One of the charts, in particular, shows how global heating will increasingly severely impact people the later they were born. For example, I was born in 1968 (323ppm CO2), so if I live to 85 or so, then that will be just into the zero-carbon era, if the world can achieve the intention of the Paris Agreement, but that zero-carbon era will almost certainly be over 1.5ºC warmer than pre-industrial times.
There is increasing controversy over the way in which IPCC report policy statements have been watered-down in order to please politicians and the fossil fuel industry. Kevin Anderson covers this well in an article in The Conversation. In a sense, although we're just at the point where renewable energy deployment has reduced the rate of increase of CO2 emissions to near 0 (300MT in 2022 vs 1.4GT in 2021 [Refs]) we are also heading in the wrong direction; for example COP27 being hosted by a fossil fuel industry CEO; or new UK coal mines shortly after hosting COP26.
In addition I've been watching TickZero's YouTube videos explaining why there's little chance that we can meet net-zero by 2050 - the modelling here uses deployment latency to conclude we have to reduce energy usage by about 60% between now and 2050 in order to avoid the 50% chance of overshooting 1.5ºC. @KevinClimate's recent SGR article also makes the point forcefully:
“But such a rapid deployment of existing zero carbon technologies, in itself, can no longer be sufficient. We’ve left it so late that technology will never deliver in isolation”
People have interpreted this to mean steep reductions in energy demand, but currently I'm struggling to find the relevant Kevin Anderson quote for this:
“As always @KevinClimate sees through the smoke and mirrors! We cannot achieve deep mitigation without steep reductions in demand.” https://twitter.com/kristiansn89
As someone outside of academic circles, I'm not aware of the datasets and appropriate models needed to accurately determine what kinds of mitigation is needed, but I am interested in exploring simple models that can provide rough (but reasonable) answers to questions about the depth of mitigation and demand reduction.
The Model
My approach is fairly simple, let's assume we start with the current global energy budget. Some (most) is provided by fossil fuels and some (mostly electricity) is provided by renewable energy. Some is provided by Nuclear energy (which I don't think I've included in my model, though I can update it fairly easily to do that). If we want to fully decarbonise between now and 2050 using renewable energy (which is far easier than using nuclear power or carbon capture), then we have to allocate some of our energy budget each year to building renewable technology. The amount we allocate, directly translates into the amount of renewable energy we generate; how quickly it's deployed and how much additional energy it provides.
Global Energy
So, first we need to know how much energy we used in 2022. Now, you may find it fairly surprising, but a simple Google search for "Global energy used 2022" doesn't give you a straight answer: a figure in TWh. However, what I did find was the amount of electrical energy produced (27TWh [1]) and the proportion of global energy that's electric (20.4% in 2021 [2], which I interpreted to mean could reach 21% in 2022). So, this gives: 129TWh for global energy. I also found out that about 11% is solar heating [3].
Secondly, we need to know how much electricity is produced using renewable energy, it's currently about 29% [4], so we know that 27TWh*0.29 = 7.83TWh is renewable sources (e.g. wind, solar, hydro).
Renewable Investments
We know that Wind Turbines produce a return on investment, given their manufacturing costs, of about 21:1 (over twice as much as for fossil fuels), and if we assume that a Wind Turbine lasts 25 years, then that means 1kWh invested in a Wind Turbine produces 21kWh of energy over 25 years, which is: 0.84kWh per year. I assume the same is true for Solar PV and that there's an even mix of both [5]. Finally I know that Wind and Solar energy is getting cheaper every year, and I assume it's getting better by 7% per year, which translates into a ROI increase of 7% every year [6][7]. It's actually been twice as good as that ([6] says the improvement is $5.66/W to $0.27/W => 16% per year and [7] directly says 16%/year) and that the 21:1 ratio is from the early 2010s, and so it's significantly better now. I am assuming diminishing improvements.
So, just based on this information we can generate a model for how much energy we need to invest per year just to reach 100% renewable energy (not electricity) by 2050. That's the first value you can control in the model.
Energy Reductions
The TickZero videos and Kristiann89's tweet argue that we need to reduce energy usage as well over this period. We can combine the previous model with energy reductions by simply taking the total energy reduction we expect in total and applying the (2050-2022) = 28th root of it. For example a 60% reduction means we're left with 40% of the energy so the energy reduction is 28√0.4 = 0.968, so each year we have 96.8% of the energy of the year before, a fall of 3.2% per year.
Energy reductions for people are like applying austerity. If we have to use 3.2% less each year, and we can't gain 3.2% more efficiency (certain), then that means we will have to ration energy usage. The combined amount of energy reduction for people will be the renewable investment + the energy reductions. If TickZero and Kristiann89 are correct and this model would be approximately correct, then that's 3.2+1.52 = 4.82% energy reductions per year, roughly a Covid-19 pandemic impact every year between now and 2050.
