Nature's thermometers say spring is springing earlier by 3 days per decade

By: Dr. Jeff Masters , 7:31 PM GMT on March 29, 2013

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In a welcome sign of spring, Washington DC's famous cherry trees are beginning to burst into bloom, with the peak bloom predicted to come around April 5. This is two weeks behind last year's peak bloom date of March 20, which was the third earliest on record, according the Capital Weather Gang at the Washington Post. The only earlier bloom dates in the National Park Service's 92-year record dating back to 1921 were March 15, 1990 and March 17, 2000. The average bloom date is April 4, and the latest bloom date on record was April 18, 1958.


Figure 1. Cherry blossoms on March 21, 2012, in Washington D.C. Image credit: wunderphotographer KEM.

Nature's thermometers are reacting to global warming
Flowering cherry trees are excellent "natural thermometers" that give evidence that the climate is warming. Their flowering time is highly sensitive to temperatures in February and March. Last year's early bloom was triggered by the record-warm "Summer in March" temperatures that gave DC its warmest March on record. February and March temperatures in Washington D.C. have warmed by nearly 3°F over the past century, causing the city's famous cherry trees to bloom, on average, five days earlier than they did in 1921. The earlier blooming times of D.C.'s cherry trees are part of a global trend towards earlier spring blooms. A 2007 study by Parmesan et al. found that Northern Hemisphere spring events such as flowering times, bird and butterfly migrations, and frog breeding times have been occurring an average of 2.8 days per decade earlier in spring since the 1950s, averaged over all species.


Figure 2. Average temperatures in Northeast Virginia, including the northwestern suburbs of Washington D.C., have warmed by nearly 3°F over the past century. Temperatures in 2012 were the warmest on record. Image credit: NOAA/NCDC.


Figure 3. Comparison of the 1990 and 2012 USDA Plant Hardiness Zone Maps. Wintertime minimum temperatures in the U.S. have risen so much in recent decades that the United States Department of Agriculture decided in 2012 to update their Plant Hardiness Zone Map for gardeners for the first time since 1990. The Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The map is based on the average annual minimum winter temperature, divided into 10°F zones. Compared to the 1990 version, zone boundaries in the new 2012 edition of the map have generally shifted one 5°F half-zone warmer than the previous map throughout much of the United States. This is mostly a result of using temperature data from a longer and more recent time period. The old 1990 map was based on temperature data from only a 13-year period of 1974-1986, while the new map uses data from the 30-year period 1976-2005. Image credit: USDA and Arbor Day Foundation

The forecast: DC's cherry trees blooming in early March by 2080?
Using a computer model of spring bloom driven by the expected climate of this century from climate models, a 2011 paper by Chung et al. predicted that peak bloom of Washington D.C.'s cherry trees will come five days earlier by 2050, and ten days earlier by 2080, assuming a middle-of-the-road climate change scenario called A1B. However, carbon dioxide emissions are at record high levels, and humankind is currently on a path likely to cause much greater warming. Under a higher emission scenario, the authors predict that by 2080, the cherry trees will bloom in early March, nearly a full month earlier (29 days) than at present. One major concern the authors point out: shorter and warmer winters can reduce the cold hardening of trees, leaving them vulnerable to frost injury.


Figure 4. Past and projected peak bloom dates of the Yoshino cherry trees in Washington, DC and surrounding areas. The future projections were made under the IPCC middle-of-the-road emission scenario A1B (middle panel) and high emissions scenario A2 (right panel.) Humanity is currently burning oil, coal, and natural gas at a rate that puts us closer to the high emissions scenario. Image credit: Chung et al., 2011, "Predicting the Timing of Cherry Blossoms in Washington, DC and Mid-Atlantic States in Response to Climate Change", PLoS ONE 6(11): e27439. doi:10.1371/journal.pone.0027439

