Carbon Budget Remaining Calculator Formula
Understand the math behind the carbon budget remaining calculator. Each variable explained with a worked example.
Formulas Used
Budget Remaining
remaining_gt = budget_total_gt - used_budgetYears Until Exhausted
years_left = (budget_total_gt - used_budget) / annual_emissions_gtBudget Already Used
pct_used = used_budget / budget_total_gt * 100Variables
| Variable | Description | Default |
|---|---|---|
budget_total_gt | Total Carbon Budget from 2020(Gt CO2) | 500 |
annual_emissions_gt | Current Annual Emissions(Gt CO2/yr) | 40 |
years_elapsed | Years Elapsed Since 2020(years) | 6 |
used_budget | Derived value= annual_emissions_gt * years_elapsed | calculated |
How It Works
The Global Carbon Budget
The carbon budget is the total amount of CO2 that can still be emitted while keeping global warming below a specific temperature target.
Formula
Remaining Budget = Total Budget - (Annual Emissions x Years Elapsed)
Years Left = Remaining Budget / Annual Emissions
The IPCC estimates that for a 50% chance of staying below 1.5°C, the remaining budget from 2020 was about 500 Gt CO2. At current rates of ~40 Gt/year, this budget is rapidly shrinking.
Worked Example
Starting budget of 500 Gt CO2 from 2020 with 40 Gt/year emissions, 6 years later.
- 01CO2 used = 40 x 6 = 240 Gt CO2
- 02Remaining = 500 - 240 = 260 Gt CO2
- 03Years left = 260 / 40 = 6.5 years
- 04Budget used = 240 / 500 x 100 = 48.0%
Frequently Asked Questions
What is a carbon budget?
A carbon budget is the maximum cumulative amount of CO2 that can be emitted while still having a reasonable chance of limiting warming to a specific temperature target.
Is the 1.5°C budget already exhausted?
It is very close. At current emission rates, the budget for a 50% chance of staying below 1.5°C may be exhausted by the late 2020s.
Does the budget account for other greenhouse gases?
Carbon budgets typically focus on CO2 but assume certain trajectories for methane and other gases. Higher non-CO2 emissions reduce the effective CO2 budget.
Ready to run the numbers?
Open Carbon Budget Remaining Calculator