Warming Oceans And Agricultural Expansion Driving U.S. Midwest Summer Warming Hole

[bluewave]

This is a major reason why the Dust Bowl record highs in this region haven’t been able to be exceeded with global warming causing record highs everywhere else. Our land practices during the Dust Bowl were responsible for greatly amplifying the drought and heat. So the expansion of corn production has created a localized cooling in these areas relative to the rest of the world.
 

https://www.science.org/content/article/america-s-corn-belt-making-its-own-weather

 

The United States’s Corn Belt is making its own weather

By Kimberly HickokFeb. 16, 2018 , 12:05 PM

The Great Plains of the central United States—the Corn Belt—is one of the most fertile regions on Earth, producing more than 10 billion bushels of corn each year. It’s also home to some mysterious weather: Whereas the rest of the world has warmed, the region’s summer temperatures have dropped as much as a full degree Celsius, and rainfall has increased up to 35%, the largest spike anywhere in the world. The culprit, according to a new study, isn’t greenhouse gas emissions or sea surface temperature—it’s the corn itself.

This is the first time anyone has examined regional climate change in the central United States by directly comparing the influence of greenhouse gas emissions to agriculture, says Nathan Mueller, an earth systems scientist at the University of California (UC), Irvine, who was not involved with this study. It’s important to understand howagricultural activity can have “surprisingly strong” impacts on climate change, he says.

The Corn Belt stretches from the panhandle of Texas up to North Dakota and east to Ohio. The amount of corn harvested in this region annually has increased by 400% since 1950, from 2 billion to 10 billion bushels. Iowa leads the country for the most corn produced per state.

To see whether this increase in crops has influenced the region’s unusual weather,researchers at the Massachusetts Institute of Technology in Cambridge used computers to model five different 30-year climate simulations, based on data from 1982 to 2011. First, they compared simulations with high levels of intense agriculture to control simulations with noagricultural influence. Unlike the real-life climate changes, the control simulations showed no change in temperature or rainfall. But 62% of the simulations with intense agriculture resulted in temperature and rainfall changes that mirror the observed changes, the team reports this week in Geophysical Research Letters.

 

Map of the central United States, showing changes in rainfall during the last third of the 20th century. Areas of increased rainfall are shown in green, with darker colors representing a greater increase.

MASSACHUSETTS INSTITUTE OF TECHNOLOGY 

The team then compared its results to historical global simulations from the World Climate Research Programme (WCRP), an international program for the coordination of global climate research sponsored by the International Council for Science, the World Meteorological Organization, and the Intergovernmental Oceanographic Commission of UNESCO. WCRP’s models take into account greenhouse gas emissions and other natural and humanmade influences, but do not consider agricultural land use. When researchers ran the numbers for the Corn Belt, the global models fell short of reality: They predicted both temperature and humidity to increase slightly, and rainfall to increase by up to 4%—none of which matches the observed changes.

Other climate simulations that use sea surface temperature variation didn’t match observed changes, either. Those simulations matchedhistorical data until 1970; after that, the simulations predicted temperatures to keep increasing, rather than decreasing as they did in reality. This is a strong indication that agriculture, and not changing sea surface temperature, caused the regional changes in climate during the last third of the 20th century, the researchers say.

“The [influence] of agriculture intensification is really an independent problem from greenhouse gas emissions,” says Ross Alter, lead author of the study and now a meteorologist with the U.S. Army Corps of Engineers in Hanover, New Hampshire. In fact, Alter says, heavy agriculture likely counteracted rising temperatures regionally that might have otherwise resulted from increasing greenhouse gas emissions. One other place that shows a similar drop in temperatures, he notes, is eastern China, where intensive agriculture is widespread.

But how does agriculture cause increased rainfall and decreased temperatures? The team suspects it has to do with photosynthesis, which leads to more water vapor in the air. When a plant’s pores, called stomata, open to allow carbondioxide to enter, they simultaneously allow water to escape. This increases the amount of water going into the atmosphere and returning as rainfall. The cycle may continue as that rainwater eventually moves back into the atmosphere and causes more rainfall downwind from the original agricultural area.

Rong Fu, a climate scientist at UC Los Angeles, agrees with the team’s assessment. She alsothinks that though human influence might be “greater than we realize,” this regional climate change is probably caused by many factors,including increased irrigation in the region.

“This squares with a lot of other evidence,” says Peter Huybers, a climate scientist at Harvard University, who calls the new study convincing. But he warns that such benefits may not last if greenhouse gas emissions eventually overpower the mitigating effect of agriculture.

Alter agrees, and says it’s unlikely that the large increases in U.S. crop production during the 20th century will continue. Other scientists have voiced concern that agricultural production could soon be reaching its limit in many parts of the world. 

“Food production is arguably what we’re more concerned about with climate change,” Mueller says. And understanding how agriculture and climate will continue to affect one another is crucial for developing projections for both climate and agricultural yields. “It’s not just greenhousegasses that we need to be thinking about.” 


https://news.wisc.edu/irrigated-farming-in-wisconsins-central-sands-cools-the-regions-climate/
 

New research finds that irrigated farms within Wisconsin’s vegetable-growing Central Sands region significantly cool the local climate compared to nearby rain-fed farms or forests.

Irrigation dropped maximum temperatures by one to three degrees Fahrenheit on average while increasing minimum temperatures up to four degrees compared to unirrigated farms or forests. In all, irrigated farms experienced a three- to seven-degree smaller range in daily temperatures compared to other land uses. These effects persisted throughout the year.

A map of the Central Sands region of Wisconsin where researchers studied the effects of irrigation on the local climate. A sensor was placed at each pink dot to mark a line across the region as it changed from pine plantations to farms to forests. Image courtesy Mallika Nocco/Christopher Kucharik

The results show that the conversion of land to irrigated agriculture can have a significant effect on the regional climate, which in turn can affect plant growth, pest pressure and human health in ways that could be overlooked unless land uses are accounted for in forecasts and planning.

Such a cooling effect mitigates — and obscures — a global warming trend induced by the accumulation of greenhouses gases in the atmosphere. Irrigated farming, like all agriculture, also generates greenhouses gases.

The work was led by Mallika Nocco, who recently completed her doctorate in the Nelson Institute for Environmental Studies at the University of Wisconsin–Madison. Nocco worked with Christopher Kucharik of the Nelson Institute and the UW–Madison agronomy department and Robert Smail from the Wisconsin Department of Natural Resources.

The team published their findings July 2 in the journal Global Change Biology.

“We’re finding that weather forecasts can be wrong if they don’t take these land uses into account,” says Nocco, now a postdoctoral researcher at the University of Minnesota. “That will affect both farmers and plants.”

Irrigation, and agriculture generally, cools the air due to the evaporation of water through crop leaves, much like how evaporating sweat cools people. This evaporation also increases the water content of the air. The scientists wanted to determine if the naturally humid Wisconsin climate would respond as strongly to irrigation as drier regions, such as California, do.

To find out, Nocco worked with private landowners to install 28 temperature and humidity sensors in a line that crossed through the Central Sands. The 37-mile transect extended from pine plantations in the west, over irrigated farms toward forests in the east. The researchers collected data across 32 months from the beginning of 2014 through the summer of 2016.

Each of the 28 sensors was matched to nearby irrigation levels through a regional well withdrawal database managed by Smail of the Department of Natural Resources.

