Over the deade the authors examined (2000 to 2010), the average level of the gas (CO2) in the atmosphere went up by 22 parts-per-million. And the time series shows a steadily rising trend in its impact, layered on top of the seasonal changes. By the end of that period, the gas was retaining an extra 0.2 Watts for every square meter of the Earth’s surface compared to the start.
Still, it seems worth noting that the continued increase in greenhouse energy retention measured during this time coincides with a period where the Earth’s surface temperatures did not change dramatically. All that energy must have been going somewhere.
The authors started in the 2000 La Nina, and ended at the 2010 El Nino – when troposphere temperatures were half a degree warmer. Then they noticed that there was slightly more downwelling longwave radiation, which they blamed on increased absorption from the increase in CO2.
The increase in DLWR was due to the warmer troposphere during the El Nino. Warmer air emits more longwave radiation. The higher concentration of CO2 will also emit more DLWR radiation, but that is not due to increased absorption. I don’t know how scientists can get any more clueless than that.