NASA satellite data has shown that anywhere from 10 to 40 percent of improvements in key U.S. crop yields since 1940 could potentially be attributed to increased atmospheric carbon dioxide due to human activity, according to a new paper from Columbia University’s Charles A. Taylor and Wolfram Schlenker.
The authors noted that their findings are “on the very high end of the range found in the literature.”
“Taylor and Schlenker’s numbers are 10–100 times as large as previous estimates,” Richard S.J. Tol, a professor in the Department of Economics at the University of Sussex, told The Epoch Times via email.
Taylor and Schlenker arrived at their estimates using three separate modeling strategies. In addition, they ran sensitivity checks to rule out potential confounds, including economic activity, other pollutants, and their assumptions about the precise relationship between carbon dioxide levels and crop yields.
Their models were based on data from 2015 through 2020 collected by NASA’s Orbiting Carbon Observatory-2 (OCO-2) satellite, which they replicated with NOAA’s CarbonTracker system. They also used county-level data on corn, soybeans, and winter wheat yields from the U.S. Department of Agriculture’s (USDA) National Agricultural Statistics Service.
Taylor and Schlenker found that an increase of 1 part per million of carbon dioxide raised corn yields by 0.5 percent, soybean yields by 0.6 percent, and wheat yields by 0.8 percent.
“Put another way, yields may have increased 1–2 [percent] per year due to CO2 fertilization in recent years,” the authors wrote, noting the positive correlation between increased atmospheric carbon dioxide and greater agricultural yields in recent decades.
They also noted that the potentially dramatic fertilizing effect of atmospheric carbon dioxide might not be so unexpected, given how it’s used in actual agricultural greenhouses.
“The gas has long been pumped into greenhouses to spur photosynthesis and increase the yield of horticultural crops. Optimal CO2 concentrations of 900 [parts per million] have been suggested, which is over twice current ambient levels,” the authors wrote.
Taylor and Schlenker’s approach contrasts with field- and laboratory-based studies on carbon dioxide enrichment. The authors argued that such experiments “are limited in the extent to which they reflect real-world growing conditions in commercial farms at a large geographic scale.”
Some research on carbon dioxide and plant growth has suggested that increased carbon dioxide may affect plant nutritional quality in both positive and negative ways.
A 2019 meta-analysis of 57 articles on carbon dioxide and vegetable growth concluded that elevated atmospheric carbon dioxide raised fructose, glucose, total soluble sugar, total antioxidant capacity, total phenols, total flavonoids, ascorbic acid, and calcium in plants while lowering protein, nitrate, magnesium, iron, and zinc.
The research has sparked a range of reactions on Twitter.
“If you’re an [agriculture] person, you’ll want to look at this study. They find shockingly large CO2 fertilization effects,” wrote Michael Roberts, an economist at the University of Hawaii at Manoa.
“A short time series though—geospatial variation in CO2 probably not well measured prior to this satellite data and time series confounded by technical change,” he continued, later adding that “someone ought to compare the satellite data to the ground-based measures.”
In an email exchange with The Epoch Times, Roberts confirmed that he doesn’t believe their confounding due to technical change is likely to be an issue in Taylor and Schlenker’s study, adding that any measurement error “could go either way,” and that the satellite data used by Taylor and Schlenker are likely superior to ground-based measurements with respect to accuracy.
“Translation: although farmable regions may shift if there’s a slight warming effect, higher CO2 emissions may result in HIGHER crop yields,” wrote Mark B. Spiegel, managing member of Stanphyl Capital.
The paper’s first author, Taylor, said: “We reiterate that climate change will have a large negative impact on agriculture in aggregate, especially in places exposed to extreme heat. And higher CO2 may even lower food nutrition. But the countervailing fertilization effect should also be taken into account.”