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Although the topic is still generating a variety of views, including whether it is real or not, changes in weather and climate that are very likely to affect agriculture in many ways are already in place.

Even if there are lingering doubts about the reality of the phenomenon, data which has already been collected strongly suggests that some changes are fairly obvious, according to Chippewa County Extension Service agriculture agent Jerry Clark, who was a presenter at the semiannual farm management update for agricultural professionals.

Weather vs. climate

Clark explained that the information he was presenting is based on his attendance at several events at which the topic was discussed and on research that has been carried by other persons and entities. He noted that individual weather events are separate from climate, which is a longer period trend of weather.

For example, weather refers to the hourly or daily temperature variations and atmospheric events while climate describes weather averages of temperature, precipitation, wind patterns, extreme events and sea levels over periods such as decades or centuries, Clark said. 'Climate is what you expect, weather is what you get.'

Among the special, unusual or periodic weather events are the El Nino and La Nina phenomena based on water temperatures in the Pacific Ocean, a polar vortex (an enhanced Canadian high pressure presence over the United States) and occurrences such as volcano eruptions and glacier movements.

That extreme weather events have become more common in recent years is indicated by the great variances in temperatures at Eau Claire on a certain day — February 27, Clark pointed out. A record low of 22 degrees below zero was set in 2014, while a record high of 59 was set in 2016.

Greenhouse gases

Another change that cannot be challenged is the gradual increase in the concentration of carbon dioxide in the atmosphere from 315 parts per million in 1960 to nearly 390 today, Clark said. While there have been many expressed concerns about this trend, he observed that the higher level of carbon dioxide is beneficial for growing alfalfa and many other plants.

From another perspective, agriculture has been a major contributor of both nitrous oxide and methane to the atmospheric gases. A majority of scientists believe that emission of such gases by human activities is contributing to the trapping of heat in the atmosphere and an increase in temperatures on the Earth's surface, he reported.

A major study on data in Wisconsin is titled Wisconsin Initiative on Climate Change Impacts (WICCI). It is available online under that title or directly at www.wicci.wisc.edu.

A review of temperature trends in the Upper Midwest from 1910 through 2012 shows that seven of the 10 years with the highest daily average temperatures occurred since 1987 (one or two more recent years could be added to that list), Clark reported.

Wisconsin specifics

Although there are variations by region, the average annual temperature in Wisconsin is up by 1 to 1.5 degrees since 1950, according to the data published in the WICCI study. The greatest temperature increases, especially during winter and spring, have occurred in the west central part of the state.

Those changes include rises of 3 to 5 degrees in the nighttime low temperatures in the winter and spring in approximately the western half of Wisconsin since 1950. There have been minimal increases in the southern tiers of counties and even slight drops in those temperature averages in far northeastern Wisconsin bordering the Upper Peninsula of Michigan.

As a result, the growing season has lengthened by 1 to 4 weeks in most areas in Wisconsin during the past 65 years, Clark said. The dates of the last freeze in the spring are now 6 to 12 days earlier while the first fall freeze tends to be 8 to 12 days later. Across the United States, the growing season increases range from 6 days in the Southeast to 16 to 19 days in the Northwest to Southwest.

In comparisons of 1935 to 1947 and 1976 to 1988 in Wisconsin on 55 ecological indicators of spring, 37 have shown calendar advances, Clark noted. They include pasque flowers blooming nine days earlier, American robins arriving 14 days earlier and bloodroots blooming 14 days earlier on average.

Temperature projections

A continuation of that pattern would boost average temperatures by 3 to as much as 9 degrees in Wisconsin by 2055. From a temperature base of 1980, the increases would occur in all seasons throughout the Upper Midwest with summer showing the lowest increase, according to one set of projections.

The annual average for the number of days above 90 degrees would jump from 10 to 25 and the average for over 100 would rise to 5 days. During the winter in Wisconsin, the average daily temperatures would be 5 to 12 degrees higher by 2055 compared to 1980. Temperatures holding at above 70 degrees at night would be detrimental for the pollination of corn, Clark pointed out.

From a base average of 95 freeze/thaw cycles during the 50 years up to the year 2000, that number would drop to as low as 60 by the year 2065. Clark remarked that this could have both good and bad effects for agriculture.

Precipitation patterns

Precipitation patterns have already changed and could change even more, Clark continued. The collected data for the Upper Midwest from 1910 through 2012 found that eight of the 10 wettest years have occurred since 1978.

Summer precipitation changes projected from 1980 to 2090 show major decreases in the south central United States to modest increases in the Upper Midwest's northern tier of states, including Wisconsin. To the year 2050, the change in Wisconsin is projected to increase rainfall in the autumn and winter and reduce snow depth in the winter.

A related change in precipitation is a trend toward less but more extreme events, the forecast projections indicate. Clark pointed out that in 2015 alone portions of Chippewa County had four incidents of 4-inch rainfalls, including two of 7 inches.

Effects on agriculture

For production agriculture, those rainfall pattern changes would increase the likelihood of water runoff and nutrient and soil erosion, create more stream flow, and result in shortages of water stored in soil, Clark warned. He also mentioned an increased recharge of groundwater with an associated risk of contamination due to a higher water table.

Data from Iowa comparing the past 15 years with the previous 15 years shows that more frequent rainfalls shaved 3.7 workable field days during the prime planting period in spring, Clark reported. For April to June across the Upper Midwest, 2.6 workable field days have been lost for that reason, he added.

Rises in humidity associated with more rainfall could affect the production of milk, meat, and eggs, Clark observed. He mentioned the major outbreak of northern corn leaf blight in 2015 and the potential for fungal pathogens and mycotoxins in stored feeds.

Response to risks

While a longer growing season would benefit numerous crops, Clark noted that additional risks from diseases and insects could occur and that the habitat could improve for non-native invasive plants and other species. As occurred in 2012, an early breaking of dormancy or early blooming of fruit trees could result in losses due to a later freeze.

From the combination of positive and negative effects linked to weather events and climate patterns, many Wisconsin farmers have already been making adaptations either as direct results or in combination with other reasons, Clark said.

Among those adaptations are cooling systems for livestock, a step-up in pest management including the growing of crops with genetically modified organisms, earlier planting, the choice of longer season crops, the growing of cover crops, more dependence on crop insurance, conservation tillage and refinements to irrigation and field drainage.

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