The overall plan as outlined in the Statement of Work consists of the scientific evaluation of existing stratospheric CDRs, the maturation of relevant ESA and ESA-TPM data products to make them of “climate quality”, the use of these matured data to generate new CDRs for stratospheric temperature and ozone (which are the most mature data sets), and laying the groundwork for the generation of new CDRs for stratospheric water vapour and aerosol (which are less mature and emerging global data sets). The technical approaches to develop and deliver these data products are in agreement with the appropriate standards and international best scientific practise. The principal challenge of the work is to statistically characterize the differences between the different data sets, based on a sound physical knowledge of potential causes of those discrepancies, so that they can be merged in a physically consistent, defensible manner. Otherwise the act of merging will generate temporal inhomogeneities and can lead to spurious long-term changes. For CDRs, although an adequate accuracy is essential, the stability of the observation has pre-eminence, so the focus is not on improving the absolute calibration but rather on creating homogeneous CDRs that will be of use to the international scientific community. Through the process, we will also be able to provide feedback to the international bodies (e.g. GCOS, WMO, GRUAN, WOAP) setting standards for CDRs.