The planet is warming – and the imperative to transition to cleaner, greener energy sources has never been clearer. With the help of an environmental engineer, create maps out possible futures for global emissions, and how fuel and electricity demand could soon outstrip supply.
The chart below would be familiar to anyone who’s paid attention to the climate discussion, especially after the Paris Agreement was signed in 2016.
The data is drawn from the Global Renewable Energy and Sectoral Electrification (GREaSE) model published by Hopeward et al. (2025), based on projections of population growth, industrial activity and climate policy positions.
The graph presents how cumulative global emissions of carbon from burning fossil fuels, in gigatons, could change over the rest of this century, depending on the strength of the world’s action on emissions reduction.
The area shaded light orange is RCP 1.9, a pathway which would hopefully limit an increase in the global temperature to below 1.5°C – the aspirational goal set by the Paris Agreement. It implies minimal future global emissions, meaning stringent action on climate, including the elimination of fossil fuels in favour of renewables and increased electrification.
A weak climate policy combined with medium population growth and continued industrial activity – meaning zero electrification of industry and a continued reliance on fossil fuels – pushes us into the territory of RCP 4.5.
RCP 4.5 is an intermediate scenario which would trigger sea levels to rise 35 per cent higher than the preceding pathway, RCP 2.6, and the global temperature to rise by up to 3°C by 2100.
No policy at all could leave us reaching into the territory of RCP 6.0, and potentially grappling with cumulative fossil fuel emissions close to 700 GtC by the end of the century.
It goes without saying that this pathway would leave the planet significantly hotter, with substantial impacts on the environment and quality of life.
By contrast, full electrification of industry – even with a high increase in population and an increase in industrial activity – could see emissions drop back almost into the territory of RCP 2.6; more manageable, but still not ideal.
Shifting the lever
Now, let’s examine how changing supply of fuel and electricity intersects with demand across different energy sources.
Spoiler alert: there’s often a mismatch between the two.
Let’s assume medium population growth, future economic activity commensurate with current activity – so, no significant uptick or reduction in economic activity – and a weak climate policy.
In an extreme – but not impossible – scenario where fossil fuels still reign and no electrification takes place, demand for both fuel and electricity quickly rises above supply.
When breaking down demand for energy by sector – coal, gas, renewables, and so on – we can see that, in this hypothetical scenario, even an increased reliance on coal by the middle of the century won’t help us meet that demand.
Now, let’s consider the impact of electrification.
Heavy electrification efforts done very quickly would have an extremely strong impact when it comes to reducing emissions – which is, of course, inherently a good thing.
But notice that critical gap between supply and demand. Renewable energy networks take time to build. By electrifying quickly and also phasing out fossil fuels quickly, we introduce the risk of energy scarcity – even if projections indicate our being able to meet aspirational energy demands by mid-century, for instance, as presented in this graph.
Communicating this danger is a key focus for James Hopeward, Associate Professor in Environmental Engineering at the University of South Australia.
“As we roll out renewable electricity, we need to build all the turbines, solar panels and so on,” he told create. “The faster we build them, the more energy is drawn out of the system, and the more it reduces the electricity supply.
“In other words, the faster we try to divert our energy into building renewable electricity, the more we might inadvertently reduce our net supply and temporarily induce further scarcity.”
This issue becomes even more pressing when combined with aggressive climate policy.
Very strong action on climate – phasing out coal and gas in favour of renewables – exacerbates this rift, and continually rising demand could significantly outstrip supply.
“The stronger the climate policy, the more it shifts the lever away from fossil fuels and towards renewables,” Hopeward said.
Conversation starter
Hopeward isn’t looking to scare engineers and leaders off from implementing renewable energy solutions. Rather, he intends to spread awareness of how important forward-thinking policy approaches are.
A new open-source tool called GREaSE (Global Renewable Energy and Sectoral Electrification) has been designed to promote understanding of the complex relationships between components of the energy system.
The interactive model can rapidly generate transition scenarios that highlight the twin risks of energy scarcity and emissions overshoot.
“Engineers are the sort of people who typically are on board with the need for an energy transition,” Hopeward said, adding that he is particularly interested in encouraging awareness of how different factors influencing that transition intersect.
“It’s important we understand that, if we’re to have a growing population and aspire to continue driving cars around and fly planes, those things will influence our energy demand, which in turn influences our fuel and electricity demands.”
The tool is precisely that: a tool designed to foster discussions. And the data presented in this story – data you can also experiment with – is hypothetical and based on certain assumptions. This is deliberate.
“The really sophisticated integrated assessment models do way more sophisticated things than this model does. But the more complicated a model, the more time it takes to wrap your head around it and communicate the ideas to others.
“I feel like that creates a gulf between where the science is and where the public discourse is. I wanted to address that gulf with this tool.”
The data in this story is drawn from the Global Renewable Energy and Sectoral Electrification (GREaSE) model published by Hopeward et al. (2025). You can read the full paper, download the mathematical model and use the interactive tool.
Catch James Hopeward at the Engineers Australia Climate Smart Engineering (CSE) 2025 conference in Adelaide in August, where he will present a new analysis using the GREaSE tool applied to the energy transition in Australia.
Alarmist. Disappointing. This takes for granted computer modelling that makes heroic assumptions and continues to overstate potential changes and their impacts. Why is a journalist needed for EA communications? EA should be focussing on solutions and avoid being part of the problem. Why isn’t it supporting removal of barriers to nuclear energy for a start?
Hi Ken,
Your comment is appreciated. Nuclear energy was included in the original modelling (and appears in the plots in the article above). The paper is open access (link below), so you can check out the data that went into it. The numerical model is deliberately simple and designed to be accessible (Excel based) so anyone can download it and play with it. There’s a link to the GitHub model within the paper.
https://www.mdpi.com/1996-1073/18/9/2205
Another disappointing piece that does not represent the range of views held by our engineering membership or the engineering profession. Projecting certainty where it does not exist is not who we are. We need to acknowledge that our profession has a range of views, and that prudence while we continue to analyse and learn is not sacrilege. Faster & faster investment in renewables may not be the best path and I have never seen more highly competent power system people more deeply concerned for the trajectory our electrical network.
His passion is “accurate use of apostrophes”. I like that too, but I am not quite passionate about it!