On the East Coast of Canada, an agricultural success story has quietly emerged in Nova Scotia: a new wine industry has taken hold. It has a story to tell about climate change.
Two of the researchers who are closely investigating the grape growing industry in this region are Dr. Harrison Wright and Jeff Franklin, of the Canadian Government’s Kentville Research and Development Centre. Their report on the impact of climate change on the growing season has underscored a major long-term climate change effect.
For those in the grape growing industry, a critical factor is the health of the young grape leaves, which can be killed by cold temperatures below freezing. The date in a new growing season in the Spring when the leaves are out of danger of freezing is called the “last Spring frost date”; the date at which the grapes are in danger in the Fall at the end of the season is called the “first Fall frost date”.
On average, the last spring frost occurs 18 days earlier in 2021 than it did in 1913.
In 1913, the predicted last spring frost date was May 26. Fast forward to 2021, and we see that the date has shifted to May 8.
And the first fall frost now occurs 22 days later.
This means that on average, since 1913, the growing season has extended 40 days. The frost has been held back in the Spring and held off in the Fall by more than one month
The climate had changed that much over the years.
The measure of heat energy that is available for plant growth is called “Growing Degree Days” (GDD). The GDD starts from point on the calendar when the weather is warm enough that the plant can start growing, and continues until the weather gets cold enough that growing stops.
The research paper is quick to point out, however, that the GDD is highly variable: “we can only be 95% confident that the last spring frost will fall within ± 3 weeks of our predictions.” The late frost in 2018, for example, fell outside that forecast, which already includes a wide scope for variation.
Nevertheless, the general trend is visible and irrefutable: climate change is a fact and can be seen in records dating back more than a century.
By coincidence, the first measured evidence of climate change was made only a few years before that, in 1911. That was when human activities – which have been affecting climate since the mid-1800s – started to produce the atmospheric gases in quantity that have trapped more of the Sun’s energy in the Earth system. This extra energy has warmed the atmosphere, ocean, and land, and widespread, and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.
Most of the warming has occurred in the past 40 years, with the seven most recent years being the warmest.
The idea that the planet is warming has a long paternity. Two hundred years ago, the French mathematician Joseph Fourier (1768-1830) calculated that an Earth-sized planet, at our distance from the Sun, ought to be much colder. He suggested something in the atmosphere must be acting like an insulating blanket. In 1856 American scientist Eunice Foote discovered that blanket, showing that carbon dioxide and water vapor in Earth’s atmosphere trap escaping infrared (heat) radiation.
Today’s dramatic realization of the climate case starts with Charles Keeling’s work in 1954. His research focused on a new carbon isotope analysis that could identify “changes in the atmosphere” caused by the burning of coal and petroleum.
The significance of his work was realized immediately. A researcher at the California Institute of Technology wrote of the 1954 finding that “The possible consequences of a changing concentration of the CO2 in the atmosphere with reference to climate, rates of photosynthesis, and rates of equilibration with carbonate of the oceans may ultimately prove of considerable significance to civilization.”
Keeling’s papers “contain smoking gun proof that by at least 1954, the fossil fuel industry was on notice about the potential for its products to disrupt Earth’s climate on a scale significant to human civilization,” said Geoffrey Supran, an expert in historic climate information at the University of Miami.
Keeling died in 2005 but his seminal work lives on. Currently, the Earth’s atmospheric CO2 level is 422 parts per million, which is nearly a third higher than the first reading taken in 1958, and a 50% jump on pre-industrial levels.
The primary heat-trapping emissions have pushed global temperatures to higher than anything previously experienced in human civilization.
One organization that has been pushing back against the carbon emissions driving the change is advocacy group ‘Job One For Humanity’. ‘Job One’ Executive Director Lawrence Wollersheim stated that “The evidence is plain and powerful. This has been going on for 70 years’ and it’s time we took concerted action to repair the damages caused by the climate crisis.”
A group that would not disagree is the Grape Growers’ Association of Nova Scotia. President Bernie Thorne identifies the variability of the growing season as one of the major hurdles faced by his membership: “Knowing about Degree Days is an important factor for our success,” he stated, “It’s not only about the viability of a crop during one season, but about the type of grapes we plant with an eye to future years of production.”
Nova Scotia is at the climate limit for grape growing. Short season hybrids in ideal growing sites have created award-winning wine for an industry that is only decades old – in comparison to historic sunnier regions where grape growing has been a tradition for several thousand years.
So while it may seem that climate change would be an advantage in lengthening the growing season, in reality, the industry took off 50 years ago when GDDs were less than today. Anything beyond that, then, is a toss-up in value against the climate uncertainty contained in the climate change add-on disasters like hurricanes, flooding, cold spells, rain bombs, wind storms (Derechos,) erosion, and intense storms.
It is, in a word, satisfying to be a proof-point for climate change, but from an agricultural perspective, it is time to stop.
While we still have a good wine to enjoy with our victory over rising temperatures.
Because grapes speak the truth about many things…including climate change.
