Framing climate goals in terms of cumulative CO2-forcing-equivalent emissions
Abstract:
The relationship between cumulative CO2 emissions and CO2-induced warming is determined by the Transient Climate Response to Emissions (TCRE), but total anthropogenic warming also depends on non-CO2 forcing, complicating the interpretation of emissions budgets based on CO2 alone. An alternative is to frame emissions budgets in terms of CO2-forcing-equivalent (CO2-fe) emissions – the CO2 emissions that would yield a given total anthropogenic radiative forcing pathway. Unlike conventional ‘CO2-equivalent’ emissions, these are directly related to warming by the TCRE and need to fall to zero to stabilise warming: hence CO2-fe emissions generalise the concept of a cumulative carbon budget to multi-gas scenarios. Cumulative CO2-fe emissions from 1870-2015 inclusive are found to be 2900 ± 600GtCO2-fe, increasing at a rate of 67 ± 9.5GtCO2-fe/year. A TCRE range of 0.8–2.5° Cper 1,000 GtC implies a total budget for 0.6° C of additional warming above the present decade of 880–2,750 GtCO2-fe, with 1,290 GtCO2-fe implied by the CMIP5 median response, corresponding to 19 years' CO2-fe emissions at the current rate.ENSO relationship to summer rainfall variability and its potential predictability over Arabian Peninsula region
Reliable low precision simulations in land surface models
A simple pedagogical model linking initial-value reliability with trustworthiness in the forced climate response
Abstract:
Using a simple pedagogical model, it is shown how information about the statistical reliability of initial-value ensemble forecasts can be relevant in assessing the trustworthiness of the climate system’s response to forcing.
Although the development of seamless prediction systems is becoming increasingly common, there is still confusion regarding the relevance of information from initial-value forecasts for assessing the trustworthiness of the climate system’s response to forcing. A simple system which mimics the real climate system through its regime structure is used to illustrate this potential relevance. The more complex version of this model defines “REALITY” and a simplified version of the system represents the “MODEL”. The MODEL’s response to forcing is profoundly incorrect. However, the untrustworthiness of the MODEL’s response to forcing can be deduced from the MODEL’s initial-value unreliability. The nonlinearity of the system is crucial in accounting for this result.