Details of Award
NERC Reference : NE/P014844/1
Quantifying the cumulative carbon emissions consistent with a 1.5C global warming (TCRE1.5)
Grant Award
- Principal Investigator:
- Professor P Friedlingstein, University of Exeter, Engineering Computer Science and Maths
- Co-Investigator:
- Professor D Wallom, University of Oxford, Engineering Science
- Grant held at:
- University of Exeter, Engineering Computer Science and Maths
- Science Area:
- Atmospheric
- Marine
- Terrestrial
- Overall Classification:
- Unknown
- ENRIs:
- Global Change
- Science Topics:
- Climate & Climate Change
- Biogeochemical Cycles
- Biogeochemical Cycles
- Abstract:
- Global warming is directly related to greenhouse gases emissions from human activities, essentially burning of fossil fuel, with carbon dioxide being the dominant greenhouse gas. Recent studies have demonstrated that the sum over time of all CO2 emissions (cumulative emissions) largely determines global mean surface warming. Any given level of warming is associated with a specific range of cumulative CO2 emissions, larger cumulative emissions inducing larger warming. Keeping global warming below 1.5 degree Celsius (1.5C) above pre-industrial level will hence require future cumulative CO2 emissions to be below a limited budget. Knowing that remaining carbon budget with as little uncertainty as possible is key for decision on greenhouse gases mitigation policies. It will inform us on how soon and how strong CO2 emissions reduction needs to be implemented. In it's latest assessment, the intergovernmental Panel on Climate Change reported that limiting the warming below 1.5C since the pre-industrial would require cumulative CO2 emissions to stay below 615GtC. Given that, up to now, humanity already emitted about 555GtC, was is left for the future is only about 60GtC. That would be 6 years from now as current global CO2 emissions are around 10GtC per year. We argue that this IPCC estimate might not be realistic. It is hardly consistent with the observed warming and associated emissions over the 20th century. For present-day, historical emissions (555GtC) contributed to a warming of about 1C. How could the next 60GtC contribute to 0.5C? We think that this estimate of the remaining carbon budget (60GtC) is quite certainly an underestimate, which has important policy consequences for efforts to meet a 1.5C goal. It could negatively affect the mitigation policy process, giving the impression that the 1.5C is not achievable any more. In this project we will investigate the main reasons that could explain why the remaining CO2 budget, as given in IPCC, might be biased. First, natural climate variability is important. The models used to derive this estimate fail to fully simulate the observed warming and carbon cycle. In particular, the majority of these models did not simulate the lower than average rate of warming over the last 15 years. The models overestimate the current warming, some of them having a present-day warming already near 1.5C, while the observed warming is about 1C above pre-industrial. The implication is that those models will significantly underestimate the remaining CO2 emissions before they would reach 1.5C. Second, although the cumulative budget is about CO2 only, non-CO2 agents such as methane or aerosols also play a role in the estimate of the remaining budget. Assuming large reduction of aerosols in the future, as in the scenario used by IPCC for example would lead to a significant warming, leaving then less room for CO2 emissions before we reach 1.5C. The IPCC estimate is based on one single future scenario (called RCP8.5), which is representative of a world without any climate mitigation, warming being well above 2C by 2100, but with significant air quality policies. Such scenario is probably not ideal for the estimate of CO2 emissions consistent with a 1.5C world. Third, related to the two points above, the numerous climate and carbon cycle feedbacks that operate in the Earth System need to be fully diagnosed in specific scenarios aiming to remain below 1.5C where global temperature and atmospheric CO2 stabilize, not from unmitigated scenarios with exponential increase in atmospheric CO2 and increasing climate change. Our project will investigate these sources of potential biases in order to provide a robust assessment of the maximum amount of CO2 humankind could potentially emit in the future while limiting global warming to 1.5C.
- NERC Reference:
- NE/P014844/1
- Grant Stage:
- Completed
- Scheme:
- Directed (RP) - NR1
- Grant Status:
- Closed
- Programme:
- One and a Half Degrees
This grant award has a total value of £100,406
FDAB - Financial Details (Award breakdown by headings)
| DI - Other Costs | Indirect - Indirect Costs | DA - Investigators | DI - Staff | DA - Estate Costs | DA - Other Directly Allocated | DI - T&S |
|---|---|---|---|---|---|---|
| £5,242 | £33,272 | £10,510 | £37,114 | £6,962 | £290 | £7,016 |
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