He has now updated his research using data from previous studies that relied on satellite and aircraft measurements of emissions above oil and gas fields. (climatecentral.org)
So, a sea ice estimate for a region constructed from shipping reports in the 1920s might not be directly comparable to an estimate for the same region from the 1940s made from aircraft measurements. (globalwarmingsolved.com)
The study used aircraft measurements where they circled upwind and downwind of potential sources, but they only sampled during two days. (dotearth.blogs.nytimes.com)