Ag Weather Forum

The following are some details in an article called "Beyond the Data" by NOAA climate scientist Deke Arndt that look at some of the prominent climate and weather happenings from the past year 2016. The full article, including graphics, is at this link: https://goo.gl/…

-- Bryce Anderson

First, the disclaimers: This is not a "top five" list of the biggest weather and climate events of the year. There are plenty of those running around. It's simply one climate scientist's view about selected important climate happenings of 2016, and why they speak to our understanding and experience with long-term climate.

WARMEST YEAR (PROBABLY) ON RECORD, GLOBALLY

What happened:

It was another important year for what is perhaps the most overused climate change indicator out there: globally-averaged surface temperature. This metric is very good for one thing: tracking climate change in a broad-brush sense. Beyond that relatively important function, it's not particularly relevant. The data aren't final, but it appears very likely that 2016 will go down as nominally warmer than 2015, which blew away 2014, which was nominally warmer than the rest of the years in modern history.

Why it matters:

Taken individually, especially in a warming world, the "warmest year on record" is not much more than a curiosity item -- a headline atop a much broader story. If the world is warming, and it is, a new "warmest year on record" is inevitable every few years. However, one thing makes this year more notable than the other four "warmest years on record" we've had since 2000. 2016 will make a hat trick for 2014-16: three years in a row setting a new record. That's rare. With the exception of 1939-41, when the NOAA time series was barely in statistical adulthood, this is only time the modern record yields three straight "warmest years on record."

Beyond the Data:

Of course, those 1939-41 years aren't even in the top 30 anymore. The world has warmed -- a lot -- since then. For some perspective of how much, consider this: 1940 was the first year of the record to be warmer than the 20th-century average.

I like to think of long-term change, the kind that has been going on since the early-to-mid 20th century, as riding up an escalator. Transitory bumps from factors like El Nino, are like jumping up and down while you're on the escalator. Yes, a big jump will help you reach new highs, and make a difference between nearby years on the time series. But it's that escalator ride that makes the next record inevitable: even if it's not likely in 2017, it's inevitable.

THE LA NINA THAT COULD, AND THEN COULDN'T, BUT THEN DID

What happened:

El Nino finally faded coming out of the winter of 2015-16, and La Nina appeared inevitable. And then it didn't. And then it did.

Depending on how you're wired, you might see the emergent La Nina of 2016 as one of the wimpier, more non-committal La Ninas on record, or you might see it as a survivor, overcoming tough headwinds (literally) to finally get the ocean and atmosphere on the same page. Well, kind of. This one certainly won't go on the Mt. Rushmore of La Ninas.

Why it matters:

La Nina is part of the El Nino/Southern Oscillation phenomenon, or ENSO. It can be influential in how our seasons play out, especially regionally, and especially during the non-summer months. I won't waste your time here talking about ENSO, we have a whole blog, written by some of the best in the business, dedicated to ENSO. (See http://bit.ly/…)

Beyond the Data:

But here's the thing. Despite being something of an ugly and scrawny duckling in the La Nina family picture, that La Nina coincided with record and near-record dryness here in the Southeast. And autumn and winter dryness in the Southeast is kind of a La Nina calling card. (See http://bit.ly/…) The national map isn't a perfect match for La Nina -- no monthly map is -- but a dry Southeast is a preferred pattern for La Nina.

LOUISIANA, HERMINE, AND MATTHEW

What happened:

These three events brought colossal rains to the South in August, September and October, respectively. The National Center for Environmental Information (NCEI)'s Billion Dollar Disaster tracker has already confirmed the Louisiana event as causing roughly $10 billion in damages. Losses related to Matthew will also surely make the Billion-Dollar list.

Why they matter:

The Atlantic Ocean has been a fairly active hurricane producer in recent years. Despite this, the U.S. has quite improbably dodged, for more than a decade now, a direct hit from a major hurricane (defined as a Category 3 or greater hurricane at the time of landfall). But we haven't dodged huge impacts. In 2012, Sandy was technically undergoing transition to an extra-tropical storm when it made landfall, but had massive impacts.

