In phenology, season creep refers to observed changes in the timing of the seasons, such as earlier indications of spring widely observed in temperate areas across the Northern Hemisphere. Phenological records analyzed by climate scientists have shown significant temporal trends in the observed time of seasonal events, from the end of the 20th century and continuing into the 21st century. In Europe, season creep has been associated with the arrival of spring moving up by approximately one week in a recent 30-year period. Other studies have put the rate of season creep measured by plant phenology in the range of 2–3 days per decade advancement in spring, and 0.3–1.6 days per decade delay in autumn, over the past 30–80 years.
Observable changes in nature related to season creep include birds laying their eggs earlier and buds appearing on some trees in late winter. In addition to advanced budding, flowering trees have been blooming earlier, for example the culturally-important cherry blossoms in Japan, and Washington, D.C. Northern hardwood forests have been trending toward leafing out sooner, and retaining their green canopies longer. The agricultural growing season has also expanded by 10–20 days over the last few decades.
The effects of season creep have been noted by non-scientists as well, including gardeners who have advanced their spring planting times, and experimented with plantings of less hardy warmer climate varieties of non-native plants. While summer growing seasons are expanding, winters are getting warmer and shorter, resulting in reduced winter ice cover on bodies of water, earlier ice-out, earlier melt water flows, and earlier spring lake level peaks. Some spring events, or "phenophases", have become intermittent or unobservable; for example, bodies of water that once froze regularly most winters now freeze less frequently, and formerly migratory birds are now seen year-round in some areas.
The full impact of global warming is forecast to happen in the future, but climate scientists have cited season creep as an easily observable effect of climate change that has already occurred and continues to occur. A large systematic phenological examination of data on 542 plant species in 21 European countries from 1971–2000 showed that 78% of all leafing, flowering, and fruiting records advanced while only 3% were significantly delayed, and these observations were consistent with measurements of observed warming. Similar changes in the phenology of plants and animals are occurring across marine, freshwater, and terrestrial groups studied, and these changes are also consistent with the expected impact of global warming.
While phenology fairly consistently points to an earlier spring across temperate regions of North America, a recent comprehensive study of the subarctic showed greater variability in the timing of green-up, with some areas advancing, and some having no discernible trend over a recent 44-year period. Another 40 year phenological study in China found greater warming over that period in the more northerly sites studied, with sites experiencing cooling mostly in the south, indicating that the temperature variation with latitude is decreasing there. This study also confirmed that season creep was correlated with warming, but the effect is non-linear—phenophases advanced less with greater warming, and retarded more with greater cooling.
Shorter winters and longer growing seasons may appear to be a benefit to society from global warming, but the effects of advanced phenophases may also have serious consequences for human populations. Modeling of snowmelt predicted that warming of 3 to 5 °C in the Western United States could cause snowmelt-driven runoff to occur as much as two months earlier, with profound effects on hydroelectricity, land use, agriculture, and water management. Since 1980, earlier snowmelt and associated warming has also been associated with an increase in length and severity of the wildfire season there.
Season creep may also have adverse effects on plant species as well. Earlier flowering could occur before pollinators such as honey bees become active, which would have negative consequences for pollination and reproduction. Shorter and warmer winters may affect other environmental adaptations including cold hardening of trees, which could result in frost damage during more severe winters.
Season creep was included in the 9th edition of the Collins English Dictionary published in London June 4, 2007. The term was popularized in the media after the report titled "Season Creep: How Global Warming Is Already Affecting The World Around Us" was published by the American environmental organization Clear the Air on March 21, 2006. In the "Season Creep" report, Jonathan Banks, Policy Director for Clear the Air, introduced the term as follows:
While to some, an early arrival of spring may sound good, an imbalance in the ecosystem can wreak havoc. Natural processes like flowers blooming, birds nesting, insects emerging, and ice melting are triggered in large part by temperature. As temperatures increase globally, the delicately balanced system begins to fall into ecological disarray. We call this season creep.
