Just don’t expect to see many apple blossoms. Full apple bloom was well over a week ago (see Wenatchee World).
WSU Extension Horticulturalist (and former Honorary Grand Marshall of the Apple Blossom Festival) Tim Smith maintains a “blossom model” to help orchardists time management operations. Smith notes that this year’s bloom is a week earlier than the 30-year average, in spite of the past three weeks of miserably cool weather.
Since flowering is a key indicator of heat accumulation by plants (what scientists call analogues), this year’s early apple bloom is a sure sign of climate change, right?
Actually, no. One year’s weather does not a climate trend make.
In fact, if you do a little digging, you will quickly see that the timing of apple bloom has shifted earlier and later throughout the history of the Apple Blossom Festival, with the earliest bloom date in 1934 and last year’s bloom just about normal. So what gives?
The reality is that climate is complicated and it’s really easy to commit the scientific fallacy of “bias-selecting” for weather data that confirms our pre-conceived conclusions. Like this year’s early apple bloom. While global averages and trends certainly show a multi-decadal warming trend, how the climate manifests itself regionally, locally and seasonally is actually far more important to us than the global averages or trends – because it’s these manifestations that affect our management context.
And, we know that our regional climate has a tremendous amount of variability between years and within a year. Robust statistical analysis of a trend requires that you look at both the average change (mean) and the variance around the mean (standard deviation) to determine whether there is a meaningful trend or not, not just the data that supports your perception. To determine scientifically meaningful trends for average annual temperature and precipitation alone it takes decades of climate data for all the complex variables to sort out. For instance, as Georgine Yorgey recently described, in spite of overall annual warming in the Pacific Northwest, there has actually been a cooling trend in the temperature record for spring over the past couple of decades as the various and complex drivers of climate have manifested themselves in our region.
Once a clear and scientifically meaningful regional and seasonal climate trend is established (if and when it can be), we still have the challenge of the complexity and variability of how that climatic trend manifests itself in the things we actually care about from an agricultural perspective, such as bloom dates and other stages of a plant’s life-cycle, accumulation of mountain snow-pack and timing of runoff, freezes and frosts and other extreme weather events, incidence and severity of plant pests, timing of management operations, etc.
While for most of society, bad weather is usually just a nuisance, farmers and agricultural communities invest a significant amount of capital and management stress to manage the timing-sensitive, down-side risks of climate that can damage a crop – even if that risk is only a few nights of frosts or freezes during the apple bloom. These investments range from orchard wind machines to battle freezes and frosts to technological decision/management aids to water storage projects to complex pest management programs that must balance consumer interests with “keeping the tree alive”. Regardless of the future magnitude or cause of “global average change”, it’s increasingly apparent that managing the complexities and risks associated with climate is an incredible challenge for farmers.
So, if you do make it to Wenatchee for Apple Blossom this weekend and notice that most of the apple blossoms you actually see are the ones that were painstakingly preserved for the parade, take a few moments in the sunshine to contemplate the amazing feat it is for our farmers to produce sufficient amounts of high-quality fruit each year.