Background
The negotiating countries participating at the COP have already proposed a national contribution to global climate policy (Intended Nationally Determined Contribution, INDC) or will do so in the next months. Two central questions arise in this context:
- How do the individual country pledges compare among each other and, related to this, how do they compare against a global climate policy following generally accepted guidelines?
- Are the ambitions of the world community sufficiently high to reach the generally agreed targets of maximum global warming?
To contribute to this debate, we take a sufficiently stringent global carbon budget up to 2050 as a reference case. The global budget is distributed among the parties following different general principles. Taking account the most discussed equity principles and feasibility constraints; we provide a climate calculator that compares different distributions of such a carbon budget. For a longer discussion and presentation of the different calculation methods, we refer to the paper “Prices vs. equity in international climate policy: A broad perspective” by Lucas Bretschger and Janick Mollet (2015), CER-ETH Working Paper Series, ETH Zurich.
Calculation choices
In order to use this calculator, the interested user has to define some variables which are common to all three proposals and some parameters which are specific to some of the proposals.
First, you are invited to pick one of three scenarios for a global carbon dioxide budget in line with the expected temperature change until 2050 based on Meinshausen et al (2009) and similar to the pathways used by the Climate Equity Reference Calculator.
| Scenario | Global 2000-2050 CO2 budget, Z | Probability of temperature increase < 2°C |
|---|---|---|
| Strict | 1000 GtCO2 | 75% |
| Medium | 1440 GtCO2 | 50% |
| Soft | 1600 GtCO2 | > 33% |
Second, the user is also allowed to pick the number of countries or the amount of global emission covered by such an international climate agreement; countries are ranked according to their emissions in 2010. You either choose the number of countries, the second field, or the percentage of worldwide cumulative emissions covered, the third field. For example, if you think that the budget should cover the 60 most polluting countries, the percentage of global CO2 emissions will be 96%, and vice versa.
Third, our calculator presents three different ways of calculating the country distributions of a global carbon budget based on:
The equity-based proposal by Bretschger (2013) allocates the budget according to:
- Four different equity principles: Ability to pay (α), cost sharing (β), technical contribution (γ), and technical development (δ). Based on the weighting of these principles (the Greek letters), we calculate a country specific fairness index to allocate the global carbon budget.
- Responsibility factor: to account for historic responsibility, the user chooses a responsibility factor that defines the proportion of previous emissions that is deducted from the 1990-2050 budget and also chooses the reference year of past emission.
The global carbon tax follows the proposal from Weitzman (2013) and sets a globally uniform tax keeping emissions below the chosen budget until 2050 (see detailed explanation). We convert the implied reductions into country CO2 budgets.
The egalitarian proposal developed by the BASIC expert group (2011) is a special case of the equity principles method assigning equal weights to every human on the planet. It also accounts for the responsibility factor: the proportion of previous emissions (1990-2014) that is deducted from the 1990-2050 budget (see detailed explanation).