The Currency Metaphor

What if we treated carbon like money? Not as an abstract environmental concern, but as a concrete, finite resource we manage through budgets, trade-offs, and conscious spending decisions?

This is the core idea behind my “CO2 Currency” approach to personal carbon management.

How It Works

Setting the Annual Budget

Based on climate science and fair-share principles:

• Global carbon budget for 1.5°C target
• Divide by population = ~2-3 tonnes per person per year
• My current budget: 5 tonnes (transitional, aiming for 3)

Monthly Allocation

5 tonnes/year = 417kg/month “to spend”

Tracking Expenditure

Every activity has a carbon “price”:

Real-time Balance

Like a bank account, I track:

• Monthly budget: 417kg
• Spent to date: Updated weekly
• Remaining: What’s left for the month
• Annual projection: On track or overspending?

The Psychology

Makes Trade-offs Visible

“Should I fly to this conference?” becomes:

• Cost: 250kg for international flight
• Remaining budget: 180kg this month
• Trade-off: That’s 6 months of home heating

Suddenly the decision isn’t abstract – it’s concrete. Do I value this conference more than staying warm for half a year?

Encourages Planning

Just like financial budgeting:

• High-carbon months (winter heating, travel) need planning
• Savings from low-carbon months can offset planned splurges
• Unexpected expenses (emergency flights) impact later months

Reveals True Costs

Seeing carbon as currency exposes how carbon-intensive modern life is:

• A transatlantic flight (~1,500kg) = 3 months’ budget
• A new car (~6,000kg embedded) = More than a year
• Daily latte in disposable cup (~20kg/month) = 5% of budget

Implementation

Tools Used

1. Spreadsheet - Main tracking (monthly categories)
2. Conversion factors - Standard CO2e calculations
3. Energy monitor - Real-time home usage
4. Travel log - Distance × emissions factors
5. Purchase tracker - Estimated embedded carbon

Monthly Review

First Sunday of each month:

• Calculate previous month’s actual spend
• Compare to budget
• Adjust current month if needed
• Project year-end total

Annual Reconciliation

January audit against actual footprint measures accuracy of tracking.

Challenges

Incomplete Data

Hard to know embedded carbon in:

• Food (especially eating out)
• Services (haircuts, healthcare)
• Digital infrastructure (cloud storage, streaming)

Solution: Estimate conservatively, revise annually with better data.

Temptation to Inflate Budget

Easy to justify: “Everyone else uses 8 tonnes, so 5 is good enough!”

Counter: Climate science doesn’t negotiate. 2-3 tonnes is the target, 5 is already a compromise.

Month-to-month Variability

Winter heating makes some months inevitably higher.

Solution: Annual budget with monthly averaging, accepting seasonal variation.

Unexpected Benefits

Motivation

Watching the “balance” provides ongoing feedback. Like seeing your savings grow, watching carbon “savings” accumulate is motivating.

Prioritisation

Forces clarity about what matters:

• Virtual conference? Free (carbon-wise)
• Train to European city? Affordable
• Transatlantic flight? Major expense, better be worth it

Conversation Starter

Explaining the system to colleagues and students opens discussions about individual vs. systemic action.

Limitations

Individual Action Insufficient

Personal carbon budgeting can’t:

• Fix systemic infrastructure problems
• Eliminate embedded emissions in necessities
• Address historical responsibility
• Replace policy and regulation

Privilege

Ability to choose lower-carbon options often requires:

• Money (heat pumps, EVs, organic food)
• Time (train vs. plane)
• Flexibility (work-from-home)
• Location (cycling infrastructure, public transport)

Not everyone can “budget” their way to low carbon.

The Bigger Picture

CO2 Currency is a personal tool, not a climate solution. But it:

1. Makes abstract concrete - Numbers you can’t ignore
2. Enables rational decisions - Trade-offs visible
3. Tracks progress - Improvement measurable
4. Maintains awareness - Constant carbon consciousness

Combined with advocacy for systemic change, it’s part of a portfolio of actions.

Try It Yourself?

If you want to experiment:

1. Calculate your current footprint (see CO2 audits)
2. Set a target (2-5 tonnes depending on starting point)
3. Convert to monthly budget
4. Track major activities
5. Review monthly
6. Adjust and learn

Don’t aim for perfection. Aim for conscious awareness and gradual reduction.

Reflection

Treating carbon as currency isn’t just a metaphor – it changes how I experience decisions. Every choice has a visible price.

Sometimes I “overspend.” That’s okay. The point isn’t perfection, it’s mindfulness.

And unlike money, you can’t earn more carbon budget. The planet’s is fixed. This makes the metaphor even more apt – and urgent.