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What is Carbon Budget?
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A carbon budget is the cumulative amount of carbon dioxide (CO₂) that humanity can emit while
limiting the rise in global average temperature to no more than 1.5 °C.
In other words, it’s the “balance” of carbon we have available.
What happens if we exceed it? The Earth heads toward irreversible climate collapse.
To put it another way: imagine you have a 10 GB monthly data plan on your phone. If you watch too many videos at the beginning of the month,
you’ll run out of data by month’s end and be unable to do anything online.
A carbon budget works the same way—if we use too much now, future generations will have no carbon “headroom” left.
“A carbon budget is the total cumulative amount of carbon dioxide that humanity can emit in order to limit the rise in global average temperature to a specified threshold
(e.g., below 1.5 °C).”
- Intergovernmental Panel on Climate Change (IPCC) -
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Who and How Is the Carbon Budget Determined?
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Scientists run simulations on supercomputers to calculate the carbon budget.
The IPCC regularly publishes updated budget ranges based on data contributed by researchers worldwide.
The size of the budget depends on factors such as:
• The emissions already released to date
• The warming effects of non-CO₂ greenhouse gases (methane, nitrous oxide, etc.)
• Earth’s climate sensitivity to additional warming
• The capacity of forests, oceans, and other sinks to absorb CO₂
To learn more about the IPCC, see: ⇊ What Is the Intergovernmental Panel on Climate Change? |
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What Happens If We Exceed the Budget?
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If the carbon budget is exceeded,
the global average temperature will rise sharply.
Remember the 2020 Australian wildfires?
Forest area six times the size of the Korean Peninsula burned, and around three billion animals perished.
Approximately 60,000 koalas—famous for their cute appearance—lost their lives.
Images of thirsty koalas stumbling toward people’s water bottles shocked the world.
According to UNEP’s 2024 Emissions Gap Report, if current reduction rates continue, by the end of this century the average temperature could rise by up to 3.1 °C above pre-industrial levels.
That means extreme heatwaves, sea-level rise, massive wildfires, and widespread famine would become the norm.
Already experienced climate disasters:
• Australia (2020): Wildfires killed around three billion animals, including koalas
• Europe (2022): Heatwaves caused over 60,000 deaths
• Pakistan (2022): Floods displaced 33 million people and caused US $30 billion in damage
All of these are consequences of global warming—and at the root lies ‘exceeding the carbon budget.’
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How Much Budget Remains?
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According to the IPCC’s 2021 report, the carbon budget to stay below 1.5 °C is roughly 400–500 Gt CO₂.
The problem is that global CO₂ emissions in 2024 are expected to reach an all-time high.
Fossil fuels alone (coal, oil, gas) are projected to account for about 37.4 Gt CO₂.
At this rate, the budget could be exhausted in roughly 7–8 years. The IPCC warns:
“Global CO₂ emissions must decrease by
at least 45% from 2010 levels by 2030.”
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Global Emissions Overview
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How much greenhouse gas was emitted worldwide in 2023?
A staggering 57.1 Gt CO₂e. Let’s see which sectors contribute most:
(Source: UNEP, Emissions Gap Report 2024)
• Energy sector: ~68% of total emissions
▶ Industry: 11%
▶ Transport: 15%
▶ Buildings: 6%
▶ Fuel production: 10%
Road vehicles dominate transport emissions, with aviation also significant.
• Industrial processes: ~9%
▶ Particularly chemical, metal, and cement production.
• Agriculture and land-use change: ~18%
▶ Agriculture (livestock, rice cultivation): 11%
▶ Deforestation and other land-use changes: 7%
• Waste management: ~4%
▶ Primarily from solid and liquid waste treatment.
This breakdown highlights the critical importance of energy conservation and shifting to renewables.
Which countries emit the most?
