If you've noticed summers getting hotter and longer, you're not alone: Climate scientists have had their eyes on an uncomfortable warming trend for decades. 

But how much have the seasons changed - and what could be ahead?

A new analysis by Chinese researchers has an unnerving prediction: If humans don't make any effort to lessen climate change, summer could last nearly six months by 2100. The study, published in Geophysical Research Letters, used temperature data to track seasonal changes in the Northern Hemisphere between 1952 and 2011. The researchers defined the start of winter as the onset of the coldest 25 percent of temperatures and summer as the onset of the hottest 25 percent.

On average, winter waned from 76 to 73 days, spring shrank from 124 to 115 days, and fall fell from 87 to 82 days.

But summer ballooned over the 59-year period, growing from 78 days to a whopping 95.

Then the researchers used the data to project what might be to come in scenarios with different climate change curbs. The worst-case scenario model saw winter shrinking down to less than two months a year and summer lasting nearly a half-year.

That could wreak ecological havoc, disrupting agriculture, causing species' life cycles and migrations to fall out of sync, and increasing the risk of drought and severe fires. Humans would suffer, too: Warming summers are already projected to cause additional deaths due to heat stress, malnutrition and malaria, and longer growing seasons mean more seasonal allergies because of pollen.

Fortunately, the worst-case projection isn't inevitable. If humans continue to mitigate climate change and manage to curb carbon emissions, summer probably won't get as long.

The data is sobering, however - and shows that the seasons have already shifted. "Even if the current warming rate does not accelerate, changes in seasons will still be exacerbated in the future," the researchers write. Human-caused climate change has already altered our world, pushing us closer to a seemingly endless summer.