Since the 2009 Copenhagen Climate Summit, the world has been aiming to limit global warming to two degrees Celsius above pre-industrial levels.
But amid fears by vulnerable countries that two degrees was not 'safe', the Paris Climate Agreement last year tightened this global goal to 'well below two degrees while pursuing efforts to limit the increase to 1.5 degrees'.
A new report for the Climate Institute has found that this seemingly small difference in global average temperature represents a large addition of energy into the global climate system.
For example, in a world that is two degrees Celsius warmer than pre-industrial levels, the typical annual length of warm spells would be up to 60 days longer than today across northern parts of Australia, and around 20 days longer across central and southern regions. This increase would be reduced by at least 30 per cent if global warming is limited to 1.5 degrees Celsius.
Sea level is also significant. The report says two degrees Celsius will lock in a 'multi-metre' increase in sea levels over centuries—but 1.5 degrees Celsius will lead to 'declining rates of sea level rise' toward the end of this century.