Summers Could Be Six Months Long In The Northern Hemisphere By 2100, Scientists Warn

Lengthy heatwaves could become increasingly frequent. Image: Marian Weyo/Shutterstock.com

As climate change accelerates and global temperatures continue to rise, shifts in the onset of the seasons could bring about disastrous consequences for agriculture, ecology, and human health, according to a new study in the journal Geophysical Research Letters. Based on their analysis, the authors predict that if nothing is done to curb greenhouse gas emissions, then summers could reach half a year in length by the end of this century, with winter lasting less than two months.

The researchers studied changes in the length of the seasons by looking at historical climate data from 1952 to 2011 across the Northern Hemisphere. For each year, they identified the onset of summer by calculating the period with the highest 25 percent of temperatures, while the period with the lowest 25 percent of temperatures was defined as winter.

Across the study period, summers grew in length from 78 days to 95 days, while all other seasons diminished. From 1952 to 2011, winters receded from 76 days to 73 days, autumn shrank from 87 days to 82 days, and spring contracted from a length of 124 days to 115 days.

“Summers are getting longer and hotter while winters shorter and warmer due to global warming,” explained study author Yuping Guan in a statement, before adding that "numerous studies have already shown that the changing seasons cause significant environmental and health risks." For example, longer summers will likely bring about an extended pollen season, which could exacerbate allergies.

While these shifts represent the average across the Northern Hemisphere, certain regions experienced particularly drastic changes. According to the study authors, this trend towards longer summers was most pronounced in both the Mediterranean and the Tibetan Plateau.

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Changes in average start dates and lengths of the four seasons in the Northern Hemisphere mid-latitudes for 1952, 2011 and 2100. Credit: Wang et al 2020/Geophysical Research Letters/AGU.

As a next step, the team used a series of established climate models in order to predict how things might progress depending on how much effort we put into curbing climate change. Results showed that under the "business-as-usual scenario” – which entails no change in our greenhouse gas emissions – “spring and summer will start about a month earlier than 2011 by the end of the century.”

To compound this, “autumn and winter [will] start about half a month later, which [will] result in nearly half a year of summer and less than two months of winter in 2100.”

Should this situation come to pass, the consequences are likely to be far-reaching. For one thing, we’d see a dramatic increase in droughts, wildfires, and other disasters resulting from prolonged heatwaves. Meanwhile, shorter and warmer winters could lead to an increase in the frequency and intensity of storms, with the potential to cause considerable loss of human life.

A change in the onset of seasons would also wreak havoc upon agriculture, as crops would sprout, flower and seed at the wrong times of the year. Similarly, ecological systems may well collapse if animals and plants fall out of sync with each other’s annual cycles.

Fortunately, initiatives to prevent this scenario are underway, with a global agreement in place to try and keep temperatures within two degrees Celsius above pre-industrial levels. Studies like this really bring home just how much is riding on the success of this pledge.

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