Nocco’s team found that irrigation lowered the maximum daily temperature about three and half degrees compared to nearby rainfed farms. Adjacent forests were slightly warmer than either rainfed or irrigated farms.

Somewhat surprisingly, the lower maximum temperatures on irrigated farms were accompanied by higher minimum temperatures. Saturated soils can hold more heat than dry soils. When that heat is released at night, it keeps nighttime minimum temperatures somewhat higher. Wet soils may also be darker, helping them absorb more sunlight during the day.

The researchers found that if all land in the study area were converted to irrigated agriculture, the daily range in temperatures would shrink nearly five degrees Fahrenheit on average, and up to eight degrees at the high end. This smaller difference between daily maximum and minimum temperatures can significantly affect plant growth or insect pest lifecycles, both of which are sensitive to daily temperatures.

“If you’re adjusting the range of temperatures, you’re changing who or what can live in an area,” says Nocco.

The temperature differences between irrigated fields and rain-fed fields or forests were pronounced during the growing season, when fields were being irrigated, but extended throughout the year. Open fields of snow reflect more winter sunlight than forests do, keeping the air above cooler, but it’s not entirely clear what drives winter temperature differences between irrigated and non-irrigated farms.

While the cooling effect of irrigation mitigates global climate change on the regional scale, climate models suggest that regional warming attributed to the global trend will eventually overcome the magnitude of mitigation offered by irrigated agriculture. Farmers, who are partially buffered for now from more extreme heat, would quickly face increasing stress in that scenario.

“Farmers in irrigated regions may experience more abrupt temperature increases that will cause them to have to adapt more quickly than other groups who are already coping with a warming climate,” says Kucharik. “It’s that timeframe in which people have time to adapt that concerns me.”

The current study is the first to definitively link irrigation in the Midwest U.S. to an altered regional climate. These results could improve weather and climate forecasts, help farmers plan better, and, the researchers hope, better prepare agricultural areas to deal with a warming climate when the irrigation effect is washed out.

“Irrigation is a land use with effects on climate in the Midwest, and we need to account for this in our climate models,” says Nocco.

This work was supported in part by the U.S. Environmental Protection Agency, the U.S. Department of Agriculture Sustainable Agriculture Research and Education program and the Wisconsin Department of Natural Resources.

 

 

 

https://www.nature.com/articles/s41467-020-16676-w

The severe drought of the 1930s Dust Bowl decade coincided with record-breaking summer heatwaves that contributed to the socio-economic and ecological disaster over North America’s Great Plains. It remains unresolved to what extent these exceptional heatwaves, hotter than in historically forced coupled climate model simulations, were forced by sea surface temperatures (SSTs) and exacerbated through human-induced deterioration of land cover. Here we show, using an atmospheric-only model, that anomalously warm North Atlantic SSTs enhance heatwave activity through an association with drier spring conditions resulting from weaker moisture transport. Model devegetation simulations, that represent the wide-spread exposure of bare soil in the 1930s, suggest human activity fueled stronger and more frequent heatwaves through greater evaporative drying in the warmer months. This study highlights the potential for the amplification of naturally occurring extreme events like droughts by vegetation feedbacks to create more extreme heatwaves in a warmer world.

 

https://news.ucar.edu/132872/1930s-dust-bowl-affected-extreme-heat-around-northern-hemisphere
 

The 1930s Dust Bowl, fueled by overplowing across the Great Plains and associated with record heat and drought, appears to have affected heat extremes far beyond the United States.

New research finds that the hot, exposed land in the central U.S. during the Dust Bowl drought  influenced temperatures across much of North America and as far away as Europe and East Asia. That’s because the extreme heating of the Great Plains triggered motions of air around the Northern Hemisphere in ways that suppressed cloud formation in some regions and, in combination with the influence of tropical oceanic conditions, led to record heat thousands of miles away.

“The hot and dry conditions over the Great Plains during the Dust Bowl spread extreme heat to other areas of the Northern Hemisphere,” said Gerald Meehl, a scientist with the National Center of Atmospheric Research (NCAR) and lead author of the new study. “If you look at daily record high temperatures, some of these areas are just now breaking the records that were set in the 1930s.”

To determine the climatic impact of the Dust Bowl, the research team drew on observed high and low daily temperatures, as well as advanced computer models of the global climate system. They focused on the role of a teleconnection pattern, known as wave-5, that can regulate the meandering of jet streams and link far-flung weather patterns around the Northern Hemisphere during summer.

The study was published in Scientific Reports. It was funded by the U.S. National Science Foundation, which is NCAR’s sponsor, as well as by the U.S. Department of Energy.

TEASING OUT THE DUST BOWL’S INFLUENCE

The Dust Bowl is widely viewed as one of the nation’s worst environmental disasters. Farmers in the early part of the 20th century plowed up millions of acres of native grassland across much of the Great Plains to plant wheat and other crops. When a multiyear drought struck in the 1930s, the exposed land became exceptionally hot and topsoil blew away, causing devastating dust storms as well as a health and economic catastrophe.

The new research points out that extreme weather conditions extended far beyond the immediate vicinity of the Dust Bowl. Much of North America, northern Europe, and eastern and northeastern Asia experienced such heat that some record high temperatures of the 1930s are only now being exceeded as temperatures rise with climate change.

Previous research pointed to patterns of warm and cool surface temperatures in the tropical oceans as triggering the drought in the Great Plains. These conditions were associated with a pair of multidecadal phenomena known as the Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO). The question addressed by Meehl and his co-authors was whether such oceanic conditions could also explain the hot and dry weather around so much of the Northern Hemisphere, or if the Dust Bowl itself played a role.

To tease out the influence of the Dust Bowl, the scientists first used an NCAR-based model of global climate, known as the Community Earth System Model (CESM). They ran a series of simulations on the Cheyenne supercomputer at the NCAR-Wyoming Supercomputing Center to see whether the IPO and AMO could fully account for the distribution of extreme daily high temperatures across three continents. But even though they set the model to capture the likely oceanic conditions of the time, they could not reproduce the high daily temperatures of the 1930s.

They then turned to a version of the CESM atmospheric model that is a component of the DOE Energy Exascale Earth System Model, and set the model to isolate the influence of the extreme heat over the Great Plains during the 1930s. This time the results closely matched actual climate records, indicating that the Dust Bowl generated an atmospheric reaction that, in combination with conditions in the tropical Pacific and Atlantic, triggered extreme heat across vast areas of the Northern Hemisphere.

“When you put the influence of the Great Plains Dust Bowl drought in the model, you get record-breaking heat in the areas where we saw them in the Northern Hemisphere during the 1930s,” Meehl said.

INFLUENCE OF WAVE-5

Additional analysis of the simulations revealed the reason the Dust Bowl had such a pronounced effect on other regions: it generated a series of far-reaching vertical motions in the atmosphere. Such movements are known as a wavenumber-5 or wave-5 teleconnection — so named because it consists of five pairs of alternating high- and low-pressure features that encircle the globe along jet streams.

In this case, the intense surface heating of the Great Plains created an upward motion of warm air, which then moved downward in surrounding areas, suppressing the formation of clouds over much of the northern U.S. and Canada. It also produced sinking air that suppressed clouds in other regions around the Northern Hemisphere, allowing more sunlight to reach the surface and resulting in soaring temperatures. At the same time, the pattern enabled warm, southerly winds to reach as far north as Scandinavia and eastern Asia. These winds contributed to the extreme heat over much of northern Europe and parts of eastern Asia.

