Spring could arrive five weeks earlier by 2100

Buds, birds and animals tell a disturbing story: Spring is arriving earlier. If current trends continue, spring might come as much as five weeks earlier by the year 2100. Such a pronounced change would have a dramatic effect on Minnesota's interconnected web of natural systems. On Thursday's Climate Cast, Kerri Miller and MPR News' Chief Meteorologist Paul Huttner discussed recent findings and took questions from listeners. Here is an edited transcript of their conversation:

Kerri Miller: Paul, where does this study come from?

Paul Huttner: This one comes from Geophysical Research Letters, published by Climate Central this week. It's a pretty reputable publication. Here's the interesting part of this to me: The modeling they did looking at phenology (bud burst, lilac blooms, etc.) shows that spring could come earlier by several weeks by the time we get to 2100. But that shouldn't be a big surprise. Just go back a year. Last year on March 23, I had lilacs leafing out at the weather lab. This has already happened; we had spring four to five weeks earlier last year. It's not going to happen every year — obviously it's not happening this year — but the trends are already established and documented.

Miller: Spring advancing as much as five weeks earlier, that's going to have a serious effect on our ecosystem.

Huttner: It is. And that's the high end of the projections they're looking at. They're saying as an average for the country, more like two weeks, but as you move farther north that could increase. We've already got lines of evidence. Spring is already coming earlier since the 1950s. Lilacs are blooming two weeks earlier, snowmelt in the Rockies is happening earlier every spring. So these things that are happening and these new projects like Project Bud Burst — a group of phenologists tracking these changes throughout the year — have already documented that spring is coming earlier, fall is coming later. The question is, how long will these trends continue?

Simon in Grand Rapids (on the phone): I spend a lot of time in the north woods of Minnesota. Anyone who spends time up there will know about gray jays, commonly called whiskey jacks, that come steal your food from the campsites. On my recent trips up there, they're becoming a lot less common. The suggestion is that when they steal your food, they store a lot of it and eat it later. Now there's a thought that it can't keep the food because it just starts to rot more, so they're having to go farther north where they can store it.

Miller: Is that something we're going to see? Some of the birds that we're used to observing moving farther north because it's getting too warm?

Huttner: That's what folks are saying. A lot of it's based on the trees. What happens is the southern forest — maples, deciduous trees — they start to outcompete the pine and the spruce and they take over. The theory, the trends are that our northern forest in northern Minnesota in the Boundary Waters, where I love to go, will look more like the South as we head through the next 50 to 100 years. The spruce and the pine are moving north. Part of that process is that we get warmer, drier, there's more drought, more stress on the trees, more insects and we get more fires.

Miller: I noticed that the lead scientist on that study we talked about is mentioning the homogenization of the ecosystem. No longer, potentially, parts of the country that look strikingly different from one another, more of a sameness across the ecosystem.

Huttner: The North is warming more quickly than the South. The trees, the plants, the birds and animals that inhabit the South will range North. There's less variation from North to South as there's less variation in temperature from North to South.

Tom in Fridley (on the phone): I've noticed that with the earlier spring and the later falls, that besides drying out and getting warmer, I've seen less bugs. Fewer mosquitoes, fewer honeybees in the backyard, and therefore I've seen fewer bats and fewer birds. I'm wondering if anyone else is noticing that.

Huttner: I don't know if it's been documented. I know we've been in drought for most of the last two years, and that will definitely knock down the bug population. The trends that folks talk about for the longer term are that we're going to see more droughts in Minnesota and the Midwest as we get more evaporation from the soils and more distance in between these rainfall events. It makes sense to me, but I just haven't seen any hard, concrete studies to say that that's the case. But I bet they're out there.

@kerrimpr We have had our dairy cows out on pasture in mid April the past couple springs. Grass greener faster Historically not until May.

— Emily Zweber (@ezweber) March 7, 2013

John in Stillwater (on the phone): I've noticed over my lifetime living in Minnesota, possums have moved farther north. We never used to see possums around the Twin Cities when I was a kid and now they're quite common, and that seems like a long-term indication of changing ecosystems and temperatures.

Miller: In our backyard, we're seeing wildlife, foxes and deer, that we don't usually see.

Huttner: The overall trends, again, fit. As the plants trend north, the animals will trend north. The range of an animal is determined by the temperature at which it can survive, the food it needs to eat. Part of what they're talking about in this study is that those things will change as well. I know we are seeing more birds, more different kinds of animals in Minnesota that we didn't see 40 to 50 years ago.

Miller: After last week, we got an email from Pat Conway. Last week you mentioned the drought that much of the nation is in may be influenced by the changing climate. He wrote, "There's a ton of ice and snow all over my driveway and lawn." In fact, he had a $150 plowing bill in February. All that snow should help the drought a lot.

Huttner: Here's the deal. There's three different kinds of drought. Meteorological drought is when we have below average rain and snow. That had been going on last year and the year before. We ran up 10-inch deficits in moisture across Minnesota. But that has really eased in the last few months. We're above average, slightly, with precipitation since December. The meteorological drought is easing, that's the snow in your yard. Hydrologic drought — that's river, lakes, aquifers — that has been very severe as well. Three to six inches of moisture now in western Minnesota in the snow cover. That will boost rivers and lakes some, but it won't end the drought because we're so far behind. The really important one is agricultural drought. That's the soil's drought. That's where we had those 10-inch deficits. The soils were basically sucked dry late last summer and fall. Last year's crop used up a lot of that resource, so did the trees, so it's very dry. The snow cover has little or no impact on that. The ground is frozen. That won't seep in, it will run off instead into the rivers and lakes. What we need is much above average rainfall in the spring after the thaw.

Miller: How do you take models that look out 50 or 100 years and know that there is some measure of accuracy to the prediction?

Huttner: Because we can model what happened in the past from records like ice cores, tree rings. The other thing is, we're already observing some of these changes. They're already documented for the last 40 or 50 years or so and we can take what's happened and model it through the past, and it fits. It fits absolutely with the increase in greenhouse gases that we're seeing.

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