(Source: UNEP, Emissions Gap Report 2024)
• China: 16,000 Mt CO₂e (30%)
• United States: 5,970 Mt CO₂e (11%)
• India: 4,140 Mt CO₂e (8%)
• European Union: 3,230 Mt CO₂e (6%)
• Russia: 2,660 Mt CO₂e (5%)
• African Union (all member states): 3,190 Mt CO₂e (6%)
• Brazil: 1,300 Mt CO₂e (2%)
• Least Developed Countries (45 nations): 1,720 Mt CO₂e (3%)
• Other G20 members (excluding African Union): 6,410 Mt CO₂e (12%)
The largest emitters are generally economically advanced nations,
while those suffering the worst impacts—climate-vulnerable countries—emit far less and lack resources to adapt.
To learn more about climate-vulnerable countries, see: ⇊ What Are Climate-Vulnerable Countries? |
Less powerful nations are more exposed to heatwaves, floods, and droughts.
Achieving climate justice requires global cooperation and, in particular, greater responsibility, support, and action from advanced countries.
To learn more about climate justice, see: ⇊ |
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How Is the International Community Responding?
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The clock on the climate crisis is ticking fast.
Governments and international bodies are continually raising their emissions-reduction targets:
1. Paris Agreement
• Limit global warming to well below 2 °C, pursuing efforts toward 1.5 °C
• Countries set Nationally Determined Contributions (NDCs)
2. EU Emissions Trading System (ETS)
• Caps total emissions; companies exceeding their allowance must buy permits
• Encourages corporate transitions to cleaner practices
3. UK Carbon Budget Law
• Sets five-year emissions reduction targets
• Aims for a 68% reduction by 2030
• Promotes EV infrastructure expansion and bans on new internal-combustion vehicle sales
4. U.S. Inflation Reduction Act (IRA)
• Allocates over US $433 billion over ten years for climate action
• Supports renewables, EVs, and carbon-capture technologies
The climate crisis is no longer a matter of choice but of survival.
To learn more about carbon pricing, see: ⇊ Taxing Carbon: An Introduction |
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10 Actions We Can Take
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1. Use a carbon-footprint calculator.
2. Reduce meat consumption and increase plant-based foods.
3. Choose public transit or biking over driving alone.
4. Adopt electric or shared vehicles.
5. Support companies using renewable energy.
6. Use energy-efficient appliances and LED lighting.
7. Research and buy from brands with strong emissions-reduction commitments.
8. Combine deliveries and minimize long-distance shipping.
9. Hold virtual meetings instead of traveling for business.
10. Embrace zero-waste and minimalist lifestyles.
Global CO₂ emissions are hitting record highs each year—a clear warning that our carbon budget is rapidly depleting.
The international community must act swiftly and decisively, with nations accelerating green transitions through renewables,
efficiency improvements, and carbon-capture innovation.
But above all, individual, ongoing action matters.
Small habits, multiplied across the globe, can extend the Earth’s “time.”
To learn more about the Doomsday Clock, see: ⇊ “Doomsday Clock: Only 100 Seconds to Midnight” |
“At current emission rates, our carbon budget will be exhausted within a few years. Immediate reductions are essential.”
- Dr. James Hansen, Climate Scientist -
Written by Sharon Choi
Director of Planning
Sunhak Peace Prize Secretariat
Learn More : (Intergovernmental Panel on Climate Change)? ▶ What are Countries Vulnerable to ▶ Levying a Tax even on Carbon! |
References and Sources : • IPCC. Special Report: Global Warming of 1.5°C (2018), Sixth Assessment Report (2021)Intergovernmental Panel on Climate Change (IPCC). • UNEP. Emissions Gap Report 2024United Nations Environment Programme (UNEP). • UNEP. Adaptation Gap Report 2023United Nations Environment Programme (UNEP). • Global Carbon Project. Global Carbon Budget 2023 • IEA. CO₂ Emissions in 2023International Energy Agency (IEA). • Bulletin of the Atomic Scientists. Doomsday Clock Statement 2024 |