What tells you that winter is waning and spring is beginning? Tree leaf buds swelling? Longer daylength? First wildflower or robin? Warmer temperatures? Seasons are defined by three types of information: astronomical, meteorological, and phenological. Once upon a time before global warming these three aligned most years. As daylength grew longer and earth’s tilt increased light intensity in the northern hemisphere, warmer temperatures arrived and snow melted. Pussy willows and crocus burst into bloom, tree leaves began to unfurl, birds migrated north, butterflies emerged from overwintering chrysalises and we said spring is here!
Weather and the axial tilt of earth still drive phenology but meteorological aspects are out of kilter, confusing plants and animals. This winter Denver hit 80o, California has phenomenal precipitation, Portland Oregon was snowed in, the eastern U.S. zips between cold snow and sunny warmth, and Miami had record-setting heat. How do we define spring now?
The National Phenology Network (NPN) tracks the status of spring across the U.S. using models based on leaf and bloom data. Their spring leaf data goes back to 1900 and shows 2012 as the earliest spring — until now. In many parts of the country, spring 2017 is the earliest ever. Nashville, St. Louis, Washington DC, Atlanta, Pittsburgh, Columbus and Indianapolis are at least three weeks early, but Phoenix and Los Angeles are a bit late.
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In February, NOAA recorded over 4,400 record highs in the U.S. but only 29 record lows. Spring in the southeastern U.S. is three weeks early, according to NPN data using field observations of lilacs and honeysuckles (phenological data) along with temperature and weather (meteorological data). The cherry blossoms in Washington D.C. might set a record this year for earliest peak bloom ever. Twitter is tracking this year’s record-setting observations under the hashtag #phenology.
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The National Park Service predicts that Washington DC ’s cherry blossoms will reach peak bloom between March 14 and 17 this year. The earliest peak bloom documented is March 15, 1990. The historical average is April 3. Ironically, there’s also a chance the city might see some snow this weekend. Snow and freezing temperatures could slow the bloom or even kill it, but so far cold has never actually stopped the blooms since record-keeping began in 1920. However, unusual weather over the past few weeks has resulted in flower progress variations among different trees. Some are in early bud development while older trees are beginning to bloom. Meteorology is confusing cherry blossom phenology. Washington Post photograph Kevin Ambrose reports.
In my 15 years of photographing the Tidal Basin, I’ve never seen so much difference in bud development among the cherry trees at one time. Our extreme temperature swings over the past month appear to have confused the trees. We are stuck in a roller coaster weather pattern that oscillates between winter and spring weather, and it seems to be keeping the cherry trees a little out of sync.
In some areas, winter didn’t do its thing. Chicago had no measurable snow in January or February for the first time in 146 years. Northern Texas and southwestern Oklahoma had temperatures in the 90’s. As of late February, Miami hadn’t recorded a single day below 50° since December 1. This has never happened in Miami since record-keeping began in 1896.
Miami’s average temperature this meteorological winter, which runs from December through February, was 74.2°F. The previous record of 73.5°F was set in 1932. Miami was founded in 1896 and its temperature record dates back to its founding. Just up the coast, Fort Lauderdale also had its warmest winter, averaging 73.3°F. [...]
Out of 90 days this winter, Miami saw a record setting 69 of them reach 80°F or warmer! The previous record was 65 days, set during the winter of 1988-89.
Community Collaborative Rain, Hail & Snow Network (CoCoRaHS) is a citizen science project to measure and map precipitation across the U.S. Their observations show that except for the northwestern U.S. and far northern New England, most of the nation has experienced a mild winter.
In California and most of the western U.S. precipitation was well above normal. But the central U.S. from northern Arkansas through Missouri and Illinois was drier than usual, so was the mid-Atlantic and Florida. In the Sierras and other parts of the western states, snow levels are greater than seen in the past 50 years with some locales reporting 200 to 500 percent above normal.
The Great Lakes’ ice cover is only 10 percent of normal. Average end of February coverage is about 43 percent, but this year it is only 4.5 percent.
Global warming is driving an early spring throughout the northern hemisphere. In Greenland, a sedge species is beginning spring growth 26 days earlier than a decade ago.
