Autumn is Starting Later in the Year, Spring Starting Earlier, New Vegetation Study Suggests

New research from the University of Southampton suggests that the timing of the arrival of spring and autumn is changing in the Northern Hemisphere.

Autumn is taking place later in the year and spring is starting slightly earlier, the researchers report.

"There is much speculation about whether our seasons are changing and if so, whether this is linked to climate change," lead study author Peter Atkinson, a professor of geology at University of Southampton, said in a statement. "Our study is another significant piece in the puzzle, which may ultimately answer this question."

Atkinson, along with Southampton colleagues and a team from the Department of Remote Sensing at Birla Institute of Technology in India, published their work in the journal Remote Sensing of the Environment.

The researchers used satellites imagery examine 25 years worth of vegetation data in the North Hemisphere. Working with data collected between 1982 and 2006, the Atkinson and his collaborators were able to measure seasonal changes in vegetation, marked in the data as "greenness" of the land.

By examining vegetation greenness in detail, the researchers can identify the growth cycle and identify physical changes that are marked by the onset of seasons such as leaf cover, color and growth.

Data from grasslands, shrublands, cropland and a variety of forest types were included in the analysis. A mixture of land that has been developed by humans and land left untouched was included in the analysis of overall greenness.

For broad-leaved deciduous and needleleaved deciduous forests, the seasonal changes were most pronounced, the researchers found. In these forests, they documented Autumn occurring significantly later. The delayed arrival of autumn was generally more pronounced than the arrival of an earlier spring, the researchers reported, although they noted that there is evidence across all vegetation groups that spring is occurring slightly earlier.

"Previous studies have reported trends in the start of Spring and end of Autumn, but we have studied a longer time period and controlled for forest loss and vegetation type, making our study more rigorous and with a greater degree of accuracy," Atkinson said. "Our research shows that even when we control for land cover changes across the globe a changing climate is significantly altering the vegetation growth cycles for certain types of vegetation. Such changes may have consequences for the sustainability of the plants themselves, as well as species which depend on them, and ultimately the climate through changes to the carbon cycle."