Farmers in the Midwestern United States grew so much corn in the 20th century that they unintentionally changed the local climate.
This emerges from a recent study that found that increases in corn and soybean production caused significant changes in summer precipitation and temperature compared to decades ago.
The phenomenon affected cooler summers and increased rainfall and even masked the regional effects of global warming.
Farmers in the Midwestern United States grew so much corn in the 20th century that they unintentionally changed the local climate. File photo
"We have been interested for some time in how changes in land use can affect the climate," said Elfatih Eltahir, Breene M. Kerr Professor of Hydrology and Climate.
"It's an independent problem of carbon emissions."
In the study recently published for the journal Geophysical Research Letters, the team analyzed regional weather changes as corn and soybean production increased; Between 1950 and 2009, researchers say that corn increased fourfold, while soybeans doubled.
An increase in plant density means that more moisture is released into the atmosphere as the plants open their pores (stoma) to "breathe" carbon dioxide.
A recent study has shown that increased corn and soybean production compared to decades ago has caused significant changes in summer rainfall and temperature. The above map shows the number of corncobs produced in the second half of the 20th century
This extra moisture cooled the air and increased the rain, the researchers said.
The team noted that regional temperature and precipitation patterns have changed significantly, Eltahir said.
"A region in the Midwest became colder, which was a surprise."
The researcher adds that "there is a robust data set that shows significant changes in temperature and precipitation."
According to research, the average summer rains in the Midwest increased by about 15 percent in the last half of the 20th century.
The above map compares the precipitation in the late 20th century compared to the previous half. His map shows deviations in precipitation compared to the previous half century. Areas with elevated precipitation are shown in green, while areas with reduced precipitation are shown in brown
The change in average summer temperatures is shown in the map above, with temperatures above average in red and lower than average in blue. The researchers say the results show a correlation between increased crop production, higher rainfall and lower temperatures
By contrast, the summer temperature dropped by about half a degree Celsius. At the same time, the humidity increased.
"During the twentieth century, the US Midwest experienced regional climate change more in line with what we would expect from land-use change than from other power plants," Eltahir said.
"The acreage has not increased very much during this period, but crop production has increased significantly, resulting in a sharp increase in crop yields," says Ross Alter, a recent postgraduate student at MIT.
WHY ARE CLIMATE MODELS DIFFICULT TO PREDICT?
The main problem with climate models is the uncertainty.
In particular, the so-called equilibrium climate sensitivity has caused the scientists headaches.
This is a highly influential measure that describes how much the planet warms up when carbon dioxide doubles and the Earth's climate adapts to the new state of the atmosphere.
Studies have found a wide range of possibilities for this key measure – somewhere between 1.5 and 4.5 ° C and 3 ° C.
Most scientists are trying to narrow the ECS by looking at historical warming events.
Over the last 25 years, the United Nations International Panel on Climate Change (IPCC), the supreme authority in climate science, has set a "likely" range of 1.5 ° C to 4.5 ° C.
A warming of less than 1 ° C is "extremely unlikely" and more than 6 ° C is classified as "very unlikely".
However, some scientists deny this figure.
Researchers say the results show that increasing agricultural yields on existing farmland can have climate effects at a regional level.
This could be a useful strategy in some locations to mitigate the local effects of global warming, Eltahir said.
The earnings boom at the end of the 20th century is unlikely to be seen.
"This was a 20th century phenomenon, and we expect nothing similar in the 21st century," says Eltahir.
In the future, "will not be the advantage of these regional moderators."