Miller Magazine Issue 137 May 2021

32 MILLER / may 2021 NEWS Despite important agricultural advancements to feed the world in the last 60 years, a Cornell-led study shows that global farming productivity is 21% lower than it could have been without climate change. This is the equivalent of losing about seven years of farm productivity increases since the 1960s. The future potential impacts of climate change on global crop pro- duction has been quantified in many scientific reports, but the historic influence of anthropogenic climate change on the agricultural sector had yet to be modeled. Now, a new study provides these insights: “Anthropogenic Climate Change Has Slowed Global Agricultural Productivity Growth,” published in Nature Climate Change, was led by economist Ariel Ortiz-Bobea, asso- ciate professor in theCharles H. Dyson School of Applied Economics and Management. “We find that climate change has basicallywiped out about seven years of improvements in agricultural productivity over the past 60 years,” Ortiz-Bobea said. “It is equivalent to pressing the pause button on productivity growth back in 2013 and experiencing no improvements since then. Anthropogenic climate change is already slowing us down.” The scientists and economists developed an all-encompassing econometric model linking year-to-year changes in weather and pro- ductivity measures with output from the latest climate models over six decades to quantify the effect of recent human-caused climate change on what economists call “total factor productivity,” a measure capturing overall productivity of the agricultural sector. Ortiz-Bobea said they considered more than 200 systematic varia- tions of the econometric model, and the results remained largely con- sistent. “When we zoom into different parts of the world, we find that the historical impacts of climate change have been larger in areas al- readywarmer, includingparts of Africa, LatinAmerica andAsia,” he said. Humans have already altered the climate system, Ortiz-Bobea said, as climate science indicates the globe is about 1 degree Celsius warm- er than without atmospheric greenhouse gases. “Most people perceive climate change as a distant problem,” Ortiz-Bobea said. “But this is some- thing that is already having an effect. We have to address climate change now so that we can avoid further damage for future generations.” Ortiz-Bobea and Robert G. Chambers, professor of production eco- nomics at the University of Maryland, have been pioneering new pro- ductivity calculations in agriculture to include weather data that has not been addressed historically, aiming to bring new accuracy to climate models. “Productivity is essentially a calculationof your inputs compared to your outputs, and inmost industries, the onlyway to get growth iswith new inputs,” Chambers said. “Agricultural productivity measurement hasn’t historically incorporated weather data, but we want to see the trends for these inputs that are out of the farmer’s control.” David Lobell, professor of earth system science at Stanford, said that the results show clearly that adaption efforts must look at the whole supply chain, including labor and livestock. “They also show that even as agriculture becomes more mechanized and sophisticated, the sen- sitivity to weather does not go away,” he said. “This is counter-intuitive for most people, and we need a deeper understanding of why.” “My sense is that we are just gettingbetter at eliminating all thenon-weather constraints on production, but we need to scrutinize various possible explanations,” said Lobell, who examines the impact of climate change on crop production and food security. “This study is a big leap beyond the traditional focus on a few major grain crops,” he said. “By looking at thewhole system– the animals, the workers, the specialty crops – we can see that the entire agricultural economy is quite sensitive toweather. It seems that in agriculture, prac- tically everything gets harder when it’s hotter. Climate change cut global farming productivity 21% since 1960s Ariel Ortiz-Bobea Charles H. Dyson School Applied Economics and Management