In the Northern Hemisphere, there's a strong seasonal cycle of vegetation. Each year in the Northern Hemisphere, levels of atmospheric carbon dioxide drop in the summer as plants "inhale," then climb again as they exhale after the growing season. During the last 50 years, the size of this seasonal swing has increased by as much as half, for reasons that aren't fully understood. Now a team of researchers has shown that agricultural production may generate up to a quarter of the increase in this seasonal carbon cycle, with corn playing a leading role.

Source: Boosts in productivity of corn and other crops modify Northern Hemisphere carbon dioxide cycle