It seems that everyone in agriculture is discussing weather extremes this season. At the time of this writing, half the counties in the U.S. are experiencing some degree of drought. The expanding area of dry conditions has been part of a 12 month period that had 36,228 record-breaking maximum temperatures across the U.S. In June, the National Climate Data Center (NCDC) reported 86 events that broke and 87 events that tied the all-time highest maximum temperature records. Most recently, July was the hottest month on record in the conterminous U.S. Needless to say, the anomalous heat and dry weather had significant negative impact on summer crops this growing season.
It is important to put all this recent extreme weather in perspective. When I was an undergraduate student studying Meteorology in college, there was a running joke that the announcement of any record-breaking weather event should be followed by the qualifier “since the last ice age.” This joke was the recognition that our period of record is quite short when compared to the millions of years of climate variability and the periodic occurrence of ice ages during the past hundred thousands of years. While climate variability is a natural part of the evolution of our planet, it’s not well understood.
In science-speak, climatic variability is the statistical measure of the “swings” in climatic states, such as the range of warm to cool annual maximum temperatures over a period of years. Climatic anomaly is the deviation of a particular climatic state from both its average and variability, such as the warmest or coolest annual maximum temperature in a hundred years. A climate anomaly is an extreme event that is rare but still part of the climatic record. It is the measure that has the greatest impact on crop development and growth.
The public in general, and growers in particular, would have difficulty preparing for a variable climate, especially one with a high frequency of anomalous events. The obvious reason for this difficulty is that climate by definition represents changes in weather patterns over a long period of time. Climate normals are calculated over thirty years and updated every ten years by the NCDC. Climate trends are tracked over decades. It is therefore not surprising that there is little preparation for changes in climate. By the time a new climatic pattern is established in some geography, the change in normals and the new frequency in extreme events have already been felt by growers. Because of this long delay before observations signal a new climate, meteorologists must rely on the predictions of global climate models or GCMs.
GCMs provide plausible scenarios of future climate states for locations around the world based on a scientific understanding of what has happened in the past. They cannot predict day-to-day weather patterns. They can predict within a quantifiable range of uncertainty, that some geographies will have warmer average temperatures and dryer conditions. While a GCM prediction is not fact, it is a guide to future weather trends and potential changes in the frequency of extreme weather events.
Expecting a grower to prepare for climate variability may seem silly given his or her concerns for weather events just days into the future. However, there may be value in understanding the risk associated with a change in climate. This understanding of risk can be best explained with an example. If a grower in a particular location has experienced a crop-damaging drought once every 30 years, it would make sense to do nothing since this extreme event is rare. However, if model predictions of future climate scenarios for the same location indicate droughts occurring every five years, the grower may want to amend or adjust his or her production practices, such as by adding irrigation. The grower may want to switch to drought-tolerant hybrids since his or her risk for drought will be higher in the future. Crop insurance may also make sense with the expectation of more frequent dry conditions.
The Role Precision Ag Can Play
Precision agriculture, or more precisely precision monitoring, can have a role in a changing climate. First, a grower must keep good records of weather events along with their impact on crop yields in his or her current climate. Second, the same grower must review the predictions of climate change at his or her location and then seek out observations in another geography that currently experiences conditions similar to the new climate. By understanding how crop development and yields are impacted by the current climate in the other geography, the grower can anticipate the future impacts on production in the new climate. By understanding how the future trend in climate will impact his or her crop production, the grower can gradually make changes in the choice of seed, the time of planting, along with other management decisions.
This precision monitoring must extend across the landscape of a farm because climate trends can amplify local weather patterns affecting crop production. For example, dry soils in one part of farm may extend to new areas in a future climate state having less frequent precipitation events. In another example, early season, warmer weather in the future may result in favorable conditions for disease development during more susceptible life stages of a crop. In a less obvious scenario, a grower may plant a crop earlier in season due to warmer temperatures but have the same risk for a late frost.
The recent trends of dryer weather throughout much of the Midwest, coupled with record-breaking temperatures during this summer, should provide ample warning that climate variability is real regardless of the cause. Precision agriculture, especially new techniques such as variable-rate irrigation, can be part of the solution to minimize the risk associated with future climate states. It is just a matter of understanding and implementation.