Energy transitions and climate

By the end you will be able to

• Distinguish the fuel, prime mover, electrification and efficiency layers of an energy transition, and explain how accounting methods change reported shares
• Describe how long coal, oil and gas took to spread and why national transitions differed in speed
• Explain why scale, asset lifetimes, lock-in and rising demand slow the shift away from fossil fuels
• Separate relative from absolute decarbonisation and identify why ammonia, steel, cement and plastics are hard to abate
• Summarise the evidence on CO2 and warming, the remaining carbon budget, and the IEA's 2025 scenarios

Contents

1. Part 1 What a transition is and how fast transitions run

   Talk of 'the energy transition' suggests a single switch from one kind of energy to another. History shows something messier: several overlapping changes in fuels, machines and uses, each unfolding over decades. Before judging today's shift away from fossil fuels, it helps to know how earlier shifts were measured, how long they took, and why countries moved at such different speeds.

   • A transition changes fuels, machines and uses, and the way you count it matters
   • Each new fuel needed decades to win a quarter of world supply
   • Old fuels lose share but rarely lose volume
   • Countries moved at very different speeds, set by resources, size and policy
2. Part 2 Why transitions are slow

   If solar power now gives the cheapest new electricity in much of the world, why do fossil fuels still supply most energy? The answer lies in the sheer size of the system, the long lives of its machines, the way fuels, converters and networks are bolted together, and the stubborn fact that demand keeps rising. Each of these slows change, however cheap the new technology.

   • The fossil system is the largest machine humanity has built
   • Long-lived assets and locked-in networks resist early retirement
   • Rising demand absorbs much of the new clean supply
3. Part 3 Decarbonisation so far, and the hard parts

   The world has cut the carbon intensity of its energy for two centuries, mostly without trying. Cutting total emissions is another matter. This part looks at what has been achieved, why electricity is leading, why four basic materials are so hard to clean up, and which popular beliefs about energy have repeatedly misled investors and governments.

   • Carbon intensity has fallen for two centuries while emissions kept rising
   • Electricity is where decarbonisation is furthest ahead
   • Ammonia, steel, cement and plastics are the hard core of emissions
   • Energy myths have repeatedly misled policy and investment
4. Part 4 Carbon dioxide, climate and the paths ahead

   Fossil fuels matter for climate because they move carbon out of rocks, where it was stored for millions of years, into the atmosphere. This part places that flow within the planet's great element cycles, sets out what is known about CO2 and warming, and summarises what the IEA's latest scenarios imply for emissions and temperatures.

   • Humans now rival the planet's natural flows of carbon, nitrogen and sulfur
   • The physics of CO2 warming has been known for over a century
   • The IEA's 2025 scenarios span roughly 1.5 to 3 C of warming
5. Wrap-up Key terms, try it in the table, final quiz, sources