Meehl said the study helps illuminate how conditions on one part of the planet can affect the atmosphere thousands of miles away. Scientists have long known about the climatic influence of the vast tropical oceans, which pump out enormous amounts of relatively moist, warm air affecting weather patterns worldwide, as with El Niño. But it has proven more difficult to tease out linkages that arise from conditions over smaller areas of land in the midlatitudes, especially during summer.

“This is a mechanism that arose in a unique way from human influence — not by burning fossil fuels but from plowing up the middle third of the U.S.,” Meehl said. “It’s possible that intense regional droughts in the future could also influence heat extremes in the Northern Hemisphere.”

 

ABOUT THE ARTICLE

Title: How the Great Plains Dust Bowl drought spread heat extremes around the Northern Hemisphere 
Authors: Gerald A. Meehl, Haiyan Teng, Nan Rosenbloom, Aixue Hu, Claudia Tebaldi, and Guy Walton 
Journal: Scientific Reports

 

[GaWx]

Please comment on the possibility that AGW as well as increased CO2, itself, lead to increased crop sizes due to the possibility of :

-longer growing seasons in existing crop areas due to warming

-areas further north becoming more conducive to growing crops due to warming

-increased CO2 being conducive to larger crops since CO2 leads to increased photosynthesis

 IF these things are true and we're already getting larger crops such as corn due to AGW and increased CO2, how much of that increased corn crop mentioned in the article is actually due to AGW and more CO2, themselves? If true, would that mean a negative feedback from AGW to actually slow the rate of GW? If so, is that negative feedback properly built into the climate model assumptions?

[bluewave]

34 minutes ago, GaWx said:

Please comment on the possibility that AGW as well as increased CO2, itself, lead to increased crop sizes due to the possibility of :

-longer growing seasons in existing crop areas due to warming

-areas further north becoming more conducive to growing crops due to warming

-increased CO2 being conducive to larger crops since CO2 leads to increased photosynthesis

 IF these things are true and we're already getting larger crops such as corn due to AGW and increased CO2, how much of that increased corn crop mentioned in the article is actually due to AGW and more CO2, themselves? If true, would that mean a negative feedback from AGW to actually slow the rate of GW? If so, is that negative feedback properly built into the climate model assumptions?

It appears that the expansion of U.S. agriculture is related to gains in technological advancement. I guess the challenge for the future would be if the Western Drought growth of the last 20 years eventually expands into the Plains like some climate models suggest. The hope is that technology will advance enough to create better heat and drought resistant crops in the future.

 

https://www.usda.gov/media/blog/2020/03/05/look-agricultural-productivity-growth-united-states-1948-2017

[bdgwx]

Here are some of the more recent and relevant publications I have in my stash related to this topic.

Mueller et al. 2016 DOI 10.1038/nclimate2825 – Cooling of US Midwest summer temperature extremes from cropland intensification

Lin et al. 2017 DOI 10.1038/s41467-017-01040-2 – Causes of model dry and warm bias over central U.S. and impact on climate projections

Alter et al. 2018 DOI 10.1002/2017GL075604 – Twentieth Century Regional Climate Change During the Summer in the Central United States Attributed to Agricultural Intensification

Zhang et al. 2018 DOI 10.1002/2017JD027200 – Diagnosis of the Summertime Warm Bias in CMIP5 Climate Models at the ARM Southern Great Plains Site

Qian et al. 2020 DOI 10.1038/s41612-020-00135-w – Neglecting irrigation contributes to the simulated summertime warm-and-dry bias in the central United States

Coffel et al. 2022 DOI 10.1029/2021GL097135 – Earth System Model Overestimation of Cropland Temperatures Scales With Agricultural Intensity

[TheClimateChanger]

19 hours ago, bluewave said:

This is a major reason why the Dust Bowl record highs in this region haven’t been able to be exceeded with global warming causing record highs everywhere else. Our land practices during the Dust Bowl were responsible for greatly amplifying the drought and heat. So the expansion of corn production has created a localized cooling in these areas relative to the rest of the world.
 

https://www.science.org/content/article/america-s-corn-belt-making-its-own-weather

 

The United States’s Corn Belt is making its own weather

By Kimberly HickokFeb. 16, 2018 , 12:05 PM

The Great Plains of the central United States—the Corn Belt—is one of the most fertile regions on Earth, producing more than 10 billion bushels of corn each year. It’s also home to some mysterious weather: Whereas the rest of the world has warmed, the region’s summer temperatures have dropped as much as a full degree Celsius, and rainfall has increased up to 35%, the largest spike anywhere in the world. The culprit, according to a new study, isn’t greenhouse gas emissions or sea surface temperature—it’s the corn itself.

This is the first time anyone has examined regional climate change in the central United States by directly comparing the influence of greenhouse gas emissions to agriculture, says Nathan Mueller, an earth systems scientist at the University of California (UC), Irvine, who was not involved with this study. It’s important to understand howagricultural activity can have “surprisingly strong” impacts on climate change, he says.

The Corn Belt stretches from the panhandle of Texas up to North Dakota and east to Ohio. The amount of corn harvested in this region annually has increased by 400% since 1950, from 2 billion to 10 billion bushels. Iowa leads the country for the most corn produced per state.

To see whether this increase in crops has influenced the region’s unusual weather,researchers at the Massachusetts Institute of Technology in Cambridge used computers to model five different 30-year climate simulations, based on data from 1982 to 2011. First, they compared simulations with high levels of intense agriculture to control simulations with noagricultural influence. Unlike the real-life climate changes, the control simulations showed no change in temperature or rainfall. But 62% of the simulations with intense agriculture resulted in temperature and rainfall changes that mirror the observed changes, the team reports this week in Geophysical Research Letters.

 

Map of the central United States, showing changes in rainfall during the last third of the 20th century. Areas of increased rainfall are shown in green, with darker colors representing a greater increase.

MASSACHUSETTS INSTITUTE OF TECHNOLOGY 

The team then compared its results to historical global simulations from the World Climate Research Programme (WCRP), an international program for the coordination of global climate research sponsored by the International Council for Science, the World Meteorological Organization, and the Intergovernmental Oceanographic Commission of UNESCO. WCRP’s models take into account greenhouse gas emissions and other natural and humanmade influences, but do not consider agricultural land use. When researchers ran the numbers for the Corn Belt, the global models fell short of reality: They predicted both temperature and humidity to increase slightly, and rainfall to increase by up to 4%—none of which matches the observed changes.

Other climate simulations that use sea surface temperature variation didn’t match observed changes, either. Those simulations matchedhistorical data until 1970; after that, the simulations predicted temperatures to keep increasing, rather than decreasing as they did in reality. This is a strong indication that agriculture, and not changing sea surface temperature, caused the regional changes in climate during the last third of the 20th century, the researchers say.

“The [influence] of agriculture intensification is really an independent problem from greenhouse gas emissions,” says Ross Alter, lead author of the study and now a meteorologist with the U.S. Army Corps of Engineers in Hanover, New Hampshire. In fact, Alter says, heavy agriculture likely counteracted rising temperatures regionally that might have otherwise resulted from increasing greenhouse gas emissions. One other place that shows a similar drop in temperatures, he notes, is eastern China, where intensive agriculture is widespread.

