High accuracy line intensities for carbon dioxide

All CO2 remote sensing activity, from both the ground and space, relies on monitoring how CO2 absorbs light. All this monitoring is therefore heavily dependent on understanding the absorption properties of the CO2 molecule which is usually obtained by measurements performed in the laboratory. In particular the accurate knowledge of the strength of individual absorption lines is crucial to determining how much CO2 is present and allowing the atmospheric data to be interpreted. Without high accuracy values for line intensities, reliable CO2 retrievals are simply not possible. Particularly with their emphasis on variation of CO2 concentrations with time, current missions and proposed missions require CO2 line intensities to be determined to significantly better than 1% accuracy if they are to fulfill their stated goals: intensities accurate to better than 0.5% are really required. Current line intensities measured in the laboratory simply do not gives this level of accuracy: most are accurate to about 5% with a few high quality measurements being good to 1 - 3%. Hence current cO2 retrievals values are limited by the available laboratory data. The aim of this proposal is to provide an accurate theoretical solution to the problem of CO2 line intensities based on the application of high accuracy, first principles quantum mechanical calculations for the intensities and experimental data for the line positions. The resulting new lists of CO2 transition intensities will be made widely available and, in particular, used to inform atmospheric databases which are used for the majority of atmospheric applications of molecular spectroscopy.

This is potentially a high impact project. The major impact will be for the atmospheric remote sensing community as the project will allow them to significantly improve CO2 retrievals with the consequence improvement in CO2 monitoring, modeling and. hopefully, control. The improvement in CO2 line intensities proposed here is essential to properly exploit actual or planned missions and programmes aimed explicitly at recording CO2 concentrations in the Earth's atmosphere.
Accurate CO2 data is important for a whole variety of other applications including planetary atmospheres (Mars, Venus, Exoplanets) and elsewhere in the Universe. It will also contribute to projects on space craft re-entry and other applications of CO2 data which will certainly appear during the course of the project.
The line intensities (and associated line list) generated in this project will be distributed widely and vigorously to maximise its potential impact. It will be made available via (atmospheric) databases HITRAN and GEISA; via BADC and via
web portals such as the Virtual Atomic and Molecular Data Centre (VAMDC), and my own exomol.com website.

My work on molecular spectroscopy regularly gets extensive national and international press coverage. I use topics from this work (including ones relating to atmospheric physics) as the basis of popular talks which I give to schools and other non-specialist groups.