Changing Lengths of the Four Seasons by Global Warming

TLDR: In this paper, the authors found that summer in the Northern Hemisphere midlatitudes has lengthened, whereas winter has shortened, owing to shifts in their onsets and withdrawals, accompanied by shorter spring and autumn.

Abstract: How long will the four seasons be by 2100? Increasing evidence suggests that the length of a single season or in regional scales has changed under global warming, but a hemispherical-scale response of the four seasons in the past and future remains unknown. We find that summer in the Northern Hemisphere midlatitudes has lengthened, whereas winter has shortened, owing to shifts in their onsets and withdrawals, accompanied by shorter spring and autumn. Such changes in lengths and onsets can be mainly attributed to greenhouse-warming. Even if the current warming rate does not accelerate, changes in seasons will still be exacerbated in the future. Under the business-as-usual scenario, summer is projected to last nearly half a year, but winter less than 2 months by 2100. The changing seasonal clock signifies disturbed agriculture seasons and rhythm of species activities, more frequent heat waves, storms and wildfires, amounting to increased risks to humanity. Plain Language Summary A series of phenomena such as early flowering of plants and early migratory birds are suggesting that the traditional four seasons may have changed. We focus on how the four seasons changed during 1952-2011 and will change by the end of this century in the warming Northern Hemisphere midlatitudes. We find that lengths and start dates of the four seasons have changed, and the changes will be amplified in the future. Over the period of 1952-2011, the length of summer increased from 78 to 95 days and that of spring, autumn and winter decreased from 124 to 115,87 to 82, and 76 to 73 days, respectively. In addition, summer is projected to last nearly half a year, but winter less than 2 months by 2100. Such changes can trigger a chain of reactions in agriculture, policy-making for agricultural management and disaster prevention requires adjustment accordingly. The seasonal-related topics involving ecology, the ocean and the atmosphere also need to be revisited.