But how does agriculture cause increased rainfall and decreased temperatures? The team suspects it has to do with photosynthesis, which leads to more water vapor in the air. When a plant’s pores, called stomata, open to allow carbondioxide to enter, they simultaneously allow water to escape. This increases the amount of water going into the atmosphere and returning as rainfall. The cycle may continue as that rainwater eventually moves back into the atmosphere and causes more rainfall downwind from the original agricultural area.

Rong Fu, a climate scientist at UC Los Angeles, agrees with the team’s assessment. She alsothinks that though human influence might be “greater than we realize,” this regional climate change is probably caused by many factors,including increased irrigation in the region.

“This squares with a lot of other evidence,” says Peter Huybers, a climate scientist at Harvard University, who calls the new study convincing. But he warns that such benefits may not last if greenhouse gas emissions eventually overpower the mitigating effect of agriculture.

Alter agrees, and says it’s unlikely that the large increases in U.S. crop production during the 20th century will continue. Other scientists have voiced concern that agricultural production could soon be reaching its limit in many parts of the world. 

“Food production is arguably what we’re more concerned about with climate change,” Mueller says. And understanding how agriculture and climate will continue to affect one another is crucial for developing projections for both climate and agricultural yields. “It’s not just greenhousegasses that we need to be thinking about.” 


https://news.wisc.edu/irrigated-farming-in-wisconsins-central-sands-cools-the-regions-climate/
 

New research finds that irrigated farms within Wisconsin’s vegetable-growing Central Sands region significantly cool the local climate compared to nearby rain-fed farms or forests.

Irrigation dropped maximum temperatures by one to three degrees Fahrenheit on average while increasing minimum temperatures up to four degrees compared to unirrigated farms or forests. In all, irrigated farms experienced a three- to seven-degree smaller range in daily temperatures compared to other land uses. These effects persisted throughout the year.

A map of the Central Sands region of Wisconsin where researchers studied the effects of irrigation on the local climate. A sensor was placed at each pink dot to mark a line across the region as it changed from pine plantations to farms to forests. Image courtesy Mallika Nocco/Christopher Kucharik

The results show that the conversion of land to irrigated agriculture can have a significant effect on the regional climate, which in turn can affect plant growth, pest pressure and human health in ways that could be overlooked unless land uses are accounted for in forecasts and planning.

Such a cooling effect mitigates — and obscures — a global warming trend induced by the accumulation of greenhouses gases in the atmosphere. Irrigated farming, like all agriculture, also generates greenhouses gases.

The work was led by Mallika Nocco, who recently completed her doctorate in the Nelson Institute for Environmental Studies at the University of Wisconsin–Madison. Nocco worked with Christopher Kucharik of the Nelson Institute and the UW–Madison agronomy department and Robert Smail from the Wisconsin Department of Natural Resources.

The team published their findings July 2 in the journal Global Change Biology.

“We’re finding that weather forecasts can be wrong if they don’t take these land uses into account,” says Nocco, now a postdoctoral researcher at the University of Minnesota. “That will affect both farmers and plants.”

Irrigation, and agriculture generally, cools the air due to the evaporation of water through crop leaves, much like how evaporating sweat cools people. This evaporation also increases the water content of the air. The scientists wanted to determine if the naturally humid Wisconsin climate would respond as strongly to irrigation as drier regions, such as California, do.

To find out, Nocco worked with private landowners to install 28 temperature and humidity sensors in a line that crossed through the Central Sands. The 37-mile transect extended from pine plantations in the west, over irrigated farms toward forests in the east. The researchers collected data across 32 months from the beginning of 2014 through the summer of 2016.

Each of the 28 sensors was matched to nearby irrigation levels through a regional well withdrawal database managed by Smail of the Department of Natural Resources.

Nocco’s team found that irrigation lowered the maximum daily temperature about three and half degrees compared to nearby rainfed farms. Adjacent forests were slightly warmer than either rainfed or irrigated farms.

Somewhat surprisingly, the lower maximum temperatures on irrigated farms were accompanied by higher minimum temperatures. Saturated soils can hold more heat than dry soils. When that heat is released at night, it keeps nighttime minimum temperatures somewhat higher. Wet soils may also be darker, helping them absorb more sunlight during the day.

The researchers found that if all land in the study area were converted to irrigated agriculture, the daily range in temperatures would shrink nearly five degrees Fahrenheit on average, and up to eight degrees at the high end. This smaller difference between daily maximum and minimum temperatures can significantly affect plant growth or insect pest lifecycles, both of which are sensitive to daily temperatures.

“If you’re adjusting the range of temperatures, you’re changing who or what can live in an area,” says Nocco.

The temperature differences between irrigated fields and rain-fed fields or forests were pronounced during the growing season, when fields were being irrigated, but extended throughout the year. Open fields of snow reflect more winter sunlight than forests do, keeping the air above cooler, but it’s not entirely clear what drives winter temperature differences between irrigated and non-irrigated farms.

While the cooling effect of irrigation mitigates global climate change on the regional scale, climate models suggest that regional warming attributed to the global trend will eventually overcome the magnitude of mitigation offered by irrigated agriculture. Farmers, who are partially buffered for now from more extreme heat, would quickly face increasing stress in that scenario.

“Farmers in irrigated regions may experience more abrupt temperature increases that will cause them to have to adapt more quickly than other groups who are already coping with a warming climate,” says Kucharik. “It’s that timeframe in which people have time to adapt that concerns me.”

The current study is the first to definitively link irrigation in the Midwest U.S. to an altered regional climate. These results could improve weather and climate forecasts, help farmers plan better, and, the researchers hope, better prepare agricultural areas to deal with a warming climate when the irrigation effect is washed out.

“Irrigation is a land use with effects on climate in the Midwest, and we need to account for this in our climate models,” says Nocco.

This work was supported in part by the U.S. Environmental Protection Agency, the U.S. Department of Agriculture Sustainable Agriculture Research and Education program and the Wisconsin Department of Natural Resources.

 

 

 

https://www.nature.com/articles/s41467-020-16676-w

The severe drought of the 1930s Dust Bowl decade coincided with record-breaking summer heatwaves that contributed to the socio-economic and ecological disaster over North America’s Great Plains. It remains unresolved to what extent these exceptional heatwaves, hotter than in historically forced coupled climate model simulations, were forced by sea surface temperatures (SSTs) and exacerbated through human-induced deterioration of land cover. Here we show, using an atmospheric-only model, that anomalously warm North Atlantic SSTs enhance heatwave activity through an association with drier spring conditions resulting from weaker moisture transport. Model devegetation simulations, that represent the wide-spread exposure of bare soil in the 1930s, suggest human activity fueled stronger and more frequent heatwaves through greater evaporative drying in the warmer months. This study highlights the potential for the amplification of naturally occurring extreme events like droughts by vegetation feedbacks to create more extreme heatwaves in a warmer world.

 

https://news.ucar.edu/132872/1930s-dust-bowl-affected-extreme-heat-around-northern-hemisphere
 

The 1930s Dust Bowl, fueled by overplowing across the Great Plains and associated with record heat and drought, appears to have affected heat extremes far beyond the United States.

