Global Warming Facts: Study Finds Increased Crop Production Is Causing Rise in Greenhouse Gas Carbon Dioxide

A new study suggests that increased agricultural crop production in the last five decades to meet the fast growing food demands of the world's population has changed the levels of atmospheric carbon dioxide (CO₂), reports Tech Times.

Christopher Kucharik, Nelson Institute associate professor of Agronomy and Environmental Studies, and a team of researchers claim in a study published Nov. 19 in the journal Nature that intensive crop production is at least 25 percent responsible for the seasonal increase in carbon dioxide.

Carbon dioxide is a heat trapping gas recognized by scientists as a significant contributor of global warming.

Ground and aircraft-based measurements were used by the research team to determine that the seasonal amplitude of Northern Hemisphere atmospheric CO₂ concentrations has increased by about 50 percent over the past 50 years.

In the spring and summer, plants absorb carbon dioxide and use it to convert the sun's energy into food. The plants release the carbon dioxide back into the atmosphere in autumn and winter. Northern Hemisphere crop production has grown by 240 percent since the 1960s, resulting in an increase in the carbon dioxide being released into the atmosphere, according to the study.

"Here we use production statistics and a carbon accounting model to show that increases in agricultural productivity, which have been largely overlooked in previous investigations, explain as much as a quarter of the observed changes in atmospheric CO₂ seasonality," the researchers wrote in the study.

Only 6 percent of the Northern Hemisphere vegetated areas is cropland, and yet it is responsible for the 50 percent rise in the seasonality cycle of the greenhouse gas, Kucharik and fellow researchers found.

"That's a very large, significant contribution, and 2/3 of that contribution is attributed to corn," Kucharik said. "Corn once again is king, this time demonstrating its strong influence on the seasonal cycle of atmospheric CO₂."

Another study published Nov. 19 in the journal Nature supports these findings.

University of Maryland atmospheric scientist Ning Zeng and a team of researchers also discovered that increased crop production contributes to advanced seasonal shifts in carbon dioxide cycles.

"The intensification of agriculture (the Green Revolution, in which much greater crop yield per unit area was achieved by hybridization, irrigation and fertilization) during the past five decades is a driver of changes in the seasonal characteristics of the global carbon cycle," Zeng and his colleagues wrote. "Our analysis of CO₂ data and atmospheric inversions shows a robust 15 per cent long-term increase in CO₂ seasonal amplitude from 1961 to 2010, punctuated by large decadal and interannual variations."