Carbon budgets for assessing adequacy

Mainstreaming Equity in the Preparation and Assessment of National Contributions

Ulriikka Aarnio, CAN Europe

Cumulative emissions determine warming

• Different types of targets, variable reference levels and base years all aim to address amount of cumulative emissions in the atmosphere.

• Even ambitious point targets, such as zero by 2050, do not alone guarantee that warming can be limited to 2°C or 1.5°C.

• Necessary to ensure that overall emissions over time are kept within a budget.

IPCC AR5 and carbon budgets

• The IPCC’s 5th Assessment Report WGI for the first time also includes carbon budget numbers:

• IPCC AR5 WG1 SPM: Limiting the warming caused by anthropogenic CO2 emissions alone with a probability of >33%, >50%, and >66% to less than 2°C since the period 1861–1880, will require cumulative CO2 emissions from all anthropogenic sources to stay between 0 and about 1570 GtC (5760 GtCO2), 0 and about 1210 GtC (4440 GtCO2), and 0 and about 1000 GtC (3670 GtCO2) since that period, respectively. These upper amounts are reduced to about 900 GtC (3300 GtCO2), 820 GtC (3010 GtCO2), and 790 GtC (2900 GtCO2), respectively, when accounting for non-CO2 forcings as in RCP2.6. An amount of 515 [445 to 585] GtC (1890 [1630 to 2150] GtCO2), was already emitted by 2011.

IPCC AR5 and carbon budgets

• Current global annual emissions are in the range of 13 GtC.

• This leaves an available >66% 2°C budget of 236 GtC after 2014.

• With stable emissions of 13 GtC per year this budget is used up in less than 20 years. With BAU emissions even faster.

• With current trends one third of this remaining budget will be used up in the next 5-6 years

• Most important that emissions peak and decline very quickly. Already before 2020.

• More we use now, less we have in the future to spend.

Slide: Reto Knutti

>66% 2°C >90% 2°C >66% 1.5°C

>90% 1.5°C

Co2 budget

GtC

1000 730 750 548

Co2eq budget

GtC

790 577 593 433

GtC used by 2011

-515 -515 -515 -515

GtC used 2011-2014

-39 -39 -39 -39

GtC left after 2014

236 GtC 23 GtC 39 GtC -121 GtC

Budgets available

* Budgets for >90% for 2°C and >66% and >90% for 1,5°C are translated to Co2eq in GtC using the same formula (79% share of Co2) as in the budget of >66% for 2°C by the IPCC.

EU pathway proposal*

*assuming that the EU is looking into at least >66% likelihood for below 2°C

Pathway to zero by 2050

Conclusions

• Peak and fast decline before 2020 necessary.

• Transparency and quantifiability of INDCs critical.

• Challenge requires international cooperation.

• Fairness and equity needed in order to enable this cooperation.

Thank you.