New research finds that the hot, exposed land in the central U.S. during the Dust Bowl drought  influenced temperatures across much of North America and as far away as Europe and East Asia. That’s because the extreme heating of the Great Plains triggered motions of air around the Northern Hemisphere in ways that suppressed cloud formation in some regions and, in combination with the influence of tropical oceanic conditions, led to record heat thousands of miles away.

“The hot and dry conditions over the Great Plains during the Dust Bowl spread extreme heat to other areas of the Northern Hemisphere,” said Gerald Meehl, a scientist with the National Center of Atmospheric Research (NCAR) and lead author of the new study. “If you look at daily record high temperatures, some of these areas are just now breaking the records that were set in the 1930s.”

To determine the climatic impact of the Dust Bowl, the research team drew on observed high and low daily temperatures, as well as advanced computer models of the global climate system. They focused on the role of a teleconnection pattern, known as wave-5, that can regulate the meandering of jet streams and link far-flung weather patterns around the Northern Hemisphere during summer.

The study was published in Scientific Reports. It was funded by the U.S. National Science Foundation, which is NCAR’s sponsor, as well as by the U.S. Department of Energy.

TEASING OUT THE DUST BOWL’S INFLUENCE

The Dust Bowl is widely viewed as one of the nation’s worst environmental disasters. Farmers in the early part of the 20th century plowed up millions of acres of native grassland across much of the Great Plains to plant wheat and other crops. When a multiyear drought struck in the 1930s, the exposed land became exceptionally hot and topsoil blew away, causing devastating dust storms as well as a health and economic catastrophe.

The new research points out that extreme weather conditions extended far beyond the immediate vicinity of the Dust Bowl. Much of North America, northern Europe, and eastern and northeastern Asia experienced such heat that some record high temperatures of the 1930s are only now being exceeded as temperatures rise with climate change.

Previous research pointed to patterns of warm and cool surface temperatures in the tropical oceans as triggering the drought in the Great Plains. These conditions were associated with a pair of multidecadal phenomena known as the Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO). The question addressed by Meehl and his co-authors was whether such oceanic conditions could also explain the hot and dry weather around so much of the Northern Hemisphere, or if the Dust Bowl itself played a role.

To tease out the influence of the Dust Bowl, the scientists first used an NCAR-based model of global climate, known as the Community Earth System Model (CESM). They ran a series of simulations on the Cheyenne supercomputer at the NCAR-Wyoming Supercomputing Center to see whether the IPO and AMO could fully account for the distribution of extreme daily high temperatures across three continents. But even though they set the model to capture the likely oceanic conditions of the time, they could not reproduce the high daily temperatures of the 1930s.

They then turned to a version of the CESM atmospheric model that is a component of the DOE Energy Exascale Earth System Model, and set the model to isolate the influence of the extreme heat over the Great Plains during the 1930s. This time the results closely matched actual climate records, indicating that the Dust Bowl generated an atmospheric reaction that, in combination with conditions in the tropical Pacific and Atlantic, triggered extreme heat across vast areas of the Northern Hemisphere.

“When you put the influence of the Great Plains Dust Bowl drought in the model, you get record-breaking heat in the areas where we saw them in the Northern Hemisphere during the 1930s,” Meehl said.

INFLUENCE OF WAVE-5

Additional analysis of the simulations revealed the reason the Dust Bowl had such a pronounced effect on other regions: it generated a series of far-reaching vertical motions in the atmosphere. Such movements are known as a wavenumber-5 or wave-5 teleconnection — so named because it consists of five pairs of alternating high- and low-pressure features that encircle the globe along jet streams.

In this case, the intense surface heating of the Great Plains created an upward motion of warm air, which then moved downward in surrounding areas, suppressing the formation of clouds over much of the northern U.S. and Canada. It also produced sinking air that suppressed clouds in other regions around the Northern Hemisphere, allowing more sunlight to reach the surface and resulting in soaring temperatures. At the same time, the pattern enabled warm, southerly winds to reach as far north as Scandinavia and eastern Asia. These winds contributed to the extreme heat over much of northern Europe and parts of eastern Asia.

Meehl said the study helps illuminate how conditions on one part of the planet can affect the atmosphere thousands of miles away. Scientists have long known about the climatic influence of the vast tropical oceans, which pump out enormous amounts of relatively moist, warm air affecting weather patterns worldwide, as with El Niño. But it has proven more difficult to tease out linkages that arise from conditions over smaller areas of land in the midlatitudes, especially during summer.

“This is a mechanism that arose in a unique way from human influence — not by burning fossil fuels but from plowing up the middle third of the U.S.,” Meehl said. “It’s possible that intense regional droughts in the future could also influence heat extremes in the Northern Hemisphere.”

 

ABOUT THE ARTICLE

Title: How the Great Plains Dust Bowl drought spread heat extremes around the Northern Hemisphere 
Authors: Gerald A. Meehl, Haiyan Teng, Nan Rosenbloom, Aixue Hu, Claudia Tebaldi, and Guy Walton 
Journal: Scientific Reports

 

No reason to expect this to continue for the rest of this century or beyond. I would expect to eventually reach a level of warming where it is no longer feasible to grow most crops in that region, which would lead to crop failures and extremely rapid warming. In such a scenario, the cooling effect would not only be reversed, but replaced by an articifial warming effect of a desert-like landscape devoid of crops. If this were to occur, parts of the midwest could see temperatures approach or exceed the all-time world record. Temperatures of 120+ have already been observed in the Dakotas, including at CO2 levels not much above 300 ppm. I don't think it's out of the question to see 130+, maybe even 140 degrees, were that same weather pattern to recur at CO2 levels of say 450-500 ppm. Even if high temperatures stay in the 110s to around 120, low temperatures may struggle to drop below 95 or 100 in the high CO2 environment. This type of warmth would dessicate and destroy all plant life in the region, leading to flash desertification.

I don't know if this is an effect the models produce. But this is just thinking logically and using past weather as a guide to project what could happen in a worst-case scenario. Unfortunately, most people seem unwilling to even consider the possibility of a worst-case scenario. And instead point to the 1934 and 1936 drought and heat wave as evidence of past periods of climate tumult and assume (incorrectly) that our improved farming and soil conservation techniques will prevent that from recurring. However, it is certainly possible that the weather, in the near future, could become so harsh that there is a season where widespread crop failures occur despite our agricultural advances. If this were to occur, then you could see a recurrence of Dust Bowl conditions in a high CO2, enhanced greenhouse effect environment.

[bluewave]

Similar cooler pattern this July in the Plains like the longer term warm season trend has shown. It would make an interesting study to see if the increased agriculture and irrigation is affecting  the Rossby wave train in some way. A study has shown that the Dust Bowl heating from the poor land use practices actually altered the Northern Hemisphere summer circulation. 
 

Time Series Summary for Rapid City Area, SD (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Rank	Ending Date	Mean Avg Temperature Jul 1 to Jul 25	Missing Count
1	1992-07-25	63.7	0
2	1993-07-25	64.2	0
3	1972-07-25	64.4	0
4	1950-07-25	66.2	0
5	1958-07-25	67.0	0
6	1944-07-25	68.2	0
7	2009-07-25	68.7	0
-	1951-07-25	68.7	0
8	2010-07-25	69.1	0
9	2023-07-25	69.3	0
10	1968-07-25	69.5	0

[TheClimateChanger]

Looks like there is a pretty strong relationship between El Nino conditions and cool Julys at Rapid City. Not sure about the corn effect though. Looks like the coldest anomalies are west of the Corn Belt this year. In fact, I don't think Rapid City or surroundings have a significant cropland presence for that matter.

