The summers may stretch for six months in the Northern Hemisphere in the next 80 years if the climate change is not slowed down. A new study published in the Geophysical Research Letters journal highlights that the Mediterranean region and the Tibetan Plateau have experienced the greatest changes to their seasonal cycles. This would have severe impact on agriculture, human health and the environment.
During the 1950s, the researchers noted, the four seasons arrived in a predictable and fairly even pattern in the Northern Hemisphere. However, climate change is causing dramatic and irregular changes to the length and start dates of the seasons. This may become more extreme in the future under a business-as-usual climate scenario, the study noted. "Summers are getting longer and hotter, while winters shorter and warmer due to global warming," said lead author Yuping Guan from the Chinese Academy of Sciences.
The researchers used historical daily climate data from 1952 to 2011 to measure changes in the four seasons' length and onset in the Northern Hemisphere. The start of summer was defined by the onset of temperatures in the hottest 25% during that time period, while winter began with temperatures in the coldest 25%. Established climate change models were then used to predict how seasons will shift in the future.
On average, the summer grew from 78 to 95 days between 1952 to 2011, while winter shrank from 76 to 73 days, the study found. Spring and autumn were affected with the seasonal duration contracting from 124 to 115 days, and 87 to 82 days, respectively. Hence, spring and summer began earlier, while autumn and winter started later.
If these trends continue without any effort to mitigate climate change, the researchers predict that by 2100, winter will last less than two months, and the transitional spring and autumn seasons will shrink further as well.
"Numerous studies have already shown that the changing seasons cause significant environmental and health risks," Guan said. For example, birds are shifting their migration patterns and plants are emerging and flowering at different times, the study stated. These phenological changes can create mismatches between animals and their food sources, disrupting ecological communities.
But it's not just the wild habitat that are under threat. Seasonal changes can also wreak havoc on agriculture, especially when false springs or late snowstorms damage budding plants, the study noted. With longer growing seasons, humans will breathe in more allergy-causing pollen, and disease-carrying mosquitoes can expand their range northward, it said.