This anamoly in nature was spotted by the Earth Resources Technology in Camp Springs, Maryland, after analyzing satellite images showing seasonal changes in vegetation colour across the US from 1982 to 2005.
It was found that in latitudes above 40 degree north, plants came into spring bloom an average of 0.32 days per year earlier over the period. But below 31 degree north, plants bloomed an average of 0.15 days later.
The tipping point, where climate change had no effect, was at 35 degree north. A similar pattern emerged when the records of lilacs flowering each year was examined.
"It's really surprising because studies usually show plants greening earlier," New Scientist quoted Xiaoyang Zhang of Earth Resources Technology as saying. "Nobody had noticed how warming temperatures can delay the green-up," he added.
"I think that some plants need to be exposed to a short cold snap to sprout," said Zhang. "Plants at northern latitudes still get this, but those below 35° north do not, causing them to sprout later as the climate warms," he added.