Edit: Also suspect the omnipresent Canadian wildfire smoke and haze has assisted in the cool anomalies across the northern Plains this summer by filtering the sunlight. While we have had some outbreaks of smoke in the Great Lakes and northeast, the northern Plains has been ground zero for a lot of the smoke.

[TheClimateChanger]

Also, I would expect Rapid City's ranking to climb well out of the top ten with the ongoing heat wave. Already up to 88 as of 9:50-ish a.m. local time. Looks like it may reach 100 there today.

And upon further review, looks like Rapid City's warmest Julys are dominated by years in the past couple of decades. So not much evidence of a cooling trend.

[bluewave]

24 minutes ago, TheClimateChanger said:

Looks like there is a pretty strong relationship between El Nino conditions and cool Julys at Rapid City. Not sure about the corn effect though. Looks like the coldest anomalies are west of the Corn Belt this year. In fact, I don't think Rapid City or surroundings have a significant cropland presence for that matter.

Edit: Also suspect the omnipresent Canadian wildfire smoke and haze has assisted in the cool anomalies across the northern Plains this summer by filtering the sunlight.

The corn belt is located more over Eastern SD. But I just bring up to add as one factor out of several including ENSO teleconnections. There are several layers to a hemispheric Rossby wave pattern. Whether the Corn Belt cooler and wetter influence is working to alter the background Rossby wave pattern is still an unknown. We have several examples when the  influence is warmer instead of cooler. It could also be working on a level to cool further what would have already been a cooler El Niño teleconnection pattern for the Plains. So would need a model study to isolate possible influences in the overall upper pattern. In any event, those extreme dust bowl heat records should be safe for another July.

 

 

[TheClimateChanger]

2 hours ago, bluewave said:

The corn belt is located more over Eastern SD. But I just bring up to add as one factor out of several including ENSO teleconnections. There are several layers to a hemispheric Rossby wave pattern. Whether the Corn Belt cooler and wetter influence is working to alter the background Rossby wave pattern is still an unknown. We have several examples when the  influence is warmer instead of cooler. It could also be working on a level to cool further what would have already been a cooler El Niño teleconnection pattern for the Plains. So would need a model study to isolate possible influences in the overall upper pattern. In any event, those extreme dust bowl heat records should be safe for another July.

 

 

It looks like coastal regions in general are warming faster than continental interiors, with extreme marine heatwaves present near multiple coastlines driving intense surface air warming. Perhaps the models are simply incorrect, and coastal regions experience more warming from an enhanced greenhouse than do continental interiors? You can even see that same effect in the Alaskan inset, with a relative minimum of warming in the Alaskan interior and enhanced warming along all of the coastlines.

[bdgwx]

20 hours ago, TheClimateChanger said:

Perhaps the models are simply incorrect, and coastal regions experience more warming from an enhanced greenhouse than do continental interiors?

Refer to my post above. The issue is land use changes in the interior specifically in the corn belt as a result of agricultural intensification. This attenuates the warming in that region. The issue with modeling is two fold: 1) they have inadequate parameterization schemes to fully capture how the land use changes effect the climate in this region and 2) they have inadequate inputs on the land use changes themselves (eg. neglecting irrigation).

[forkyfork]

would there be a cooling trend if we plotted theta e instead of temperature?

[csnavywx]

14 minutes ago, forkyfork said:

would there be a cooling trend if we plotted theta e instead of temperature?

Nope. Well documented increase in mixing ratios/dews to go along with that trend.

It's a transient response almost by default since planting density is already very high and most of the land that can be farmed already is. Crank it a few more degrees and you set up a pretty vicious snap-back temp response once crops start having heat issues and the ET response is weakened.

[bluewave]

The cooling effect from the expansion of agriculture and irrigation is most pronounced in the long term decline in very hot 95° and higher days across the region.

 

https://cbs2iowa.com/news/local/special-report-iowas-changing-climate

Higher humidity also has impact on temperatures during every season. In summer, average days above 95 degrees in Cedar Rapids from 1894 through 2018 fell by 12.7 days.

“We don't seem to have the heat that we used to have when I started back in the 80s and the 70s,” said Weather First Chief Meteorologist Terry Swails. “A lot of temperatures, 98 to 102, that seemed like it was pretty common. It was rare if we went a summer without at least one 100-degree day. Now that's a rare event. It seems if we get 95 that's kind of a big deal.”

 

 

[Bhs1975]

So if we drastically lowered emissions and irrigated and grew plants on as much available land as possible it would both provide a cooling effect and draw down huge amounts of CO2.

[csnavywx]

1 minute ago, Bhs1975 said:

So if we drastically lowered emissions and irrigated and grew plants on as much available land as possible it would both provide a cooling effect and draw down huge amounts of CO2.

The "price" is higher dewpoints. CO2 drawdown isn't really a thing beyond the delta you'd get by increasing planting density, which is already very high. Converting it all back to forest would work to a degree, but we aren't going to do that.

[TheClimateChanger]

10 minutes ago, Bhs1975 said:

So if we drastically lowered emissions and irrigated and grew plants on as much available land as possible it would both provide a cooling effect and draw down huge amounts of CO2.

No, because what these reports never tell you is the concomitant increase in dewpoints from the anthropogenically enhanced transpiration. Peoria, Illinois, for instance, had a heat index of 104F at 1 am. Some of these areas will likely see wet bulb temperatures approach the theoretical limits of human survivability later this century. Not to mention the devestation wrought on native plants and animals, which have evolved to live in a drier climate with periodic heat extremes.

[TheClimateChanger]

4 minutes ago, csnavywx said:

The "price" is higher dewpoints. CO2 drawdown isn't really a thing beyond the delta you'd get by increasing planting density, which is already very high. Converting it all back to forest would work to a degree, but we aren't going to do that.

Most of the region was prairie, not forest. You can't convert it back to something it never was.

[TheClimateChanger]

The use of data from Cedar Rapids also makes the trend look more pronounced. Cedar Rapids is often one of the cooler spots in the state of Iowa. The early records have an unbelievable number of days of 95+.  It's not believable that Cedar Rapids would have experienced more days of 95+ than Des Moines in those years. That makes no sense climatologically.

The data for Des Moines also show a trend towards less, but not nearly that pronounced.

 

 

[bluewave]

2 hours ago, TheClimateChanger said:

The use of data from Cedar Rapids also makes the trend look more pronounced. Cedar Rapids is often one of the cooler spots in the state of Iowa. The early records have an unbelievable number of days of 95+.  It's not believable that Cedar Rapids would have experienced more days of 95+ than Des Moines in those years. That makes no sense climatologically.

The data for Des Moines also show a trend towards less, but not nearly that pronounced.

 

 

 

Cedar Rapids is located in a zone of dense agriculture so the effect is well known by the locals. There is nothing wrong with the charts. Ames Iowa shows a similar steep decline since the late 1800s. You can also look at the decrease across the entire state. Des Moines also has a higher population and has a larger urbanized footprint than Cedar Rapids.

 

https://cbs2iowa.com/news/local/special-report-iowas-changing-climate

Higher humidity also has impact on temperatures during every season. In summer, average days above 95 degrees in Cedar Rapids from 1894 through 2018 fell by 12.7 days.