CO2
The primary limitation on energy and renewables is the carbon budget. The remaining carbon budget as of 2023 is taken to be 455000 MTonnes of CO2 (or maybe CO2e, which this model doesn't consider). to have a 50% chance of staying under 1.5ºC. For a 50% change of staying under 2.0ºC the carbon budget is taken to be 1375000 MTonnes of CO2. It's possible I'm quoting for the budgets that allow the temperature of overshoot providing that global temperatures return to 1.5ºC or 2.0ºC respectively, but this isn't crucial to the model, since the budgets can be adjusted.
We can calculate how much emissions we expect based on the the global energy usage and the amount of fossil fuels (TotalEnergy-Renewables-ZeroCarbonHeating) by knowing the CO2 produced by burning fossil fuels. This depends upon the kind of fossil fuels in general. We consider the primary components: Coal (at 0.85kg of CO2e per kWh[9]) and gas (at 0.49kg of CO2e per kWh[9]) and so the overall emissions are governed by the mix, which in this model is just a constant (by default 1:1 Coal:Gas [10]).
Simulations
It's possible to write a crude simulation involving these few variables: Total Energy, Energy Reductions over time, Renewables Investment and a mix of fossil fuels that lead to CO2 emissions. The simulation provides a default set of values and you can tweak them to see what happens under various conditions. Most of the information is shown with simple curves covering the years 2022 to 2050. When CO2 emissions exceed the 1.5ºC budget the background is banded in light yellow which increases linearly to pink as emissions reach 2.0ºC. It's not an accurate scale, mid-way between yellow and pink doesn't necessarily mean 1.75ºC is likely to have been breached. Instead it's an indication of severity of emissions.
Results
The default simulation hits +1.5ºC sometime in the late 2020s and gets to +1.8ºC by 2050. This is roughly similar to actual climate models in the sense that it involves major global investments and when it hits +1.5ºC. It involves a decline of 3.2% of energy usage per year.
It's possible to alter the parameters so that the overall energy loss to humanity is reduced - and correspondingly the renewables investment must be higher. For example if we don't reduce energy usage over time; and want to hit the same maximum temperature of +1.8ºC, then we need to invest 3.55% of global energy every year, and we hit zero carbon by 2043.
It's possible to explore trade-offs that result in zero-carbon before 2050 (and for developed countries there's a strong argument to say it should), but scenarios that avoid 1.5ºC altogether require investments + losses that exceed 10% per year. Again, this concurs with IPCC and other climate science models which emphasise the difficulty of achieving this: i.e. the virtual impossibility given the current lack of political will. As Kevin Anderson has said:
“There are no non-radical futures.” https://twitter.com/70sBachchan/status/1415023625183404036?s=20
Conclusions
I came into this model accepting the premise that we need steep declines in energy usage in order to reach zero-carbon. The model that agrees with TickZero's energy decline involves a 1.52% global energy investment per year, but in effect this has a 4.7% impact on energy per year at a personal level, something close to the crash of 2008 or the Covid pandemic.
I am not sure that society could deal with that kind of stress year on year for the next 27 years. Even then, the temperature rise is +1.8ºC, significantly higher than Paris and we hit it this decade.
The model also shows that for a constant energy usage, remaining at today's energy usage, and limiting the temperature rise to +1.8ºC, we would need a 3.55% global energy investment per year, which is a 3.55% hit for the first year followed by a 0% impact on energy per year at a personal level and we get to zero carbon about 7 years earlier.
It's certainly possible for society to take that kind of hit for a single year. To my mind, this is an easier and better course of action.
Why does it work that way? The simple answer is that a decline in energy usage leaves fewer resources available to invest in renewable energy. The argument for energy decline is that it will be impossible to ramp up renewable energy quickly enough, but ironically this model implies that it will actually make decarbonisation harder to achieve. In other words, reductionism is a far less feasible solution.
You are free to take this model and improve it, since it is undoubtably crude. The source code can be read easily by simply viewing the html for the page. Please bear in mind that the objective is to provide a simple model that can be readily understood. Essentially this model achieves that by treating the carbon budget as a proxy for complex climate equations.
Refs
[1] and
[4] https://www.weforum.org/agenda/2023/03/electricity-generation-renewables-power-iea/ Search for "29% to 35%" Nuclear growth 3.6%/ year.
[9] https://www.parliament.uk/globalassets/documents/post/postpn_383-carbon-footprint-electricity-generation.pdf Page 2.
Possible Corrections
https://www.carbonbrief.org/guest-post-what-the-tiny-remaining-1-5c-carbon-budget-means-for-climate-policy/ says that the Carbon budget for 1.5ºC in 2020 was about 500GTCO2 and that we generated 70-80GtCO2 in 2020-2021 => 37.5GTCO2 per year average, with 40GTCO2 in 2022. So, that's about twice my estimate, because I have 71GTCO2 for 2022. This leaves a remaining budget of 380GtCO2 from the start of 2023, about 70GT lower than mine. Or it could be as low as 260GT.
https://www.carbonbrief.org/analysis-what-the-new-ipcc-report-says-about-when-world-may-pass-1-5c-and-2c/ 460bn tonnes of CO2
Further Reading
Decarbonisation Sim
Renewables Investment %:Renewables Improvement%:
Energy Decline%:
Coal/GasRatio%:
