Guest essay by Eric Worrall
Ariel Ortiz-Bobea, an economist at Cornell University, claims that all of the CO2 and global warming we’ve added to the atmosphere is affecting crop growth and agricultural yields, and we are only keeping up with better farming practices. But how does Ariel explain the global greening of wilderness regions observed by NASA?
Rapid global warming affects farm productivity, according to a study
Research shows that rising temperatures have acted as a handbrake on the agricultural yield of crops and livestock since the 1960s
Oliver Milman @olliemilman
Fri 2 Apr 2021 02.00 AEDT
The climate crisis is already affecting the production of global agricultural systems. Productivity is much lower than if humans had not warmed the planet quickly, new research has shown.
Advances in technology, fertilizer use, and world trade have enabled food production to keep pace with the world’s booming population since the 1960s, albeit with gross inequalities that still leave millions of people undernourished.
According to the new study published in Nature Climate Change, rising temperatures during this period slowed the productivity of crops and livestock in agriculture. Productivity has actually dropped 21% since 1961, compared to the fact that the world would not have been exposed to man-made warming.
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“The impact is already bigger than I thought,” said Ariel Ortiz-Bobea, an economist at Cornell University who led the research.
“It was a big surprise for me. I worry that research and development in agriculture will take decades to achieve higher productivity. The projected temperature rise is so rapid that I don’t know if we’ll keep up with it. “
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The abstract of the study;
Anthropogenic climate change has slowed global growth in agricultural productivity
Ariel Ortiz-Bobea, Toby R. Ault, Carlos M. Carrillo, Robert G. Chambers, and David B. Lobell
abstract
Agricultural research has promoted productivity growth, but the historical impact of anthropogenic climate change (ACC) on that growth has not been quantified. We are developing a robust econometric model of the effects of weather on global total agricultural factor productivity (TFP) and combining this model with counterfactual climate scenarios to assess the impact of past climate trends on TFP. Our baseline model shows that ACC has reduced global agricultural TFP by about 21% since 1961, a slowdown equivalent to the loss of productivity growth over the past 7 years. In warmer regions such as Africa, Latin America, and the Caribbean, the effect is much more severe (a decrease of ~ 26–34%). We are also finding that global agriculture has become more vulnerable to ongoing climate change.
Read more: https://www.nature.com/articles/s41558-021-01000-1
Back in the real world, NASA reports that the world is not only turning green thanks to anthropogenic CO2, but that the additional vegetation has a strong cooling effect on the surface of the planet.
A new study reports that increased vegetation growth in the past few decades, known as “Greening Earth”, has had a strong cooling effect on land due to the increased efficiency of heat and water vapor transfer into the atmosphere.
A new study published in the journal Science Advances, titled “Biophysical Effects of Greening the Earth, Controlled Largely by Aerodynamic Drag,” reports that the entire land surface without the cooling effect of increased green cover has increased much in recent decades would have been warmer. The study used high quality satellite data from NASA’s MODIS sensors and NCAR’s state-of-the-art numerical earth system model.
Satellite observations show widespread increasing trends in the leaf area index (LAI) known as earth greening. However, the biophysical effects of this greening on land surface temperature (LST) remain unclear. Here we quantify the biophysical effects of the greening of the earth on the LST from 2000 to 2014 and unravel the contributions of various factors using a physically based attribution model. We find that 93% of the global vegetation area has a negative sensitivity of LST to an increase in LAI on an annual basis, especially in semi-arid wood vegetation. Taking into account the LAI trends (P ≤ 0.1), 30% of the global vegetation area is cooled by these trends and 5% is heated. Aerodynamic drag is the dominant factor in controlling the biophysical effects of greening: the increase in LAI leads to a decrease in aerodynamic drag and thereby favors increased turbulent heat transfer between land and atmosphere, especially the latent heat flow. Credit: Chi Chen
The greening of the land in the first fifteen years of the 21st century meant additional heat dissipation (2.97 × 1021 J) from the surface, which corresponds to five times the total energy that humans generated and consumed in 2015 (5.71 × 1020 J ). This cooling effect caused by greening was twenty-five times stronger than the warming effect caused by tropical deforestation.
“In the fight against climate change, plants are the lonely defenders. Stopping deforestation and the large-scale green planting of trees could be a simple but insufficient defense against climate change. “Said the lead author Dr. Chi Chen a former Ph.D. Student at Boston University, now postdoctoral researcher at DOE’s Lawrence Berkeley National Lab.
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Read more: https://www.nasa.gov/feature/greening-of-the-earth-mitigates-surface-warming
Ariel seems to suggest that increasing agricultural yields are due to better farming practices to overcome the damage caused by global warming. However, this does not explain the massive global greening of wilderness areas observed by NASA. Unfortunately, the full study is chargeable, but if the underlying trend were increasing climate damage, which is mitigated by better agriculture, surely only farms would be more environmentally friendly.
Warm temperatures are not a threat to agriculture. Even if summer temperatures rise beyond the tolerance of some crops, the solution will be planted a little earlier. In my district there are many plants that are grown commercially with temperate climates, plants that would never survive the summer heat. Farmers in my district plant potatoes, carrots, cabbage, celery and other temperate vegetables at the beginning of winter and harvest them in spring.
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