CARBONDALE — Earlier this month, the signs emerged one by one: The crocuses came up. Then the magnolias bloomed. Spring peepers started chirping in the marshes. Temperatures soared into the 70s, and springtime, it seemed, was here — except not really.
Southern Illinois has experienced record-shattering temperatures this February. But is the false spring attributable to climate change, or is it just a random burst of unseasonable weather?
Justin Schoof, a climatologist and the chair of Geography and Environmental Resources at Southern Illinois University Carbondale, said the study of climate change involves two parts: detection and attribution.
“The detection part is, is there a change? Have we measured it? That’s easy to answer … the oceans are warming, the middle atmosphere is warming, ice caps are melting, we have lots of different examples of warming in the system that tell us, yes, this is happening,” he said.
But when it comes to attributing a single event like this year’s early spring to climate change, experts tend to exercise caution. That’s because there are natural fluctuations in weather over time.
“If the world were five degrees Celsius warmer than it is today, you would still have cold winters once in a while. You would still have dry summers and wet summers. You would still have droughts and floods. You’d still have heat waves, you’d still have cold waves,” Schoof said.
One metric used to assess seasonality, Schoof said, is called the frost-free season length, which is the number of days between the last freeze in the spring and the first freeze in the fall.
“That has increased in Illinois by about a week in the last 100 years. So that’s substantial,” Schoof said.
“So even though the spring is coming earlier and earlier on average, there are still years we have a late freeze, and the damaging part, then, is when you have a warm period and then a freeze. These are referred to as false springs. So that’s really what we’re experiencing now,” he said.
Ramifications of a false spring
The last time Southern Illinois experienced a false spring was in March 2012, when a warm spell preceded a period of prolonged freezing.
“You might remember that in 2012 … the peaches were wiped out. There were no peaches. You had to go to Schnucks and buy peaches from other places, because you couldn’t get peaches at the farmer’s market,” Schoof said.
Fruit trees are especially vulnerable to hard frosts after they reach the flowering stage. Mike Flamm, co-owner of Flamm Orchards in Cobden, said the buds on his apple and peach trees are swelling about three weeks ahead of schedule; a few more unusually warm days could cause them to blossom. If that happens, a hard frost could be devastating to his crop.
For now, the extended forecast is looking good, he said, and there’s nothing to do but hope the temperatures don’t go back up.
“The best thing we need right now is some cool weather to keep those buds from advancing further,” Flamm said.
Brad Genung, winemaker at Owl Creek Vineyard in Cobden, said his grapes were pumping up groundwater last Friday. Soon the buds will start swelling and the plants will start pushing out leaves. It’s exciting, but also nerve-wracking, he said.
“The other side of it is that gnawing feeling that all that wonderful green stuff is going to get out there and then you’ll have a freeze, which in our world is pretty bad,” Genung said.
The whole process is happening three weeks sooner than usual, he said.
“I think that in our record keeping — our stuff goes back to 1980 — I don’t think we’ve ever seen a bud break this early. At the rate we’re going, we’ll probably see it late next week,” he said.
But the unseasonable weather is advantageous to some cultivators. Jill Rendleman of All Seasons Farm in Cobden said her farm specializes in greens and lettuces, which tend to like the warm days and cool nights we’ve experienced this winter.
“Mostly what this weather means for us is just managing the variability of it. It’s that it gets cold and hot within 48 hours,” Rendleman said. “I tell you more what I’m worried about, is having a really hot summer, because this is just so hot so early.”
According to Schoof, a hot summer is one of many possibilities. During 2012’s false spring, the early green-up drew groundwater for the vegetation, and there wasn’t much rain. That led to a summertime drought.
“So when people are saying how happy they are about the spring warmth, they might not be happy when it’s 105 this July like it was (in 2012),” he said. “But there’s no guarantee that’s how things will evolve.”
The false spring could also spell trouble for the bees. Sedonia Sipes, a plant biodiversity and conservation ecology researcher at SIU, studies pollinators. Some native species of bees are specialists, pollinating just one type of plant, and work for just a few short weeks every spring. The timing has to be just right.
“So for either of those interacting partners, if the timing gets shifted so that they’re out of sync, that could be bad for both the plant and the pollinator, and that’s just assuming that it’s getting warm early. Who knows what’s still in store for us — we might have some really cold weather coming up, in which case, that could really knock down pollinator populations,” Sipes said.
If a hard freeze does occur this spring, the pollinator population could take years to rebuild, and some plants might not be able to reproduce for the year, Sipes said.
Seasonal forecasts are notoriously poor, Schoof said, so there’s no surefire way of knowing whether we’ll move toward normal conditions or have a snowy March. There’s a good chance winter isn’t over.
“I’m not ready to open the Carbondale pool and go swimming, or anything like that. It’s really too premature for that,” Schoof said.