Unusual winter jet stream patterns tied to Arctic sea ice loss may slow down cherry tree blooming changes
However, the authors' cherry tree bloom model did not take into account the fact that unusual jet stream contortions in winter have become increasingly common in recent years, increasing the odds of cold winters over the Eastern U.S. According to a March 2013 paper by Tang et al., "Cold winter extremes in northern continents linked to Arctic sea ice loss", wintertime Arctic sea ice loss can cause an increase in unusual jet stream patterns capable of bringing cold, snowy weather to the Eastern U.S., Western Europe, and East Asia. They theorized that sea ice loss in the Arctic promotes more evaporation, resulting in earlier snowfall in Siberia and other Arctic lands. The earlier snow insulates the soil, allowing the land to cool more rapidly. This results in a southwards shift of the jet stream and builds higher atmospheric pressures farther to the south, which increases the odds of cold spells and blocking high pressure systems that can cause extended periods of unusually cold and snowy weather in the Eastern U.S., Western Europe, and East Asia. Climate scientist Stefan Rahmstorf has an intriguing blog post (translated from the German by Eli Rabbett) that shows a dramatic agreement between temperature and pressure patterns during March 2013, and those expected to occur as a result of Arctic sea ice loss. He concludes, "In my view, the above studies provide strong evidence for a link between Arctic ice loss due to global warming, more frequent winter high pressure air masses, especially over the Atlantic-European part of the Arctic, and an associated influx of cold air to Europe." With Arctic sea ice expected to steadily dwindle in the coming decades, there may be an increase in cold February and March temperatures in the Eastern U.S. that will slow down the shift in cherry tree bloom times.

References
Chung et al., 2011, "Predicting the Timing of Cherry Blossoms in Washington, DC and Mid-Atlantic States in Response to Climate Change", PLoS ONE 6(11): e27439. doi:10.1371/journal.pone.0027439

Parmesan, 2007, “Influences of species, latitudes and methodologies on estimates of phenological response to global warming”, Glob. Change Biol. 13, 1860–1872

Root, T. L. et al., 2005, "Human-modified temperatures induce species changes: Joint attribution", Proc. Natl. Acad. Sci. USA 102, 7465–7469.

Related posts
From Heat Wave to Snowstorms, March Goes to Extremes by Andrew Freedman of Climate Central
Extreme jet stream causing record warmth in the east, record cold in the west (January 2013)
Arctic sea ice loss tied to unusual jet stream patterns (April 2012)
Our extreme weather: Arctic changes to blame? (December 2011)
New USDA Plant Hardiness Zone Map for gardeners shows a warming climate (February 2012)

Have a great weekend, everyone, and I'll be back with a new post on April Fool's Day, appropriate for the occasion.

Jeff Masters

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8. whitewabit (Mod)
Thanks Dr Masters .. Happy Easter to you and family and all that celebrate ..
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Quoting SFLWeatherman:
My first Hurricane season 2013 outlook of the Year is now out
Go to my new website http://firstchoiceweather.com/


Rule #10 Seriously, no spamming. Spamming includes but is not limited to, trying to sell products, trying to solicit traffic for your own blog, trying to solicit traffic for other commercial entities, etc. Do not post links to your own site unless they are directly relevant and even then, use sparingly.
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Thanks,Doc,fascinating information about our changing weather,but can only imagine the comments that will be generated from this story.
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alright... Im back..
Thanks for the new blog.

Happy Easter to you as well

Will he be with a new blog Monday though?
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My first Hurricane season 2013 outlook of the Year is now out
Go to my new website http://firstchoiceweather.com/
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Thanks Doc!
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Thank you Dr Masters for the blog and Happy Easter.

Reposted from prior Jeff Masters blog.

Yes,more rain to come this weekend.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
259 PM AST FRI MAR 29 2013

.SYNOPSIS...FRONTAL BOUNDARY OVER THE FORECAST AREA WILL CONTINUE
TO BRING SHOWERS AND GUSTY WINDS ACROSS THE LOCAL ISLANDS THROUGH
AT LEAST THE NEXT 24 HOURS. DEEP LAYER LOW WILL REMAIN THE DOMINANT
WEATHER FEATURE ACROSS THE NORTH ATLANTIC INTO EARLY NEXT WEEK.
UPPER RIDGE IS FORECAST TO BUILD OVER THE EASTERN CARIBBEAN THROUGH
THE SECOND HALF OF NEXT WEEK.

