Most fruit growers have trouble accepting the idea that human-caused climate change is occurring. They prefer to think recent weather events are just part of a long, mysterious, and continuing cycle. What’s happening now has happened in the past—and it’s just normal. What goes around comes around.
Still, there is disturbing evidence this may not be the case. There are trends.
Fruit trees are blooming earlier. Winters are warmer and wetter. Summers are hotter and dryer.
In the coming weeks, growers along the shores of the Great Lakes will be looking for ice. The Great Lakes did not freeze over last year as they normally do. Deprived of this traditional icebox to keep things cool, when an early warm spell came last March, fruit trees broke dormancy—a month early. They came into bloom only to be smashed by a series of April freezes that kept reducing and ultimately decimated the fruit crop from mid-New York State west across Ontario and Michigan and into Wisconsin and Minnesota—and as far south as the Ohio River.
Great Lakes ice keeps temperatures down longer in the spring—and Great Lakes ice ultimately is the reason why fruit is grown in the region.
Growers are playing it both ways—preparing for the best and the worst. During the Great Lakes Fruit, Vegetable, and Farm Market Expo in Grand Rapids, Michigan, last month, they crowded into a session on changing climate trends and weather risk management that kicked off the three-day show. But in the show’s last session, they also filled a room to hear about “thinning the record 2013 apple crop.” Michigan State University district horticulturist Phil Schwallier said growers should assume the freezes last year pushed the trees into an alternate bearing mode, and they will have to thin heavily or face biennial bearing problems for years to come.
Growers should expect snowball bloom next spring, should prune hard this winter, and begin thinning as early as possible, maybe even at bloom, advised Jim Schupp, the Penn State pomologist who presented thinning advice at the same meeting. Schwallier believes the odds of a severe freeze-out next spring are very small.
The last such event occurred in 1945—warm March, cold April—and weather was similar in 1946, a disturbing fact. But Schwallier said that while the 1945 crop was a bust, the 1946 crop was normal—because there was such a strong bloom after the bust year.
Growers are also buying wind machines. Michigan State University tree fruit educator Amy Irish-Brown, who works with Schwallier and the apple growers on Fruit Ridge north of Grand Rapids, estimated that the number of wind machines in west Michigan orchards will double from about 50 to more than 100 by next season as growers who had the big fans had some fruit—even last year when low temperatures were accompanied with wind, creating advective freeze conditions that are very difficult to offset. Michigan’s apple crop was reduced by 89 percent by the freezes.
Climatologists are not yet willing to state categorically that the climate is changing, or that human use of fossil fuels might be the cause. They speak cautiously, and scientifically. Nonetheless, weather trends seem to be moving parallel to what would be predicted by the rise in carbon dioxide in the atmosphere. That level has reached 390 parts per million, after hovering at about 280 ppm for nearly a million years until the Industrial Revolution and use of fossil fuels began 200 years ago.
Dr. Jeffrey Andresen, Michigan’s climatologist in the Department of Geography at Michigan State University, said the most troubling trend for fruit growers is the increasing frequency and size of extreme events.
“It is very difficult to distinguish the anthropogenic (man-made) signal from natural variability,” he said. “Changes in the frequency of some extremes are consistent with long-term trends, and recent extremes are also generally consistent with future climate projections.
“Extreme events, while a small fraction of weather events, are responsible for the most significant impacts,” he said. Hurricanes and tornadoes are more powerful, rain events in Michigan bring more rain and even floods.
Last year saw the warmest March on record, across the United States. Michigan then suffered its most severe drought in July and August since 1988; in the United States, it was the worst since 1956. Two major summer heat waves were followed by heavy rainfall and fall flooding in Michigan.
“Temperatures in Michigan last March hit 90 degrees, twice, and that has never happened before. On average, March was 14 degrees warmer than normal. It was the warmest March on record. As December began, the year 2012 was the warmest ever in Michigan history,” Andresen said.
Important trends affecting Michigan fruit growers include these:
—There is less ice for less time on the Great Lakes.
—Winters are becoming warmer. The extreme minimum temperature is rising. On the benefit side, less cold-hardy varieties, especially of the most desirable wine grapes, are being grown now.
—Precipitation in Michigan is increasing, but more is falling in winter. Summers are becoming dryer.
—The growing season is starting earlier. In the last 36 years, the start of the season, measured at green up, has moved ahead nine days, an average of a quarter day each year.
—The growing season is getting longer, but more growing degree days are coming in the spring than in the fall.
—More freezing events are occurring after first green up. While March is getting warmer, the number of freezing events occurring in April is not becoming fewer. Thus, there are more freezing events after green up now than in the past. Average temperatures in Michigan rose about 1°F in the previous century, but have risen 2°F since 1980.
—Predictions are for a still warmer and wetter climate in the future. Temperatures in Michigan, given present trends, will rise by 2°F to 3°F by 2050 and by 5°F to 8°F by the year 2100. If this occurs, Michigan’s climate then will be comparable to current conditions 500 miles south, in Kentucky and Tennessee.