’t contribute to emissions.

OR

If we could manage no more than 5% growth in alternatives we would require the global energy related growth to fall by 0.5% per annum.

However we can see that the percentage of alternatives have grown largely because of the solar/wind category and if this growth continues then we will meet out target. This represents a pathway where we have likely not followed an expansion of nuclear energy but have focussed on the renewable pathway of solar and wind. This pathway is the pathway envisaged in the 2015 report whereby we have done the minimum of expanding these renewables at 15% per annum and so a continued pathway of 15% per annum will keep as near the limit. Of course 15% increase becomes greater in absolute terms year by year however the financial incentives to decarbonise should increase if the fossil fuel market is being seen to collapse from both market signals and regulatory foresight. We have reached year 10 of the hypothetical pathway from 2015

. See fig 1 below.

Figure 1. Year 10 of a pathway from 2015.

In this scenario the fossil fuel emissions have just peaked. If we continue on this pathway CO2 emissions will fall but atmospheric concentrations will still rise for a considerable time as we move towards decarbonisation in a further 22 years time. This represents a minimum that we should be aiming for since it may keep us within 2C but is well short of the 1.5C that we should be aiming for.