Summers in the northern hemisphere can last almost six months until the year 2100 if global warming remains uncontrolled, according to a recent study that examined how climate change is affecting the pattern and duration of Earth’s seasons.
The study, published last month in the journal Geophysical Research Letters, found that climate change is making summers hotter and longer, while decreasing the other three seasons. Scientists say the irregularities can have a number of serious implications, affecting human health and agriculture for the environment.
“This is the biological clock of all living things,” said the study’s lead author, Yuping Guan, a physical oceanographer at the State Academy of Tropical Oceanography at the Chinese Academy of Sciences. “People argue about raising the temperature by 2 or 3 degrees, but global warming changing seasons is something that everyone can understand.”
Guan and his colleagues combed daily weather data from 1952 to 2011 to locate the beginning and end of each season in the northern hemisphere. They found that, over the nearly 60-year period, summers were becoming, on average, 78 to 95 days longer – a difference of about three months.
Winters, on average, have shortened from 76 to 73 days, and the spring and autumn seasons have decreased similarly. On average, the spring seasons decreased from 124 days to 115 days, and autumns shortened from 87 days to 82 days.
Scientists used the findings to build a model to project how the seasons could change in the future. They found that if the pace of climate change continues to be mitigated, summers in the northern hemisphere can last for almost six months, while winters can last for less than two months.
In their study, Guan and his colleagues measured the beginning of summer based on the beginning of temperatures in the 25% warmest during that period. Winter was defined as the start of temperatures in the coldest 25%, they said.
Previous research has shown that climate change is having a profound impact on the planet’s seasons – making summers hotter and longer and winters shorter and hotter – but Guan said he was surprised by the dramatic results of his team’s future projections .
“We first looked at 2050 and then we calculated the move to 2100, and that was a large number,” said Guan. “For human well-being, I really hoped that these results were wrong.”
Changes in Earth stations pose risks to the environment and human health. Warmer and longer summers, for example, mean that mosquitoes and other disease-carrying pests can expand their reach and persist in areas where they are not normally found.
“You could get to a point where insects like malaria mosquitoes, which are normally kept out of high altitude areas because they cannot survive overnight, could survive longer and at higher altitudes,” said Scott Sheridan, climate scientist at Kent State University in Ohio, who did not participate in the study.
And because seasons dictate the life cycles of plants and animals, climate change can hinder the species’ ability to adapt.
“If the seasons start to change, everything is not going to change perfectly in sync,” said Sheridan. “If we take an example of flowers that come out of the ground, these flowers may appear, but the bees are not yet there to pollinate or have already passed the peak.”
Climate change is also making seasons more “fickle,” said Sheridan, which could have far-reaching impacts on agricultural production. In the United States, for example, a “false spring” in March 2012, characterized by an exceptionally warm climate, took vegetation out of dormancy weeks ahead of schedule, before temperatures dropped again in April.
“It all started to work out thinking that early summer had come,” said Sheridan. “In the state of Michigan, large amounts of the cherry crop were lost as a result. Similar things happened in the south with the peach crop.”
In fact, scientists are eager to understand precisely how climate change will affect seasons due to the potential impact on food production.
Weston Anderson, a postdoctoral researcher at the International Research Institute for Climate and Society at Columbia University, studies the effect of climate variability on agriculture and food security. Global warming affects not only where certain crops can grow and when, but also how much they thrive.
“One of the main concerns is how the warming temperatures will affect the development time of crops,” said Anderson, who was not involved in the recent study. “This means how quickly the crops mature and, as a result, how much the crops are affected.”
While food production problems have global side effects, the Mediterranean region is an area that appears to be particularly susceptible to global warming, said Anderson.
“We are already seeing in the Mediterranean that temperatures are rising and the region is becoming increasingly arid, less suitable for wheat planting,” he said, adding that places that are already semi-arid are also vulnerable.
Sheridan said the study’s findings help to illustrate the severity of climate change, illustrating how interconnected humans, other animals, plants and the environment are.
“Changing seasons can do a lot more damage than you think when you realize all the systems that are adjusted to the time of the seasons,” he said.