In the 1950s, the seasons occurred in a predictable and relatively even pattern in the Northern Hemisphere. Flowers bloomed around April. Children planned summer adventures starting in June. Leaves dropped in September. Ski trips began in December.
But recently, the seasons have been out of whack. Over the past seven decades, researchers found high summertime temperatures are arriving earlier and lasting longer in the year because of global warming.
This summer was no exception. In parts of California, which saw its hottest summer on record, unusually warm temperatures arrived in May. Shasta Dam posted its third warmest May on record, a harbinger of a record melt season for the glaciers on the summit of Mount Shasta to its north. Sacramento logged its fifth warmest May.
Folsom Lake during a drought in Granite Bay, Calif. on Aug. 27. (David Paul Morris/Bloomberg)
In the Pacific Northwest, a record-breaking heat wave in late June also occurred much earlier than the region is accustomed to. On June 28, Seattle reached 108 degrees and Portland reached 116 degrees.
“The old rule for our area was typically from the Fourth of July on, you could expect some hot weather,” said Michael Brady, an economics professor at Washington State University. “So not only was the level of the temperatures unprecedented, it was also at least a couple of weeks before you would even expect high temperatures.”
Pacific Northwest heat wave was ‘virtually impossible’ without climate change, scientists find
Unusually hot weather also lasted longer than usual in parts of the Lower 48 states as a late-season heat wave scorched the West in the second week of September. Denver hit 99 degrees on Sept. 10, its highest temperature recorded so late in the season. Earlier that week, Death Valley reached 122 degrees, the highest temperature observed so late in the year anywhere on the planet.
As we mark the end of summer and the fall equinox on Wednesday, fall and winter may not offer much reprieve. Research shows summers are expanding while spring, autumn and winter are becoming shorter and warmer with significant impacts for people and the environment.
In April 2018, a sizable snowstorm blanketed several towns in New Jersey in what seemed like a freak occurrence. In March 2012, unusually warm temperatures in Michigan caused vegetation to emerge from dormancy early, but then were subsequently destroyed by freezing weather in April.
As more unusual weather reports popped up over the years, researcher Yuping Guan was inspired to examine how seasonal cycles were changing. He and his colleagues analyzed temperature data from 1952-2011 and found the four seasons no longer occur equally and had irregular onsets.
In the Northern Hemisphere mid-latitudes, the length of summer increased from 78 to 95 days — or about 4.2 days per decade from 1952-2011. Winter contracted from 76 to 73 days, or 2.1 days per decade on average. Spring decreased from 124 to 115 days, and autumn shrank from 87 to 82 days; each shrank about one day per decade. All seasons were warmer. The most obvious seasonal length changes occurred around the Mediterranean and the Tibet Plateau.
Without changes to mitigate global warming, summer could last nearly six months, study finds
Guan wrote in an email that it’s difficult for people to feel the effects of a small rise in global temperature over many decades, but that the changing length of seasons is something “everyone can understand.”
The onsets of all seasons also changed. Spring started 1.6 days earlier each decade, and summer started 2.5 days earlier. Autumn was delayed by 1.7 days per decade, and winter was delayed by 0.5 days. The delayed winter was the most prevalent in the Qinghai Tibetan Plateau. The changes in spring, summer and autumn onset were most pronounced in western Eurasia.
“It’s a hot spring so that it essentially becomes summer,” said Amir Sapkota, who studies extreme weather events and human health at University of Maryland and was not involved in the study. “With the earlier and much longer summer, spring gets shorter and shorter, and it starts early, too. Winter suddenly becomes a lot more compressed.”
The team defined the start of summer when temperatures were in the hottest 25 percent during the study period, and summer ended when the temperature fell below that threshold. Winter began when temperatures dipped to the coldest 25 percent of the period. Spring and autumn were the transition periods between the seasons.
Guan said even though his analysis only goes up to 2011, the recent decade is the warmest period on record and the general trend is the same. Other analyses expanded to 2018 and 2019 also showed similar trends in the United States and Australia. In Washington, the average date of its first 90-degree has advanced five days, from May 21 to May 16, over the last century.
Summers are growing longer due to climate change, while winters are dramatically shrinking in the U.S.
The primary driver of these seasonal trends is human-caused warming because of greenhouse gas emissions, Guan’s study showed. The observed changes in seasonal cycles weakened when model simulations were run without the increase of these heat-trapping gases. If emissions do not slow, the seasonal changes will intensify in the coming decades.
The animation shows changes in average start dates and lengths of the four seasons in the Northern Hemisphere mid-latitudes from 1952 to 2011 to 2100. (Wang et al 2020/Geophysical Research Letters/AGU.)
Under the current business-as-usual scenario, projections show summer could last six months by 2100, while winter would be less than two months. Spring and summer will start about one month earlier in 2100 than it did in 2011, and autumn and winter would start a half month later.
But perhaps the most alarming aspect of changing seasonal cycles are the impacts on the environment, animals and human health.
“When you push ecosystems into a regime that we haven’t seen before, you just end up with a ton more uncertainty in every direction,” said Anna Michalak, a climate scientist at the Carnegie Institution for Science. “That’s much more difficult to deal with from a management standpoint.”
much more at: https://www.washingtonpost.com/weather/2021/09/22/longer-northern-hemisphere-summer-climate/
But recently, the seasons have been out of whack. Over the past seven decades, researchers found high summertime temperatures are arriving earlier and lasting longer in the year because of global warming.
