Fossil Fuels and Carbon Emissions: The Largest Driver of Warming

Fossil Fuels and Carbon Emissions: The Largest Driver of Warming

Editorial advisor: Mr. John Smith, Specialist Environment, PhD in Environmental Engineering.

Coal, oil, and natural gas are the remains of ancient plants and organisms, transformed by heat and pressure over millions of years. Burning them releases the carbon stored in that ancient organic matter as carbon dioxide, along with energy. That energy built the modern world — powering factories, transport, heating, and electricity — and the carbon dioxide it released is now the largest human driver of climate change.

Fossil fuels still supply the majority of global primary energy. That fact explains both why emissions are so hard to cut quickly and why cutting them is the central task of climate policy. Every sector that depends on fossil fuels must find an alternative, or capture and store the emissions, if warming is to be limited.

How emissions grew

For most of human history, energy came from wood, muscle, wind, and water. The Industrial Revolution changed that by making coal cheap and abundant for steam engines, iron, and later electricity. Oil followed for transport, and natural gas expanded for heating, electricity, and industry. Global CO2 emissions from fossil fuels rose from a small fraction of today's level in 1900 to tens of billions of tonnes per year today.

Growth has not been uniform. Early industrial economies — now high-income countries — account for most historical emissions, because they burned fossil fuels for longest. In recent decades, emissions growth has shifted toward rapidly industrialising economies, while per-person emissions remain highest in wealthy countries and among wealthy people everywhere. This history shapes debates about fairness: who should cut fastest, who should pay for transition, and how developing countries can grow without repeating the high-carbon path.

Emissions are usually counted in two ways. Production-based accounting attributes emissions to the country where fuels are burned. Consumption-based accounting attributes them to the country where goods are ultimately consumed, which shifts some emissions from manufacturing countries to importing countries. Both views are valid; they answer different questions, and honest reporting should say which is being used.

Where emissions come from today

Energy production is the largest source. Electricity and heat generation, dominated in many countries by coal and gas, account for a large share of global CO2. Coal is the most carbon-intensive fuel per unit of energy, followed by oil, then natural gas. Switching from coal to gas reduces emissions per unit of electricity, but gas still emits CO2 and leaks methane, so it is a partial step, not a destination.

Transport is the next major block, dominated by road vehicles, with aviation and shipping adding significant shares. Unlike electricity, transport has been slower to decarbonise because vehicles are dispersed, long-lived, and — for planes and ships — harder to electrify directly. Electric vehicles, cleaner fuels, public transport, and reduced travel demand all play roles, but no single measure solves transport alone.

Industry emits CO2 both from burning fuels for heat and from chemical processes, especially cement and steel. Cement releases CO2 when limestone is heated to make clinker; steel traditionally uses coal as both fuel and chemical reducing agent. These "hard-to-abate" sectors need new processes, alternative materials, recycling, and in some cases carbon capture, rather than simple fuel switching.

Buildings emit CO2 through heating, cooling, and electricity use. In cold climates, heating dominates; in hot climates, cooling demand is growing rapidly as incomes rise and temperatures climb — a feedback in which warming itself drives more energy use.

Natural gas: bridge or trap?

Natural gas is often called a bridge fuel because it emits roughly half the CO2 of coal per unit of electricity. In places where it replaces coal quickly, it can cut emissions in the short term. But the bridge argument has limits. Gas infrastructure lasts decades, creating lock-in. Methane leaks during extraction, transport, and distribution can erase much of the climate benefit, especially over short timescales. And a bridge that is never exited becomes a destination.

The IPCC's assessment is clear: pathways that limit warming to 1.5 degrees Celsius require deep, rapid cuts in all fossil fuels, including gas, not merely a switch from coal to gas. Gas may play a transitional role in some systems, but long-term plans built on expanding gas are inconsistent with those pathways.

What cutting fossil-fuel emissions actually involves

Cutting emissions is not only about using less energy, though efficiency helps enormously. It is about replacing the energy source. For electricity, that means wind, solar, hydro, nuclear, and storage, plus grids capable of handling variable supply. Costs of wind and solar have fallen dramatically, making them the cheapest new electricity in many regions, but deployment speed, grid connections, and storage remain constraints.

For transport, it means electrifying what can be electrified, improving public transport and urban design so fewer car journeys are needed, and developing sustainable fuels for aviation and shipping where batteries are impractical. For industry, it means green steel and cement processes, material efficiency, and circular economy approaches that reduce demand for virgin materials.

It also involves managing the transition fairly. Fossil-fuel workers, communities, and countries dependent on fossil-fuel revenue face real disruption. A transition that ignores them risks political backlash and hardship; a transition that plans retraining, diversification, and support is both fairer and more durable. This is the idea behind a "just transition," now central to climate policy discussions.

Carbon capture: help, not a substitute

Carbon capture and storage (CCS) captures CO2 from industrial processes or power plants and stores it underground. It can help in sectors where emissions are hard to eliminate, such as cement. Direct air capture removes CO2 directly from the atmosphere. Both technologies exist, but they are expensive, energy-intensive, and currently capture only a tiny fraction of global emissions.

CCS does not justify continued expansion of fossil fuels. Capturing a portion of emissions from a new coal plant still leaves substantial emissions, and the energy and cost of capture are significant. The IPCC treats CCS as a complement to deep emissions cuts, not a replacement for them. Readers should be sceptical of claims that capture alone solves fossil-fuel emissions.

The scale of the task

The remaining carbon budget — the total CO2 that can still be emitted while keeping a reasonable chance of limiting warming to 1.5 or 2 degrees Celsius — is shrinking rapidly at current emission rates. This is why scientists emphasise the current decade: emissions must peak and then fall steeply, not merely slow their growth.

That scale can feel daunting, but it also clarifies priorities. The largest, fastest cuts come from stopping new coal, accelerating renewable electricity, electrifying transport and heating, improving efficiency, and ending methane leaks. Individual choices matter, but they operate within systems — grids, transport networks, and industrial processes — that only policy and investment can transform at the required speed.

Fossil fuels built prosperity, but their waste product — carbon dioxide — is now reshaping the climate. The task is not to deny that history, but to build an energy system that delivers prosperity without the same waste.

Sources

• IPCC, Sixth Assessment Report, Synthesis Report — https://www.ipcc.ch/report/ar6/syr/
• International Energy Agency — https://www.iea.org/
• US Environmental Protection Agency, Greenhouse Gas Emissions — https://www.epa.gov/ghgemissions
• NASA, Causes of Climate Change — https://science.nasa.gov/climate-change/causes/
• United Nations, Climate Change — https://www.un.org/en/climatechange