Such a rise would have a devastating impact on life on Earth. It would place billions of people at risk from extreme temperatures, flooding, regional drought, and food shortages, researchers said.
The study conducted by researchers at the University of Edinburgh in UK calculated the likely effect of increasing atmospheric levels of greenhouse gases above pre-industrialisation amounts.
It found that if emissions continue to grow at current rates, with no significant action taken by society, then by 2100 global land temperatures will have increased by 7.9 degrees Celsius compared with 1750.
It also breaches the United Nations' safe limit of two degrees Celsius, beyond which the UN says dangerous climate change can be expected, researchers said.
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Researchers first created a simple algorithm to determine the key factors shaping climate change and then estimated their likely impact on the world's land and ocean temperatures.
The study was based on historical temperatures and emissions data. It accounted for atmospheric pollution effects that have been cooling Earth by reflecting sunlight into space, and for the slow response time of the ocean.
The findings were published in the journal Earth and Environmental Transactions of the Royal Society of Edinburgh.