"When we started studying this, I never would have imagined we'd be talking about a 26-day per decade rate of advance," said lead author Eric Post, a polar ecologist in the UC Davis Department of Wildlife, Fish and Conservation Biology who has been studying the Arctic for 27 years. [...]
While how early a plant emerges from its winter slumber depends on the species, the study demonstrates that the Arctic landscape is changing rapidly. Such changes carry implications for the ecological structure of the region for years to come.
"The Arctic is really dynamic, and it's changing in a direction that won't be recognizable as the same Arctic to those of us who have been working there for decades," Post said. "The picture is definitely being reorganized."
While balmy winters and early spring blooms might be appealing to humans, nature’s mosaic intertwines animals and plants. Migrating birds and insects depend on their food and shelter plants being at the proper stage when the animals are present. Plants require pollinators at the right time to fertilize flowers for fruit set, and everyone who depends on the fruits and seeds is affected by poor pollination. A study that examined almost 300 years of records determined that for every one degree Celsius of increased temperatures globally, migratory birds reach their summer breeding grounds a day earlier.
Reaching their summer breeding grounds at the wrong time - even by a few days - may cause birds to miss out on maximum availability of vital resources such as food and nesting places.
Late arrival to breeding grounds may, in turn, affect the timing of offspring hatching and their chances of survival.
Long-distance migrants, which are shown to be less responsive to rising temperatures, may suffer most as other birds gain advantage by arriving at breeding grounds ahead of them.
An early spring can be dangerous, and it doesn’t necessarily coincide with the date of last frost. A killing frost after flowering or fruit set can result in crop failures for human food and limit fruits, seeds, and shelter for wildlife. In much of the U.S. the agriculutural growing season begins about a week earlier than it did in 1960. In 2012, the USDA released a new plant hardiness zone map that shows the zone boundaries shifting north. Due to climate change, spring is happening about 2.5 days earlier every decade.
These kinds of mismatches can upset complex relationships between animals and their environment. In the Arctic, some grasses bloom a month before normal, depriving hibernating animals of a crucial early-spring food source. Snowshoe hares turn white during the winter, and then brown during the summer, so that they can be better camouflaged against the ground. But now that snow is melting earlier in the year, many are still wearing their white coats in the spring mud—making them especially easy for predators to pick off.
Another level of complication results from plants that depend on astronomical spring — when daylength and light intensity triggers spring growth — which can now be out of sync with plants and animals whose phenology is driven by weather. These trees may need pollination by, or serve as food and nesting sites for, wildlife whose behavior (phenology) is determined by meteorological factors.
The hardwood trees that dominate Eastern forests—oak, beech, and hackberry—all need to experience the longer days of astronomical spring before they begin to flower. (Astronomical spring begins this year on March 20, the vernal equinox.) These hardwoods are also the species most protected from a late frost: They can’t be fooled just by a false spring’s warmth; they also need the light of axial tilt. Researchers write that even when these sturdy trees are planted well south of their natural range, in subtropical climates where they could flourish in January or February, they still seek the light signal and never bloom before early March.
Along with the earlier spring and warmer temperatures, tornado season begins sooner with peak season shifting a week earlier over the past six decades. This year wildfires already are burning in Texas, Oklahoma, Kansas, and Colorado. More than 1,000 square miles torched in what might be the largest fire in Kansas’ recorded history. Wildfires have burned nearly 750 square miles in the Texas Panhandle and 540 square miles in Oklahoma.
All of eastern Colorado is classified as either moderately or abnormally dry along with much of Kansas and Oklahoma, and some of northern Texas, according to the U.S. Drought Monitor, a weekly tracker of dry conditions across the U.S.
Don’t let the maps and data fool you into thinking these changes are uniform and explicable. The words scientists use to describe the new seasonal patterns include anomalous, unpredictable, and extreme. Since we have no choice but to live with these changing meteorological and phenological patterns, why not help document them? Join the CoCoRaHS project and submit information about rain, hail and snow in your locale. Nature’s Notebook from the National Phenology Network wants to hear about the plants and animals around you. All the information and training needed is available through their website.
We’re just beginning to explore new definitions of spring and other seasons. Astronomical spring begins in two weeks but in many parts of the U.S. meteorological and phenological spring began last month.
Everyday here in the Daily Bucket we talk about signs of the season around us.
Did you have winter? What’s your spring status?
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