The term "season creep" has been applied in other contexts as well:
Season creep n. Earlier spring weather and other gradual seasonal shifts caused by global climate change.
...season creep, earlier spring weather and seasonal shifts caused by global climate change
It's a classic case of the newly identified phenomenon of season creep, where Winters are warmer and Spring arrives earlier.
SI first leaf dates, measuring change in the start of 'early spring' (roughly the time of shrub budburst and lawn first greening), are getting earlier in nearly all parts of the Northern Hemisphere. The average rate of change over the 1955–2002 period is approximately -1.2 days per decade.
Shifting plant phenology (i.e., timing of flowering and other developmental events) in recent decades establishes that species and ecosystems are already responding to global environmental change. Earlier flowering and an extended period of active plant growth across much of the northern hemisphere have been interpreted as responses to warming.
Did spring seem to arrive a bit earlier than usual this year in your part of the world? That wouldn't be surprising, because we seem to be undergoing season creep: earlier spring weather and other gradual seasonal shifts, particularly those caused by global climate change.
SEASON CREEP n. Spring seemed to come early this year--and summer lasted a bit longer. What's to blame? Most scientists say global warming.
...the west arm of Grand Traverse Bay ... has only frozen over five times since 1987,.... Between 1851 and 1980, [it] froze at least seven years per decade, ... the bay-freezing trend shows "a long-term gradual decline with a significant decline in the past 25 to 35 years."
In fact, due to global warming, spring across the Northern Hemisphere arrives a week or more earlier than it did 30 years ago, a phenomenon starting to be known as "season creep."
Spring was beginning on average six to eight days earlier than it did 30 years ago, the researchers said.
Phenology is a sensitive biosphere indicator of climate change. Long-term surface data and remote sensing measurements indicate that plant phenology has been advanced by 2–3 days in spring and delayed by 0.3–1.6 days in autumn per decade in the past 30–80 years, resulting in extension of the growing season.
While the full impact of global warming is still to be experienced, many scientists are warning that it is responsible for earlier springs leading to longer summers.
We examined a 25-yr record (1981–2005) of flowering times for 97 trees, representing 17 species and hybrids of cherry (Cerasus sp. or Prunus sp.) grown at Mt. Takao, in Tokyo, Japan. The cherry trees flowered earlier over time, by an average of 5.5 d over the 25-yr study.
The longest and best known phenological records come from the Far East and Europe, including ... the 1300+-year Kyoto cherry blossom time series ... These longterm historical records can serve as proxies for temperature where thermometer data are unavailable.
Finally, there is the Cherry Blossom Festival in Washington, DC, each spring. On average the two principal species, Prunus serrulata (Kwanzan cherry and other varieties) and P. X yedoensis ( Yoshino cherry), bloom six and nine days earlier, respectively, than they did in 1970.
The expected changes in phenology will have a substantial effect on the reproduction, distribution and productivity of trees as the coincidence of ecosystem processes, such as flowering and the emergence of pollinators, is disrupted. Some plants may also become less resistant to environmental challenges. For example, shorter and warmer winters can reduce the cold hardening of trees, leaving them vulnerable to frost injury.
...significant trends (P≤0.05) towards an earlier spring (e.g. sugar maple, rate of change=0.18 days earlier/yr), consistent with other studies documenting measurable climate change effects on the onset of spring in both North America and Europe. Our results also suggest that green canopy duration has increased by about 10 days (e.g. sugar maple, rate of change=0.21 days longer/yr) over the period of study.
The evidence points to a lengthening of the growing season of ca. 10–20 days in the last few decades, where an earlier onset of the start is most prominent. This extension of the growing season has been associated with recent global warming.
...earlier springs — an idea known as "season creep" — may or may not be related to long-term warming trends. Yet the reality of year-to-year weather weirdness recently, coupled with the ever-present impulse to outsmart Mother Nature, has prompted more than a few gardeners to shun conventional horticultural wisdom.
