A General Carbon Budget

This document outlines our allocaton of a Carbon Budget for Teignbridge and it's annual rate of reduction. How this is derived depends on its intended purpose:

• If it is to comply with the law, then the legal minimum is the 6 carbon budgets in the Climate Change Act. This means that it reflects the UK'sNationally Determined Contributions (NDCs), which are essentially territorial emissions, derived from GHG emissions within UK borders excluding:
  • International aviation and shipping
  • Imported goods and services
• If it is to stand a reasonable chance of avoiding the worst effects of climate change, (i.e. reaching a Climate tipping point) then all emissions caused by the UK's decisions need to be taken into account. These also need represent the UK's fair share of global emissions. This statement raises some questions:
  • What is a fair share?
  • What should be the temperature limit?
  • How certain do we need to be that the limit (tipping point) won't be exceeded?

The legal minimum is significantly lower and therefore easier to achieve, it can reasonably be determined at a local authority level because territorial emissions are published at that level. The Climate Change Committee (CCC) assumed a 50% probability of achieving 1.5℃, but the pathway they have adopted puts a large share of the reduction after 2037. Given the catastrophic consequences, we believe this approach is risky and therefore irresponsible. It also does not fully adhere to the Paris agreement on mitigating climate change.

In its 6 th Carbon budget report, the CCC has stated that consumption emissions would add a further 50% to UK’s territorial emissions. Government published data on the UK’s consumption emissions show that in the past few years this has increased to ~70% more than territorial emissions. This has meant the the UK's territorial emissions as a proportion of global emissions have dropped from ~1.1% to 0.9%. Furthermore the UK is historically responsible for emissions for longer than other countries, many argue that the UK should therfore be responsible for more than its current proportion of global emissions.

To strike a balance between the above conflicting criteria and objectives, we have decided not to allocate historical emissions. However, we have decided to allocate a budget for Teignbridge and rate of reduction based on IPCC’s AR6 scenario for a 67% likelihood of not exceeding the 1.5℃ temperature rise, with the UK’s share of global emissions set at 1%.

A spreadsheet has recently been produced to derive a budget based on the Climate Change Act, we will include the calculation for this at a later date.

The remainder of this document establishes the rate of reduction for emissions on a global basis, for several temperature rises and probabilities of not exceeding these. The model adopted is simply a compound reduction. The rate of reduction is determined only by the IPCC budget, any subsequent emissions and the starting rate of consumption.

Although other greenhouse gasses (GHG) are extrapolated from CO₂ these do not influence the rate of reduction.

What are global emissions?

Most countries now report their CO₂ emissions. The world totals are shown in the table below. Emissions are in Gt CO₂. GHG emissions can be estimated by addition of 20%.

Reference Data Supplement to the Global Carbon Budget 2022. The table above is extracted from National Fossil Carbon Emissions 2022. This is only emissions from fossil fuels, LULUCF, other sources and sinks are not taken into account.

IEA also estimate global fossil fuel emissions and have estimated that in 2022 emissions increased by 320MtCO₂ , they have a slightly lower figure for 2021. We have estimated 2022 by adding 320Mt CO₂ to our 2021 figure.

The budget - IPCC Report AR6

Includes table SPM.2, which gives IPCC's estimated global CO₂ budget remaining from the start of 2020, for different temperatures and probabilities.

The table below is drawn from table SPM.2, budgets are in Gt CO₂

IPCC recommends that we should be limiting global warming to no more than 1.5℃C above pre-industrial levels, with a probablilty of 67%.

How long have we got at the current rate

If emissions remained at their levels the limit would be reached in the years in the following table:

In this scenario if emissions don't fall, then the temperature will continue to rise. In order to limit temperature rise, net emissions must fall to zero.

Fixed percentage annual reduction starting at difference years

The rate at which we need to reduce increases the later we leave starting. The following tables give required percentage reductions to stay within the temperature limit for each year.

Calculator for Fixed percentage annual reduction calculator

This model calculates for a given temperature limit and probability what annual rate of reduction on current emissions would be needed to stay within the limit. The remaining period is divided into two parts:

• Before the start year UK consumption emissions are reduced by actual or estimated consumption emissions from the consumption emissions table above.
• At and after the start year UK consumption emissions are reduced by a fixed percentage each year.

If the year reduction starts is before 2020 consumption emissions for each preceding year are added to the budget before the reduction rate is calculated.

If the year reduction starts is after 2020 consumption emission for each missing year are deducted from the budget before the reduction rate is calculated.

+Press this button to expand the first few years data for the graph above.
+Press herer for the mathematical basis of the budget calculations

The UK's 6 carbon budgets

These are a legal commitment made under the Climate Change Act 2009. They set a budget for each 5 year period from 2008-2012 onwards. So far 6 carbon budgets have been set.