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Detection of changing radiative forcing over the recent decades.


Problems to be solved
Considerable uncertainties still exist in the magnitude of some of the main forcing factors which causes climatic change. There is a need to better quantify these factors e.g. those due to greenhouse gases, aerosols, and stratospheric ozone and to solar processes.
Scientific objectives and approach
The project aims to estimate the magnitude of temporal changes/variations in external forcing of climate, and to compare both the timing and the magnitude of the detected forcing anomalies with known and hypothesised variations in external forcing. Two different techniques to obtain the forcing will be used and compared, namely temporal changes in 6 and 24 forecast errors, i.e. forecast increments, and temporal changes in initial tendency errors obtained by assimilating the slow atmospheric normal modes obtained from re-analysis into a state-of-the-art climate model. The re-analysis data sets, which will be used, are the ERA15, ERA40 and the GEO-1 and GEO-2 data. The climate model to be used is the ECHAM model. Using re-analysis data, model tendency errors will be analysed to establish real forcing fields and to quantify forcing from processes not included in the model, i. e. stratospheric ozone, volcanic aerosols and desert dust. As a second step an improved ECHAM model, including parametrization of the processes mentioned above, will be used to assimilate the re-analysis data and the results will be used to estimate the performance of the parameterisation schemes and the upgraded model. It is intended also to use this technique in a reverse mode to estimate e.g. concentrations of aerosols from volcanic eruptions. With the estimates of real forcing due to the various processes as far back in time as over the last 40 years the aim is to establish improved (insofar the accuracy of the data permits) estimates of dust/aerosol concentrations during dust/aerosol events. Such estimates are of particular interest for the earlier part of the period, where satellite observations of dust and aerosol loads are not available. In the same way, on a longer time scale, it will be investigated whether effects related to the 11-year sunspot cycle and solar processes of shorter duration and of stratospheric ozone depletion over the period can be quantified. Based on the above the various forcing estimates will be used to isolate the global warming signal from the increase in greenhouse gases (including water vapour), and to quantify to what extent greenhouse forcing has been offset by other forcing or processes during the period.
Expected impacts
The project contributes to detection and attribution of climate change and its causes and its results could have important policy implications a and impacts. The data sets produced and the model development work will contribute to the development of better climate models and climate change scenarios.

Funding Scheme

CSC - Cost-sharing contracts


Lyngbyvej 100
2100 Koepenhagen

Participants (2)

Bundesstra¯e 55
20146 Hamburg
Ramat Aviv
69978 Ramat - Aviv