A study published in the journal Nature revealed that tropical forests would become so hot that some kinds of leaves would no longer be able to conduct photosynthesis, reported The Guardian.

The photosynthesis process in tropical trees begins to fail at about 46.7C on average. The research suggests that the forests were near reaching dangerous temperatures sooner than expected.

The researchers used high-resolution data collected from NASA’s thermal imaging instruments on the International Space Station and ground base experiments in tropical forests across the world. They found that nearly 0.01 per cent of all leaves were already exposed to temperatures beyond limits.

The study also found that once the global temperature reaches 3.9 C, these forests might experience mass leaf damage.

Chris Doughty, an associate professor of ecoinformatics at Northern Arizona University and the lead researcher of the study said: “Warming leaves, even if now in low numbers, act as a “canary in a coalmine for tropical ecosystems.”

“We were really surprised that when we warmed leaves by 2, 3 or 4C, the highest leaf temperature increased by 8C. This shows a concerning nonlinear feedback that we were not expecting,” said Doughty.

“If we adopt a do-nothing response to climate change and tropical forest air temperatures increase by greater than 4C, there could be massive leaf death, possible tree mortality and species turnover across all tropical forests,” he added.

In terms of global impact, “the photosynthetic response would be the tip of the iceberg in terms of effects – reduced carbon uptake, likely increased mortality and even triggering possible transitions from forest to savannah”, said Mat Disney, a professor of remote sensing at University College London.