What does the 1.5-degree limit mean?

Is it me, or does COP26 seem to be more relevant than all the other 25 COPs that have taken place?  And whilst there have been discussions of the 1.5-degree limit over recent years, I certainly can’t recall there being just this much focus on it.

So, what, exactly, does the 1.5 degrees refer to?

Historically at previous COPs, it had been generally agreed that an increase in global warming of greater than 2.0 degrees would be devastating.  However, at COP21 in Paris there was some concern that this limit may be too high.  It was agreed that the Intergovernmental Panel on Climate Change (IPCC) would provide a special report in on ‘the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways.’ 

IPCC’s report brought the concerns home to Governments around the world, and the intent to remain within this 1.5-degree increase was accepted, by most, in 2018, as a very bad thing. The concern, put simply, is that if global warming exceeds this figure land mass would be eroded through rising sea levels, wildfires will destroy property and further destroy the environment, that storms, droughts, floods, and other natural disasters would cause untold suffering, and there would be significant human movements as a result.

Currently various scientific bodies, including the IPCC, estimate that the planet is at 1.1 or 1.2 degrees along this scale.  Importantly, since pre-industrial times, this temperature has largely been increasing in a straight line.  It is easy to predict, then, that 1.5 degrees will be reached by the year 2030 if no action is taken. That will soon be in eight short years.

Hence the focus.  Hence the investments in ‘clean’ energy and the like.  Hence all the net zero carbon emissions targets.