The "New Normal" Weather

It seems like there is a new flood, tornado, or hurricane every day. Is this the kind of meteorological insanity we need to learn to expect?

Snowpocalypse! Tornadoes! Floods! Climate change may seem like tired old news or ideological propaganda to some of us, but this year's weather has certainly been something to sit up and take notice of. Is this troubling state of affairs a "new normal" served up by climate change?

That's the leading question on many journalists' lips and keypads as they try to squeeze committed answers out of the overworked climate scientists on their contact lists. But this is not necessarily the best angle to take on the story. Most of us already know the answer to that question; short-term weather isn't easily linked to long-term climate, just as a daily bump or dip in stock prices isn't a clear sign of an impending bull or bear market. Of course, that response doesn't make for very compelling media copy, nor does it offer much of anything useful to those who happen to be caught in a bad spin of some local weather-demon's Wheel of Misfortune.

To me, a better look at what's going on is illustrated by what's going on here in the North Country, where upstate New York, Vermont, and Quebec meet in the watershed of Lake Champlain. Unusual amounts of snowmelt have saturated the ground enough to force spring rainwater downhill into the lake, driving its surface two to three feet above the former record highs of the past two centuries and holding it there for weeks on end.

Hundreds of homes are swamped, and rain-fattened rivers are burying roads and bridges while dumping tons of phosphorus-rich silt into the coastal areas, which will soon be ready to spawn noxious algae blooms. One local friend recently described how oddly memorable her Memorial Day weekend was along the western shoreline near Plattsburgh: "Never seen anything like it--there were almost no boats on the lake. The first big vacation weekend of the year, and nobody could launch anything because the boat-lifting machinery in the marinas was under water." That may have been a blessing in disguise, because with the lake's edges sprawling over formerly "safe" properties, even the relatively small waves from boat wakes can chew deep into the loose sediments of formerly protected lawns and farm fields.

A Vermonter whom I'd never met before phoned me in a panic, having heard of a study that I recently conducted on climate change in the Champlain Basin. "I just bought this lakefront property, and now it's flooded. Is it global warming?"

In other words: "Did I just lose a fortune to some permanent new normal?"

Trying to play the role of good scientist, I stumbled through the usual hedged response; we can't definitively link any particular weather event to global warming, etc. After thinking it over more carefully, I think I've found a better, more useful answer. This isn't necessarily a new normal from global warming; rather, it's what a future new normal could look like.

Most of the 16 climate models that I consulted in the study foresaw annual precipitation totals in the Champlain Basin becoming four to six inches higher by 2100 AD if greenhouse gas emissions continue at current rates. In the past, a one-inch annual precipitation increase pushed the lake's surface upwards by four inches, so these models are essentially warning of a possible two-foot jump in mean water level by century's end.

Here comes some required hedging: A few of the models suggested larger or smaller changes, loss of snowpack in a warmer future could shrink tomorrow's spring snowmelt pulses, and a massive and timely switch to non-fossil energy sources could cancel these outcomes. But the majority view of an impending wetting trend with increased carbon emissions does make sense because a warmer atmosphere holds more moisture and is prone to stormy convection. And any large shift in the upper limit of common year-to-year fluctuations, whatever its cause, would look a lot like what's going on in the North Country right now.

In short, our local weather-demons have dropped an important teaching moment on our doorsteps--in some cases with a mighty splash. We may not have reached the new normal yet, but we can probably see it from here. Asking if climate change caused our crazy weather this year misses a more focused and potentially important question: Is this something we should plan for over the long term? In the case of Lake Champlain, at least, the answer appears to be "yes."

[Homepage image: Flickr user meironke; top image: The USGS Flickr stream]


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