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

[TheClimateChanger]

Also, when I look at the most recent 14 years (2010-2023), I find a significant warming trend in daily maximum temperatures at Omaha - particularly in June. This is preferable for analysis, since this is the timeframe when the global warming signal just started overwhelming everything else.

Compared to 1961-1990, the June maximum over the last 14 years is 2.7F warmer; the July maximum is 0.8F warmer; and the August maximum is 1.3F warmer.

Looking at your data for 1991-2020, which shows minimal warming, I would say a linear trend is not a good approximation. This is a hockey stick pattern, with little warming over decades followed by rapid heating in the past 15 years.

[bluewave]

20 minutes ago, TheClimateChanger said:

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?

The effects will be enhanced closer to the farming areas and reduced somewhat in the more urban spots away from agriculture. My main opening post mentioned the declining highs and rising lows right at the farms. But this general pattern exists to some extent throughout the region.

 

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.

[Blizzard92]

https://www.wired.com/story/the-mysterious-warming-hole-in-the-middle-of-the-us/

[GaWx]

5 hours ago, Blizzard92 said:

https://www.wired.com/story/the-mysterious-warming-hole-in-the-middle-of-the-us/

From this article:

But that doesn’t mean global warming has somehow skipped the central US: In a weird twist, climate change may be partly responsible for this gap.

Interestingly enough, the conditions that contribute to the hole actually begin thousands of miles to the west, in the tropical Pacific. “Changing ocean surface temperatures, partly caused by global warming and partly caused by naturally occurring variability, are producing the downstream changes in atmospheric circulation over the US,” says Gerald Meehl, a senior scientist at the National Center for Atmospheric Research, who wasn’t involved in the new research. “This paper confirms earlier work that these changes in circulation are bringing this cooler and wetter weather into parts of the eastern US.”

 

 This seems like a reach to try to attribute the wetter wx in the Midwest to AGW. This is a very weak argument at best imo. I favor calling it a combo of mainly much higher crop production (which has likely been helped by increased CO2) along with natural variability. Besides, an increase in droughts is supposed to occur due to AGW. 

  I’m not doubting AGW at all (very much unlike Joe Bastardi for example, who’s ignoring scientifically supported facts/evidence). But I do question some of the attempts to attribute too many things to AGW without solid evidence. Overdoing attribution only serves imo to make it more difficult to educate folks about the reality of AGW because I feel it creates straw-men.

[bluewave]

6 hours ago, Blizzard92 said:

https://www.wired.com/story/the-mysterious-warming-hole-in-the-middle-of-the-us/

Thank you very much for posting that great information. I updated the title of this thread to incorporate this new and important study. If there is any way for you to post the full paper beyond the abstract I would really appreciate it. The beauty of science is that our understanding of things can grow based on new research.

 

A cooling trend in summer (May-August) daytime temperatures since the mid-20^th Century over the central United States contrasts with strong warming of the western and eastern U.S. Prior studies based on data through 1999 suggested this so-called warming hole arose mainly from internal climate variability, and thus would likely disappear. Yet it has prevailed for two more decades, despite accelerating global warming, compelling reexamination of causes that in addition to natural variability could include anthropogenic aerosol-induced cooling, hydrologic cycle intensification by greenhouse gas increases, and land use change impacts. Here we present evidence for the critical importance of hydrologic cycle change resulting from ocean-atmosphere drivers. Observational analysis reveals the warming hole’s persistence is consistent with unusually high summertime rainfall over the region during the first decades of the 21^st Century. Comparative analysis of large ensembles from four different climate models demonstrates that rainfall trends since the mid-20^th Century as large as observed can arise (though with low probability) via internal atmospheric variability alone, which induce warming hole-like patterns over the central U.S. Additionally, atmosphere-only model experiments reveal that observed sea surface temperature changes since the mid-20^th Century have also favored central U.S cool/wet conditions during the early 21^st Century. We argue that this latter effect is symptomatic of external radiative forcing influences, which via constraints on ocean warming patterns has likewise contributed to persistence of the U.S. warming hole in roughly equal proportion to contributions by internal variability. These results have important ramifications for attribution of extreme events and predicting risks of record-breaking heat waves in the region.

[Ginx snewx]

https://www.mdpi.com/2225-1154/11/9/179

[Blizzard92]

On 9/20/2023 at 3:29 PM, bluewave said:

Thank you very much for posting that great information. I updated the title of this thread to incorporate this new and important study. If there is any way for you to post the full paper beyond the abstract I would really appreciate it. The beauty of science is that our understanding of things can grow based on new research.

 

A cooling trend in summer (May-August) daytime temperatures since the mid-20^th Century over the central United States contrasts with strong warming of the western and eastern U.S. Prior studies based on data through 1999 suggested this so-called warming hole arose mainly from internal climate variability, and thus would likely disappear. Yet it has prevailed for two more decades, despite accelerating global warming, compelling reexamination of causes that in addition to natural variability could include anthropogenic aerosol-induced cooling, hydrologic cycle intensification by greenhouse gas increases, and land use change impacts. Here we present evidence for the critical importance of hydrologic cycle change resulting from ocean-atmosphere drivers. Observational analysis reveals the warming hole’s persistence is consistent with unusually high summertime rainfall over the region during the first decades of the 21^st Century. Comparative analysis of large ensembles from four different climate models demonstrates that rainfall trends since the mid-20^th Century as large as observed can arise (though with low probability) via internal atmospheric variability alone, which induce warming hole-like patterns over the central U.S. Additionally, atmosphere-only model experiments reveal that observed sea surface temperature changes since the mid-20^th Century have also favored central U.S cool/wet conditions during the early 21^st Century. We argue that this latter effect is symptomatic of external radiative forcing influences, which via constraints on ocean warming patterns has likewise contributed to persistence of the U.S. warming hole in roughly equal proportion to contributions by internal variability. These results have important ramifications for attribution of extreme events and predicting risks of record-breaking heat waves in the region.

I believe the paper should now be open access - sorry for the issues! https://journals.ametsoc.org/view/journals/clim/36/20/JCLI-D-22-0716.1.xml