Gilbert Compo, a scientist at NOAA’s University of Colorado Cooperative Institute for Research in Environmental Sciences used a physically-based data assimilation system, 20th Century Reanalysis (20CR) to evaluate the accuracy of global warming theories. He used barometric pressure records, ocean surface temperatures, and other factors independent of land-based reading to gather his data.
Compo and his scientists showed an increase from 1901 to 2010 of 0.99 degrees Celsius, which is greater than some land-based instrument datasets, though it is smaller than some others. 20CR analysis demonstrated that warming since 1952 was 0.78 degrees Celsius. Using only barometric pressure as a starting point, Campo and his team realized that they were able to produce hourly, day-to-day variations in temperature.
Often, land-based historical readings are not trusted because weather stations in rural areas in the early part of the 20th century were affected by the growing cities around them, making it appear as though a warming trend was taking place when it might not have been global warming at all. Changes in weather observation stations’ surroundings, according to climate scientists, can have a direct effect on the data currently being gathered. Trees being replaced by concrete and urban development are the primary culprits.
However, some experts posit that these land use changes are not significant enough to undermine that data that proves that climate change is real, but the experts do acknowledge that naysayers of global warming won’t change their minds based on this data.