Knoxville is now in hardiness Zone 7, a zone where more southern trees and shrubs flourish. The zone shift can be seen all across the northern half of the state. It effectively means plants that once had difficulty growing here are now finding it easier to thrive, said Lisa Stanley, master gardener at Stanley's Greenhouses
Freeze and breakup dates of ice on lakes and rivers provide consistent evidence of later freezing and earlier breakup around the Northern Hemisphere from 1846 to 1995. Over these 150 years, changes in freeze dates averaged 5.8 days per 100 years later, and changes in breakup dates averaged 6.5 days per 100 years earlier;
Various studies have shown that changes over time in spring ice-out dates can be used as indicators of climate change.... Ice-out dates have become significantly earlier in New England since the 1800s
Research by [USGS hydrologist Glenn] Hodgkins and USGS scientist Robert Dudley also shows changes in early-spring stream flow across eastern North America from Minnesota to Newfoundland. Rivers are gushing with snow- and ice-melt as much as 10 to 15 days sooner than they did 50 to 90 years ago, based on USGS records.
North America's Great Lakes are reaching their spring high-water levels a month earlier than they did when records began in 1860. Levels normally rise in the spring as snow melts, but regional temperatures have been rising for the past 90 years, and winter ice cover has been shrinking.
A particularly interesting lake ice record comes from Lake Champlain where they record the ice in date.... Of more significance is the fact that the ice has not frozen in the area of observation in 16 of the past 30 years.
Grand Traverse Bay ... froze at least seven winters out of every 10; the rate slipped in the 1980s. In the 1990s, the bay froze only three times. So far this decade, once. Observers see that as one more sign of what some call "season creep," or evidence of global warming.
...Jan Pendlebury, executive director of the New Hampshire chapter of the National Environmental Trust, said... 'Global warming is forcing changes to the quintessential indicator that spring has arrived: return of the robin. Recent years have documentation that rather than flying south with other feathered friends, many populations of robins are becoming year-round residents, not only in the southern tier of the state, but as far north as Jackson.'
Our results showed that 78% of all leafing, flowering and fruiting records advanced (30% significantly) and only 3% were significantly delayed, whereas the signal of leaf colouring/fall is ambiguous.
Ecological changes in the phenology and distribution of plants and animals are occurring in all well-studied marine, freshwater, and terrestrial groups. These observed changes are heavily biased in the directions predicted from global warming...
The model was applied over the whole low arctic region from 1958 to 2002. In North East Canada and North East Russia, no remarkable trend is found in the timing of green- up, whereas a ten-day advance is recorded in the last few decades in North Alaska and in North West Siberia.
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There is a statistically meaningful relation between inter-annual changes in the spring phenophase and the spring temperature in China for the last 40 years.... The response of phenophase advance or delay to temperature change is nonlinear.... the rate of the phenophase difference with latitude becomes smaller too.
A preoccupation with environmental issues, a favourite topic of [British Conservative Party leader David] Cameron's, is also reflected in new phrases such as "carbon footprint", "carbon offsetting" and "season creep", used to describe the changing length of the seasons thought to be caused by climate change.
"Hoodies", "season creep" and "barbecue stopper" are among hundreds of new words and phrases included in an updated version of an English dictionary.
Earliest Citation:… Jonathan Banks, 'Season Creep: How Global Warming Is Already Affecting The World Around Us,' National Environment Trust, March 21, 2006
Call it season creep. First came the shift to 162 games, a change that made it, among other things, impossible to compare Roger Maris' 61 home runs to Babe Ruth's 60.
'Season creep' has expanded the time an intercollegiate athlete must devote to his or her specialty. No sport should be year-round or nearly so.
And it is money, of course, that is responsible for campaign season creep. If you don't raise money early -- gobs and gobs of it -- you'll find yourself on the fundraising super highway with roller marks over your body, where your opponent's war chest plowed over you.
And so does the culture, with a commercializing of himself that Santa deplores even as he has watched the holiday season creep back to Labor Day.