“We don't seem to have the heat that we used to have when I started back in the 80s and the 70s,” said Weather First Chief Meteorologist Terry Swails. “A lot of temperatures, 98 to 102, that seemed like it was pretty common. It was rare if we went a summer without at least one 100-degree day. Now that's a rare event. It seems if we get 95 that's kind of a big 

Trend in days above 95 degrees has seen a steep decrease since the late 1800s.

Statewide decrease in 95° very hot days.

 

https://statesummaries.ncics.org/chapter/ia/

[TheClimateChanger]

@bluewave

I bet dewpoint and apparent temperatures are rising though.

Here are three plots for Des Moines (1936-present). Starting in the hottest month on record also probably effects this trend. Take particular notice of the trend in dew points. Surprisingly, despite the major heat, 1936 had the lowest mean dewpoint of record for any year from 1936 to the present. Thus, despite the temperature that month being 1.5F warmer than the second warmest year on record (2012), both 2012 & 2011 had higher mean apparent temperatures. There's two recent summers that "felt" hotter than 1936, even if the official numbers say they were cooler. Not enough emphasis is placed on the increased humidity that has also occurred. Just in the past 13 years, there have been two Julys that have presented Iowans with a more brutal combination of heat & humidity than July 1936, but you won't hear about it because the only thing ever reported is the dry bulb temperature.

Actually, 2011 (which is only 5th warmest on record by mean temperature) has the highest mean apparent temperature of record. No data for 1901 or 1934, although given the drought conditions would expect them to have mean apparent temperatures that don't deviate significantly from the actual temperature.

Temperature [+1.18F/century]

Dew Point [+3.18F/century]

Heat Index [+2.07F/century]

 

[TheClimateChanger]

On 7/28/2023 at 11:28 AM, bluewave said:

Cedar Rapids is located in a zone of dense agriculture so the effect is well known by the locals. There is nothing wrong with the charts. Ames Iowa shows a similar steep decline since the late 1800s. You can also look at the decrease across the entire state. Des Moines also has a higher population and has a larger urbanized footprint than Cedar Rapids.

Not be to be argumentative, we are on the same side here. But also keep in mind changes in observation time and site location. That chart is based on raw data from a threaded record.

Observations moved to the airport in 1953, which is right around the time that graph shows a huge dropoff in 95+ days at Cedar Rapids.

More importantly, the airport data is likely midnight to midnight. The min & max thermometers from the co-op data were likely reset in the late afternoon or early evening, as was common practice at the time. This is colloquially known as the TOBS error, or time of observation bias.

It can significantly impact analyses of maximum temperatures, especially when looking at days above a certain threshold. Due to the time of observation, an extra hot day appears in the records after each hot period. Because if the high was 97F, the temperature at 5 or 6 pm would probably still be 93-95F, and then that's what the max thermometer is reset to read. The high the next day might only be 87F, but the high would be recorded as 95F. This can add a not insignificant number of hot days to the record, if left uncorrected.

I'm not saying the number of very hot days isn't down somewhat, but I believe that graphic is exaggerated for these reasons.

[GaWx]

4 hours ago, TheClimateChanger said:

@bluewave

I bet dewpoint and apparent temperatures are rising though.

Here are three plots for Des Moines (1936-present). Starting in the hottest month on record also probably effects this trend. Take particular notice of the trend in dew points. Surprisingly, despite the major heat, 1936 had the lowest mean dewpoint of record for any year from 1936 to the present. Thus, despite the temperature that month being 1.5F warmer than the second warmest year on record (2012), both 2012 & 2011 had higher mean apparent temperatures. There's two recent summers that "felt" hotter than 1936, even if the official numbers say they were cooler. Not enough emphasis is placed on the increased humidity that has also occurred. Just in the past 13 years, there have been two Julys that have presented Iowans with a more brutal combination of heat & humidity than July 1936, but you won't hear about it because the only thing ever reported is the dry bulb temperature.

Actually, 2011 (which is only 5th warmest on record by mean temperature) has the highest mean apparent temperature of record. No data for 1901 or 1934, although given the drought conditions would expect them to have mean apparent temperatures that don't deviate significantly from the actual temperature.

Temperature [+1.18F/century]

Dew Point [+3.18F/century]

Heat Index [+2.07F/century]

 

1. It isn't surprising to me that 1936 had the lowest dewpoints at Des Moines as that was during the heart of the Dust Bowl years and that July had the 3rd lowest rainfall of any during 1936-2023. The 1936 IA corn crop of 189 million bushels was by a good margin the smallest during 1936-2023 (see link). Decreased vegetation correlates well with not only hotter summer temperatures but also lower dewpoints (less evapotranspiration). The record heat and low dewpoints are naturally associated.

IA Corn crop by year:

https://beef2live.com/story-iowa-corn-production-year-85-205696

 

2. I've read a lot about the correlation between GW/CC and increased droughts. But related to GW/CC, dewpoints have increased significantly in recent decades in many places along with temperatures. I know they have here in the SE US, especially in summer. With that being the case, have relative humidities actually remained about the same? I'm asking this because the idea of increased droughts is as I understand it partially based on lower RHs due to hotter temperatures. But have RHs actually been dropping?

[bluewave]

 

[Blizzard92]

While land surface feedbacks are certainly playing a role, we recently reinvestigated this issue and found that ocean-atmosphere interactions can also force this area of cooling:

Eischeid, J.K., M.P. Hoerling, X.-W. Quan, A. Kumar, J. Barsugli, Z.M. Labe, K.E. Kunkel, C.J. Schreck III, D.R. Easterling, T. Zhang, J. Uehling, and X. Zhang (2023). Why has the summertime central U.S. warming hole not disappeared? Journal of Climate, DOI:10.1175/JCLI-D-22-0716.1 https://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-22-0716.1/JCLI-D-22-0716.1.xml

[TheClimateChanger]

21 hours ago, bluewave said:

 

I just don't buy it. The missing warming just seems to be bad data. The official NWS stations show plenty of warming.

Omaha, NE

Relative to 1961-1990, the last 14 years at Omaha have averaged 2.9F warmer in June, 1.2F warmer in July, and 1.8F warmer in August. 

 

[TheClimateChanger]

Des Moines, IA

Relative to 1961-1990, the last 14 years at Des Moines have averaged 2.8F warmer in June, 1.2F warmer in July, and 1.7F warmer in August [+2.9, +1.6, +1.7, respectively, compared to 1951-1980].

[TheClimateChanger]

The alleged cool zone doesn't withstand scrutiny. It's warming rapidly in those areas in the summertime at official, first order NWS observation sites.

[bluewave]

1 hour ago, TheClimateChanger said:

I just don't buy it. The missing warming just seems to be bad data. The official NWS stations show plenty of warming.

Omaha, NE

Relative to 1961-1990, the last 14 years at Omaha have averaged 2.9F warmer in June, 1.2F warmer in July, and 1.8F warmer in August. 

 

What isn’t to buy? Omaha has had unchanged summer high temperatures since the rapid expansion of corn production from 1961-1990 to 1991-2020 at 85.3. Remember that is only one point the map. Numerous higher order sites in the NCDC network have actually seen a small drop in temperature. Any increase in average temperatures is a result of rising minimums which is due to the corn producing higher dew points.
 

