The data include historical atmospheric concentrations as well as concentrations for the RCPs and their extension to Extended Concentration Pathways—ECPs. Data for a wide range of substances is provided, including gases controlled under the Kyoto Protocol, ozone depleting substances controlled under the Montreal Protocol, and a wide range of aerosols and particles. The Integrated Assessment Modeling Consortium IAMC is the scientific community organization that coordinated the review and release of the four RCPs and is coordinating additional modeling exercises and intercomparisons.
The web site details the climate model protocol for this project. In order to ensure a smooth transition of land use change from historical to future across the base year, and provide a consistent set of land use inputs to climate models, a harmonization step was necessary.
Additional details are available from this web site. The four RCPs used a common set of historical emissions data to initialize the integrated assessment models. Those historical data are available for download. The climate modeling community requested additional scenario guidance out to for long term climate response research. The references in the table below provide links to original data sets as posted by these groups. See the references section for additional documentation.
Smith and Wigley Clarke et al. It is likely one of the factors that gave rise to the use of RCP8. This means that while they factor in different ways society could develop in the future, they do not account for any future concerted climate mitigation efforts or existing commitments, such as the Kyoto Protocol. This suggests that the authors say no reason to consider RCP8.
The researchers emphasise this point in their paper, showing how the emissions in each scenario compared to the range found in the energy modelling literature at the time. The figure below, taken from their paper, shows each RCP compared to the 90th percentile dark grey and 98th percentile light grey of energy modeling scenarios in the literature that had been previously developed by researchers.
CO2 emissions between and in RCP8. The researchers found that overall radiative forcing in RCP8. However, they also emphasise that this is not the only scenario ever produced that results in emissions and radiative forcing this high; around 40 scenarios with a similar forcing level exist in the energy modelling literature.
So, the emissions scenario used to generate RCP8. While it was by no means considered an impossible outcome, it was also not considered to be more or less likely than any other no-policy baseline scenario — the vast majority of which resulted in lower emissions. But it is surely not the only one, and in terms of the level of GHG emissions, it is not the most likely. One can only get that high by a combination of factors, e.
In the paper detailing the RCP8. The high-end nature of the RCP8. In the Shared Socioeconomic Pathways SSPs were finally published — about five years later than originally envisioned by Richard Moss and colleagues. The SSPs integrate different sets of population, economic growth, and other socioeconomic assumptions into future emissions scenarios.
They consider both a wide range of potential no-policy baseline scenarios, as well as how different mitigation scenarios could be attained under different socioeconomic pathways. The SSPs contain a range of baseline scenarios spanning between 5. They also specifically consider mitigation scenarios where forcing is limited to 6. Both the 8. The new 8. The 7. The 8. It was a scenario that the IAMs had some trouble generating; of the five socioeconomic pathways examined, only one — SSP5 — could produce a scenario with emissions that high.
In contrast, an intermediate baseline SSP2 only produces a forcing signal of about 6. There are several reasons for the difference between the new and old RCP8. The new scenario is also based on very different socioeconomic assumptions; while RCP8.
One particular aspect of both the RCP8. Reaching the CO2 emissions in these scenarios requires a large-scale increase in coal use — with 6. The figure below shows the global primary energy mix in in each of the different baseline scenarios examined in the SSP database.
The timeseries of coal use in these models is shown in the figure below, which includes all baseline and mitigation SSP scenarios — shown as thin lines — with the marker scenarios being used in CMIP6 highlighted with solid lines. With global coal use having declined slightly since its peak in , it is hard to envision a world where coal expands this dramatically in the future even in the absence of new climate policies.
This is particularly true given the falling prices of alternative energy technologies in recent years. At the same time, however, it is important to recognise that predicting future emissions is inherently extremely uncertain. There are two main sources for these contrasting views about RCP 8. The size of anthropogenic emissions depends upon factors such as population growth and technology change, all of which are built into RCP 8.
In carbon feedback loops natural systems respond to warming by releasing additional carbon or in some cases by reducing the natural drawdown of carbon from the atmosphere which leaves more carbon in the atmosphere. Examples of these feedback loops include permafrost thaw and intensification of methane release by tropical wetlands. Because of uncertainties in these carbon warming feedback loops, any particular level of emissions could lead to different atmospheric concentrations depending upon the strength of the eventual feedback loop.
For example, a level of emissions that is typically associated with a relatively high level of atmospheric carbon concentrations for example RCP 7 could in fact lead to an even higher level of atmospheric concentration for example RCP 8. Researchers have looked at what happens when climate models are run using an emissions scenario, rather than concentration scenarios, to partially account for these feedbacks and found that CO2 concentrations and the resulting warming were significantly higher than predicted by a concentration pathway analysis.
In sum, RCP 8.
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