High accuracy CO${}_2$ line intensities determined from theory and experiment

Atmospheric CO${}_2$ concentrations are being closely monitored by remote sensing experiments which rely on knowing line intensities with an uncertainty of 0.5%\ or better. Most available laboratory measurements have uncertainties much larger than this. We report a joint experimental and theoretical study providing rotation-vibration line intensities with the required accuracy. The {\it ab initio} calculations are extendible to all atmospherically important bands of CO${}_2$ and to its isotologues. As such they will form the basis for detailed CO${}_2$ spectroscopic line lists for future studies.