This summer was no exception. In parts of California, which saw its hottest summer on record, unusually warm temperatures arrived in May. Shasta Dam posted its third warmest May on record, a harbinger of a record melt season for the glaciers on the summit of Mount Shasta to its north. Sacramento logged its fifth warmest May.
Folsom Lake during a drought in Granite Bay, Calif. on Aug. 27. (David Paul Morris/Bloomberg)
In the Pacific Northwest, a record-breaking heat wave in late June also occurred much earlier than the region is accustomed to. On June 28, Seattle reached 108 degrees and Portland reached 116 degrees.
“The old rule for our area was typically from the Fourth of July on, you could expect some hot weather,” said Michael Brady, an economics professor at Washington State University. “So not only was the level of the temperatures unprecedented, it was also at least a couple of weeks before you would even expect high temperatures.”
Pacific Northwest heat wave was ‘virtually impossible’ without climate change, scientists find
Unusually hot weather also lasted longer than usual in parts of the Lower 48 states as a late-season heat wave scorched the West in the second week of September. Denver hit 99 degrees on Sept. 10, its highest temperature recorded so late in the season. Earlier that week, Death Valley reached 122 degrees, the highest temperature observed so late in the year anywhere on the planet.
As we mark the end of summer and the fall equinox on Wednesday, fall and winter may not offer much reprieve. Research shows summers are expanding while spring, autumn and winter are becoming shorter and warmer with significant impacts for people and the environment.
By late this century, summer could last six months, winter could be less than two
(Pixabay)In April 2018, a sizable snowstorm blanketed several towns in New Jersey in what seemed like a freak occurrence. In March 2012, unusually warm temperatures in Michigan caused vegetation to emerge from dormancy early, but then were subsequently destroyed by freezing weather in April.
As more unusual weather reports popped up over the years, researcher Yuping Guan was inspired to examine how seasonal cycles were changing. He and his colleagues analyzed temperature data from 1952-2011 and found the four seasons no longer occur equally and had irregular onsets.
In the Northern Hemisphere mid-latitudes, the length of summer increased from 78 to 95 days — or about 4.2 days per decade from 1952-2011. Winter contracted from 76 to 73 days, or 2.1 days per decade on average. Spring decreased from 124 to 115 days, and autumn shrank from 87 to 82 days; each shrank about one day per decade. All seasons were warmer. The most obvious seasonal length changes occurred around the Mediterranean and the Tibet Plateau.
Without changes to mitigate global warming, summer could last nearly six months, study finds
Guan wrote in an email that it’s difficult for people to feel the effects of a small rise in global temperature over many decades, but that the changing length of seasons is something “everyone can understand.”
The onsets of all seasons also changed. Spring started 1.6 days earlier each decade, and summer started 2.5 days earlier. Autumn was delayed by 1.7 days per decade, and winter was delayed by 0.5 days. The delayed winter was the most prevalent in the Qinghai Tibetan Plateau. The changes in spring, summer and autumn onset were most pronounced in western Eurasia.
“It’s a hot spring so that it essentially becomes summer,” said Amir Sapkota, who studies extreme weather events and human health at University of Maryland and was not involved in the study. “With the earlier and much longer summer, spring gets shorter and shorter, and it starts early, too. Winter suddenly becomes a lot more compressed.”
The team defined the start of summer when temperatures were in the hottest 25 percent during the study period, and summer ended when the temperature fell below that threshold. Winter began when temperatures dipped to the coldest 25 percent of the period. Spring and autumn were the transition periods between the seasons.
Guan said even though his analysis only goes up to 2011, the recent decade is the warmest period on record and the general trend is the same. Other analyses expanded to 2018 and 2019 also showed similar trends in the United States and Australia. In Washington, the average date of its first 90-degree has advanced five days, from May 21 to May 16, over the last century.
Summers are growing longer due to climate change, while winters are dramatically shrinking in the U.S.
The primary driver of these seasonal trends is human-caused warming because of greenhouse gas emissions, Guan’s study showed. The observed changes in seasonal cycles weakened when model simulations were run without the increase of these heat-trapping gases. If emissions do not slow, the seasonal changes will intensify in the coming decades.
The animation shows changes in average start dates and lengths of the four seasons in the Northern Hemisphere mid-latitudes from 1952 to 2011 to 2100. (Wang et al 2020/Geophysical Research Letters/AGU.)
Under the current business-as-usual scenario, projections show summer could last six months by 2100, while winter would be less than two months. Spring and summer will start about one month earlier in 2100 than it did in 2011, and autumn and winter would start a half month later.
But perhaps the most alarming aspect of changing seasonal cycles are the impacts on the environment, animals and human health.
The impacts of a longer summer, shorter winter
While a longer summer might sound nice for sunbathers, even small seasonal shifts can throw off the balance of our ecosystem from crop production to increased occurrence of mosquito-borne diseases. With the onset of seasons inconsistent recently, predicting and preparing for those environmental changes is difficult.“When you push ecosystems into a regime that we haven’t seen before, you just end up with a ton more uncertainty in every direction,” said Anna Michalak, a climate scientist at the Carnegie Institution for Science. “That’s much more difficult to deal with from a management standpoint.”
much more at: https://www.washingtonpost.com/weather/2021/09/22/longer-northern-hemisphere-summer-climate/