The flooding in Louisiana was related to a tropical disturbance, but it wasn't even organized enough to get a name. Matthew was a historic storm earlier in its life cycle, and traced Florida's and Georgia's Atlantic coasts as a major hurricane, with major-hurricane type winds and storm surge, but technically made landfall as a Category 1 (not "major") storm.

Beyond the Data:

Even outside of the context of climate change, the inland flooding associated with tropical storms is often the big killer. These events were no exceptions. The rainfall and flooding were catastrophic.

However, they dovetail with the broader fact that the Southeast -- and, more generally speaking, the eastern half of the country -- is seeing a large increase in the number and importance of large rainfall events. In a statistical sense, these events will go down as a few more data points in a trend that is crystal clear: the eastern U.S. is getting its precipitation in larger doses, and those larger doses are making up more and more of the average annual rainfall budget.

DROUGHT GOES NATIONAL

What happened:

Early in 2016, the Western U.S. was mired in a multi-year drought. Back-to-back-to-back-to-back seasons in the West had been either very dry, very warm, or both, leading to drought, accompanied by disappointing snowpack, in general. Thankfully, the Northwest improved significantly during 2016, and even the Southwest saw some modest improvements in places. But in the east, drought blossomed in the Northeast and exploded across the Southeast. Wildfire complexes dotted the Southeast, especially during autumn.

Why they matter:

Drought is an almost ever-present hazard in our American climate, and has been for centuries. For a combination of reasons, drought is the "quiet hazard." It's not telegenic, or particularly visually compelling. It rarely provides heart-pounding drama. It creeps over long timescales, out of the foreground. But what it lacks in attention-grabbing antics, it compensates for by being relentlessly effective in causing pain, to the economy, to public health, to mental health, and to our water supply. In most years, especially those that don't feature big hurricane landfalls, drought is the costliest natural hazard that occurs.

Beyond the Data:

We often think of drought as a supply issue, in which there's not enough precipitation to go around. But it's also a demand issue, even before human use of water. The first party to demand water from the ground is the same one that put it there: the atmosphere. A warmer atmosphere is a thirstier atmosphere -- it will take back more water through evapo-transpiration (ET, a term that combines evaporation with transpiration, which is the release of water vapor from plants). Precipitation being equal, a hot drought is droughtier than a cool drought.

ALASKAN HEAT

What happened:

At times this year, Alaska's temperatures were literally off the charts. No, seriously. They broke our map legends. Alaska skated to its warmest year on record, by 1.6 degrees Fahrenheit. That's a lot. (See http://bit.ly/…)

Why it matters:

Alaska is America's crucible of change. Much of Alaska sits in the Arctic, which, not coincidentally, is the globe's crucible of change. The Northern Hemisphere's high latitudes are changing more rapidly than any other major geographic region on the planet, and taking Alaska with them.

Like most things climate, temperature is only one indicator of change. In the Arctic, more so than just about anywhere else on the planet, we see different climate elements mutually reinforcing the changes set in motion by global-scale warming. Climate scientists, perhaps ironically, call this "positive feedback," and it goes something like this: warmer temperatures lead to smaller sea ice cover, which leads to more warming of the waters, which lead to smaller sea ice cover. Or, alternatively, warming leads to less snow, which leads to warming, which also leads to shrubbier and darker vegetation, which reinforces warming. And so on.

Beyond the Data:

There might not be a clearer example of this feedback than September and October in Alaska's North Slope. These are the months surrounding the time when Arctic sea ice retreats to its annual minimum -- it's smallest footprint of the year. In the past, on average, the retreat didn't make it very far from Alaska's Arctic coast, and the sea ice, on average, and returned during October. Now, it retreats well offshore and October returns are largely a thing of the past.

All of that open water during these two months brought profound changes to the climate of the North Slope since just 2000. The result is striking: look at the September-October temperatures there. It's not that the place is hitting new records, which it is, it's that a new normal, much different from the previous one, has taken root.

In southern Alaska, the last two years have seen large scale wildfire. It's not easy to separate the role of climate change and climate variability, but record warmth and considerable lack of snow cover, both more likely in a warmed world, played a role. (See http://bit.ly/…)

(ES/)

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