A reader recently wrote to ask us about our November 17 article: “Satellite Detects Human Contribution to Atmospheric CO2.”

“Hello, I read on the site that CO 2 concentrations are higher in some areas and lower in others. Is the reason for this that the higher zones are near CO 2 sources such as heavily populated areas? I always thought gas spread evenly in a container.”

We asked Janne Hakkarainen, a researcher at the Finnish Meteorological Institute and co-author of the study that used OCO-2 data to make satellite-based maps of human emissions of carbon dioxide. Launched in July 2014, NASA’s Orbiting Carbon Observatory-2 (OCO-2) was designed to give scientists comprehensive, global measurements of carbon dioxide in the atmosphere.

Hakkarainen wrote: “Carbon dioxide is indeed well mixed in the atmosphere. This means that if we look at the CO 2 concentrations globally, the value is about 400 ppm everywhere.” (That’s 400 parts per million.)

Findings from the UN Intergovernmental Panel on Climate Change warn about the consequences of rising CO 2 concentrations: “Any CO 2 stabilisation target above 450 ppm is associated with a significant probability of triggering a large-scale climatic event.”

“In our recent research paper, we developed a methodology to derive regional CO 2 anomalies, which means that we remove from individual CO 2 values the regional CO 2 median,” wrote Hakkarainen. “When these anomalies are averaged over time, the map highlights the CO 2 signal that is not yet mixed and still close to the emission source. The idea is to average out the ‘CO 2 weather’ or ‘transport,’ illustrated nicely in this NASA computer simulation (below).”

Another reader asked: “Can someone explain the high CO2 content over the Idaho panhandle and the large area at sea off the Oregon-California border.”

“The Idaho Panhandle anomalies could be related to biogenic sources or fire emissions,” wrote Hakkarainen. For example, NOAA’s CarbonTracker system showed positive fluxes (not including fossil fuel emissions) in that area in 2014.

Tags: carbon dioxide