Monthly Mean Max Temperature for Omaha Area, NE (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Year	Jun	Jul	Aug	Season
Mean	83.7	87.3	85.0	85.3
2020	89.2	89.6	88.6	89.1
2019	83.5	87.3	83.7	84.8
2018	87.6	87.5	86.0	87.0
2017	88.2	90.5	83.1	87.3
2016	90.6	87.1	85.9	87.9
2015	83.4	86.9	82.9	84.4
2014	83.4	84.3	83.8	83.8
2013	81.6	86.9	87.2	85.2
2012	87.1	96.9	88.2	90.7
2011	82.5	90.1	84.9	85.8
2010	84.4	87.3	89.2	87.0
2009	81.6	81.7	81.9	81.7
2008	82.3	87.2	87.6	85.7
2007	83.7	89.6	87.7	87.0
2006	86.9	91.5	83.9	87.4
2005	85.9	90.9	85.5	87.4
2004	78.8	82.1	80.3	80.4
2003	79.7	89.5	89.7	86.3
2002	88.4	91.5	85.2	88.4
2001	82.2	88.5	86.8	85.8
2000	82.0	84.0	87.0	84.3
1999	80.2	90.4	82.8	84.5
1998	79.4	85.5	84.9	83.3
1997	85.7	87.3	83.2	85.4
1996	83.7	82.9	82.2	82.9
1995	82.4	91.9	90.2	88.2
1994	84.0	84.2	84.0	84.1
1993	78.5	81.5	82.7	80.9
1992	79.3	78.5	77.9	78.6
1991	83.7	85.4	84.2	84.4

 

Monthly Mean Max Temperature for Omaha Area, NE (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Year	Jun	Jul	Aug	Season
Mean	83.4	87.6	84.9	85.3
1990	83.3	83.7	84.9	84.0
1989	80.2	87.0	84.5	83.9
1988	88.2	86.3	88.8	87.8
1987	85.2	88.9	79.6	84.6
1986	84.4	87.1	78.7	83.4
1985	79.1	85.8	80.0	81.6
1984	81.7	86.8	88.2	85.6
1983	79.4	89.8	92.0	87.1
1982	76.2	86.5	80.3	81.0
1981	84.9	85.7	80.5	83.7
1980	82.9	89.7	86.2	86.3
1979	81.9	82.8	83.6	82.8
1978	83.2	84.6	84.5	84.1
1977	83.6	89.7	80.4	84.6
1976	86.4	90.9	90.1	89.1
1975	83.9	92.1	92.0	89.3
1974	83.7	97.1	82.0	87.6
1973	86.2	85.6	89.2	87.0
1972	85.2	84.0	83.8	84.3
1971	89.7	85.6	86.7	87.3
1970	86.0	89.3	87.8	87.7
1969	79.0	87.5	86.2	84.2
1968	86.0	87.3	85.0	86.1
1967	80.8	86.2	84.0	83.7
1966	83.2	88.9	82.3	84.8
1965	81.7	85.3	86.1	84.4
1964	83.0	91.0	82.0	85.3
1963	86.8	88.8	85.0	86.9
1962	82.3	85.6	85.9	84.6
1961	82.7	87.5	85.5	85.2

[TheClimateChanger]

25 minutes ago, bluewave said:

What isn’t to buy? Omaha has had unchanged summer high temperatures since the rapid expansion of corn production from 1961-1990 to 1991-2020 at 85.3. Remember that is only one point the map. Numerous higher order sites in the NCDC network have actually seen a small drop in temperature. Any increase in average temperatures is a result of rising minimums which is due to the corn producing higher dew points.
 

Monthly Mean Max Temperature for Omaha Area, NE (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Year	Jun	Jul	Aug	Season
Mean	83.7	87.3	85.0	85.3
2020	89.2	89.6	88.6	89.1
2019	83.5	87.3	83.7	84.8
2018	87.6	87.5	86.0	87.0
2017	88.2	90.5	83.1	87.3
2016	90.6	87.1	85.9	87.9
2015	83.4	86.9	82.9	84.4
2014	83.4	84.3	83.8	83.8
2013	81.6	86.9	87.2	85.2
2012	87.1	96.9	88.2	90.7
2011	82.5	90.1	84.9	85.8
2010	84.4	87.3	89.2	87.0
2009	81.6	81.7	81.9	81.7
2008	82.3	87.2	87.6	85.7
2007	83.7	89.6	87.7	87.0
2006	86.9	91.5	83.9	87.4
2005	85.9	90.9	85.5	87.4
2004	78.8	82.1	80.3	80.4
2003	79.7	89.5	89.7	86.3
2002	88.4	91.5	85.2	88.4
2001	82.2	88.5	86.8	85.8
2000	82.0	84.0	87.0	84.3
1999	80.2	90.4	82.8	84.5
1998	79.4	85.5	84.9	83.3
1997	85.7	87.3	83.2	85.4
1996	83.7	82.9	82.2	82.9
1995	82.4	91.9	90.2	88.2
1994	84.0	84.2	84.0	84.1
1993	78.5	81.5	82.7	80.9
1992	79.3	78.5	77.9	78.6
1991	83.7	85.4	84.2	84.4

 

Monthly Mean Max Temperature for Omaha Area, NE (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Year	Jun	Jul	Aug	Season
Mean	83.4	87.6	84.9	85.3
1990	83.3	83.7	84.9	84.0
1989	80.2	87.0	84.5	83.9
1988	88.2	86.3	88.8	87.8
1987	85.2	88.9	79.6	84.6
1986	84.4	87.1	78.7	83.4
1985	79.1	85.8	80.0	81.6
1984	81.7	86.8	88.2	85.6
1983	79.4	89.8	92.0	87.1
1982	76.2	86.5	80.3	81.0
1981	84.9	85.7	80.5	83.7
1980	82.9	89.7	86.2	86.3
1979	81.9	82.8	83.6	82.8
1978	83.2	84.6	84.5	84.1
1977	83.6	89.7	80.4	84.6
1976	86.4	90.9	90.1	89.1
1975	83.9	92.1	92.0	89.3
1974	83.7	97.1	82.0	87.6
1973	86.2	85.6	89.2	87.0
1972	85.2	84.0	83.8	84.3
1971	89.7	85.6	86.7	87.3
1970	86.0	89.3	87.8	87.7
1969	79.0	87.5	86.2	84.2
1968	86.0	87.3	85.0	86.1
1967	80.8	86.2	84.0	83.7
1966	83.2	88.9	82.3	84.8
1965	81.7	85.3	86.1	84.4
1964	83.0	91.0	82.0	85.3
1963	86.8	88.8	85.0	86.9
1962	82.3	85.6	85.9	84.6
1961	82.7	87.5	85.5	85.2

The map posted by Brian Brettschneider is mean temperature, not average maximum. Both Des Moines and Omaha have very closely aligned trends and have warmed around 2F in the summertime just over the past couple of decades. The map shows little to no trend in that region. Given the trends match almost exactly, it would appear to be a regionwide warming and not something specific to either site. These are first-order stations that have been in the same location for decades, in two quiet cities that haven't experienced any population growth or significant increase in urbanization since the late 20th century, ruling out the possibility of urban heating effects.

Maybe there's no trend if you are taking temperature in the middle of a cornfield, but that's not how the temperature is supposed to be recorded. Could be impacts from shading or improper exposure, similar to New York City's Central Park, which shows smaller warming trends than surrounding areas?