and it’s still on track..Taylor looks at past trends, verifying and extending his knowledge with tree rings, to predict repeated patterns in climate. At the 2020 Iowa Power Show in Des Moines, Iowa, Taylor presented a case for another dust bowl occurring in 2025.
"18 years in a row had fairly consistent yields and increase to yields due to corn breeders," Taylor says as he points to a graph. "25 years in a row volatile weather [followed], 18 years fairly consistent, and then we go into 25 of volatile – that's where we are now, in the years that can have greater variation."
Taylor says this is backed up long term by tree rings that stem back 600 years ago by evaluating the growth. "In the trees, you can go back and see what the climate has been in the past and when it repeats," Taylor says.
Looking at the tree rings, the width of the ring reveals how much growth occurred during that year, meaning thicker gaps shows that year had more favorable weather to help generate growth.
When Taylor moved to Iowa, he approached landowners with fallen barns or sheds to cut into wood beams and view the past growth.
Using the knowledge from the tree rings, Taylor says another dust bowl is on the way in 2025.
"2025, what is the magic thing about that year?" Taylor says. "When we looked at those tree rings, there have been dust bowls more than once in this part of the country, and they're 89 years apart – or 90, or 91, or 88, or 87, but 89 on the average – looking back for 600 years from the growth of our oak trees that survived in Iowa."
The pattern has repeated five times from the information gathered from the tree rings. Taylor also says the harshest year in the pattern with extreme cold and wetness in the winter is followed by the hottest and driest summers within two years.
Taylor says the 1800s year took place in 1847, and the 1900s year occurred in 1936 (the Dust Bowl).
Toward the end of the presentation, Taylor pulls up a graph showing the days per year with temperatures over 93 F. and days reaching -10 F..
From 1930 to 2009, Ames, Iowa, has seen a decline in extreme weather days on both sides. The gap between the two extremes projects to minimize the most during the early 2020s.
While the years leading up should be relatively mild with fewer extremely hot or cold days, once the two sides nearly come together, a drastic change emerges.
"What happens right here where these come together?" Taylor says. "Does it seep up slowly like it came down? No. It's a sawtooth in our climate. We get these almost perfect years that we've been seeing lately, and when we get to the end of 'how good can it get?' it jumps [to the top] immediately to the more extremes. It is a sawtooth pattern; be ready for that."
More from Taylor..
Drought is a risk to U. S. agriculture. Risk is manageable and the producer that utilizes historical and forecast weather condition data can compensate for crop loss that may occur. Management according to historical risk is beneficial. Some adjustment to long- term weather risk is feasible using long- lead forecasts and crop weather indicators. The "leading" crop weather indicators are: Subsoil moisture, the stage of the ENSO (El Nino Southern Oscillation), and the phase of the 19- year weather cycle (Benner Cycle).
…
4. Subsoil moisture
Crops are not sensitive to rain. Crops are sensitive to soil moisture availability. Onlyrarelyisrain synonymous with subsoil moisture availability. Inregionswheregrowing season precipitation is not sufficient for optimal crop growth and development, the initial plant available subsoil moisture is critical to crop yields. In western Iowa the growing season precipitation is sufficient for trend line yields only 20% of all years. Initially dry soils result in substantial yield reduction 60% to 70% of the time. The same soil moisture conditions in eastern Iowa result in reduced yields only 50% of the years. In western Iowa a full yield is possible with half of normal subsoil moisture at planting time, but usually the yield is somewhat below the potential (Fig. 3a) when moisture is 25% of normal crop will yield less than half of the potential in 45% of all years (Fig. 3b). Figure 3a,b. Near average crop yields are observed for near average subsoil moisture (a). Crop yield is often substantially reduced (in west Iowa) when subsoil moisture is less than normal (b). (Adapted from Shaw 1983)
Soil water deficits may range from 0 to 10 inches. Deficient
precipitation need not always result in deficit soil moisture as plant available subsoil moisture is only removed from the soil by active vegetation. Precipitation will reduce a deficit, but below normal precipitation does not necessarily result in deficit moisture conditions. The Crop Moisture Index (short-term Palmer Index) is a reasonable approximation of subsoil moisture conditions most years. Risk planning makes use of pre-season soil moisture conditions. Long-lead forecasting of soil moisture has not been effective in risk management.
The historical crop yield risk associated with preseason subsoil moisture content may be combined with the Benner cycle risk. Logically the chance of substantial crop yield reduction is not as great if the subsoil contains optimal crop available moisture as when the moisture is depleted. It should not be assumed that the risk associated with subsoil moisture is independent of the Benner cycle. However, computation of risk assuming the variables to be independent is a reasonable first approximation until linkage is better established.
Subsoil moisture measurement programs have been established in much of the Midwest. The Iowa subsoil moisture survey was initiated in 1954 and is likely the oldest statewide record. With the development of "coupled" forecast meteorological models increased emphasis is likely to be placed on observations of plant available subsoil moisture in the near future.
5. El Nino Southern Oscillation (ENSO)
Since the late 1970s the ENSO has been recognized as an influence on Midwest weather conditions. Above trend crop yields are most likely during the ENSO warm phase and are near trend or below during the cold phase (Carlson, Todey, and Taylor, 1996). Crop response to temperature moderation under warm phase conditions appears to be a greater factor than the influence of the ENSO on precipitation. Historically there have been no widespread droughts during El Niño events and no El Niño summers are included in the hottest 25% of all summers. Random occurrence would imply that one of every four El Nino events would fall in the warmest quarter of all years. (With 0.25 chance of warm conditions for each event, the chance of 23 events without "hitting" a warm year is 1-(0.75x0.75x0.75x.....n=23) = 0.001338 or about one in a thousand). Some of the years have been in the lowest quartile of precipitation, but low precipitation alone is not sufficient to cause drought.
The ENSO condition gives a statistically strong signal for Midwest crop conditions. When the ENSO signal
is combined with the phase of the Benner cycle and the risk associated with subsoil moisture status, the overall forecast value of the factors exhibits sufficient skill to be of value in crop production planning and risk management.
so.. ??
Looking back historically.. good summary of the 1930s.. here.
https://pubs.usgs.gov/wsp/0820/report.pdf
Simple math doesn't look good.
