A series of climate change policy cards produced to coincide with COP 20 in Lima, which provide up-to-date evidence for policy questions in this area.
Policy card 1: Which emissions pathways give a high probability of limiting global average warming to below 2°C?
The long term temperature goal of the UNFCCC aims to limit global average warming above pre-industrial levels to no more than 2°C. A range of future emissions pathways to achieve this goal have been suggested by numerous academic studies but more clarity is needed on what this means for the range of acceptable emissions in 2020, 2030 and 2050.
Policy card 2: How much future damage do we avoid by limiting average warming to below 2°C?
Evidence from climate impact models shows us that high emissions pathways correspond to severe local impacts, with more frequent and severe extreme weather events and effectively irreversible change. This leads to the question of how much potential damage can be avoided by following a pathway that limits global warming to below various temperature levels.
Policy card 3: How can we decarbonise the global energy system, what technologies are needed and how much will it cost?
Energy modelling shows that deep decarbonisation of the energy system over the 21st century is achievable with technologies currently commercially available or at a pre-commercial demonstration phase. There is now an urgent need to understand which technologies and emissions pathways over the coming decades are technically and economically feasible.
Policy card 4: How much carbon can we emit without warming exceeding 2°C?
A key finding in the most recent IPCC assessment was that there is an approximate linear relationship between the total amount of carbon emitted into the atmosphere and the eventual level of warming. This means that choosing a long-term goal in terms of temperature also corresponds to a total amount of carbon. A challenge for the scientific community is to narrow down the uncertainty in the size of this allowable global carbon budget.
Policy card 5: Avoiding dangerous climate change
Further information on the AVOID 2 research programme.
- Uncertainty in carbon budgets is large but in many studies it is often not adequately treated. Understanding this is vital to the feasibility of the long-term aim of limiting warming to 2°C. Technically this warming limit is still within reach.
- The IPCC database of emission pathways is a very useful resource but must be used with care. The data highlights the urgency in the need to peak global emissions if lower levels of warming are to be achieved. It also shows that a large fraction of the mitigation scenarios aiming to limit warming to less than 2°C rely on artificially removing CO2 from the atmosphere – often called negative emissions.
- AVOID 2 has been carrying out a new inter-comparison of integrated assessment models and the latest work also shows the potential additional costs of delaying the global emissions peak year, this is particularly acute for the lower levels of warming. The costs are minimised by early mitigation action.
- There is the potential to avoid some but not all future impacts from climate change; typically between 20 and 70% of the impacts we considered could be avoided by limiting warming to 2°C instead of following a pathway to 4°C.Even where impacts are not avoided urgent mitigation can provide a delay and allow more time for adaptation.