&&

.DISCUSSION...SATELLITE IMAGES DEPICTED A LOW TO MID CLOUDS
ASSOCIATED WITH A WEAK FRONTAL BOUNDARY COVERING MOST OF THE
FORECAST AREA. RADAR OBSERVATIONS INDICATED SCATTERED TO NUMEROUS
SHOWERS AFFECTING THE ATLANTIC WATERS...MONA PASSAGE AND MOST OF
PUERTO RICO. THESE SHOWERS HAVE DROPPED OVER 4 INCHES OF RAIN
ACROSS PORTIONS OF THE TRUJILLO ALTO AND NORTHEASTERN PUERTO RICO
SINCE MIDNIGHT. OTHER AREAS ACROSS NORTHERN PUERTO RICO SUCH AS
BARCELONETA AND ISABELA RECEIVED AT LEAST 2 INCHES. GLOBAL WEATHER
MODELS ARE IN FAIR AGREEMENT THAT THE FRONT WILL STALL OVER PUERTO
RICO AND THE US VIRGIN THROUGH AT LEAST LATE SATURDAY WHILE DISSIPATES.
A SURFACE HIGH PRESSURE IN THE WAKE OF THE FRONT WILL RELOCATE NORTH
OF THE AREA ON SUNDAY...ALLOWING EASTERLY TRADE WINDS TO SLOWLY
RETURN TO THE ISLANDS. MOISTURE ASSOCIATED WITH THE REMNANTS OF
THE FRONTAL BOUNDARY WILL LINGER UNTIL AT LEAST SUNDAY...PRODUCING
INTERVALS OF CLOUDS AND PASSING SHOWERS FROM TIME TO TIME. A BRIEF
PERIOD OF DRIER WEATHER IS EXPECTED THE FIRST PART OF NEXT WEEK.

&&

.AVIATION...PERIODS OF MVFR ARE LIKELY ALL TAF SITES XCP TJPS AND
TKPK AS FRONT SLOWLY MOVES EAST OVER THE LOCAL ATLANTIC WATERS. ALSO
TJBQ MAY REMAIN IFR BEYOND 30/02Z. SHRA AND OVC CONDS AND MTN
OBSCURATIONS TO REMAIN THRU 30/22Z. LLVL WIND NE TO E 5-10 KT TO
FL050 INCR TO FL100 LATE TODAY. WIND ABV FL100 W INCR WITH HGT.
WINDS AT 40 KFT UP TO 60 KTS.

&&

.MARINE...SCA CONTINUES FOR THE ATLANTIC WATERS AND THE MONA
PASSAGE UNTIL SATURDAY NIGHT. SEAS HAVE BEEN FLUCTUATING BETWEEN
6 AND 8 FEET IN THE NEAR-SHORE BUOYS SINCE THIS MORNING. HOWEVER...
SEAS HAVE DROPPED AROUND 6 FEET THIS AFTERNOON AT THE OUTER BUOY
41043. WINDS ARE EXPECTED TO BE IN THE 15-20 KNOT RANGE ACROSS
MOST OF THE REGIONAL WATERS AND THE LOCAL PASSAGES. WINDS WILL
SUBSIDE SLOWLY DURING THE NEXT 24 HOURS. IN CONTRAST...SEAS MAY
REMAIN AROUND 7 FEET AFTER SATURDAY...DUE TO AN INCOMING NORTH
SWELL THAT WILL ARRIVE ON SUNDAY. THIS MODERATE SWELL MAY BRING
THE SEAS NEAR SCA LEVELS ONCE AGAIN SUNDAY AND MONDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 82 75 83 / 60 60 60 60
STT 74 82 74 85 / 40 60 70 70
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nice spring blog for easter thanks doc
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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