Why One and Half a Degree is so important?

The difference between day and night temperatures could be more than 20 deg C. So what is so ‘special’ about the Special Report by Intergovernmental Panel on Global Warming of 1.5 °C (SR15)? Rajendra Shende explains the extraordinary alarm raised by the report for the humanity. The report also tells categorically what actions are needed to limit the rise to 1.5 deg C .