It is almost certain, in our opinion, that the planet will breach the 1.5°C warming limit set by the U.N. in 2015 to avoid dangerous global heating.
The World Meteorological Office are slightly more conservative, suggesting a 66% chance of the limit being breached by 2027.
Those appreciating the rationale of this limit are rightly alarmed. But we should consider one or two aspects of the impending breach:
The final nudge for this particular breach - as there may be others in the future - is the work of natural climate variability. That is to say, we have been led to the edge of the 1.5°C limit by carbon-driven heating, yet a natural process, El Nino, will take us over the edge.
For the last few years, the Pacific Ocean has been in the opposite condition to El Nino, 'La Nina'. Sea surface waters have been cooler than normal, moderating the background human-driven heating, keeping warming to around 1.2°C.
The switch to El Nino in the Pacific, underway now, will remove this effect and add a couple of tenths of a °C in the immediate couple of years. Combined with the increasing carbon-warming we'll topple over the limit.
Is it Really a breach - Paris style?
Not all 1.5°C warmings are equal. Reminded of this in a recent conversation, with an IPCC Lead Author, the actual United Nations Paris Agreement refers to a 1.5°C limit of 'human-driven' warming. In this sense, then, the imminent breach does not qualify since the final couple of tenths of a degree can be ascribed to a natural phenomenon.
An accurate way to discern if a 1.5°C rise is indeed human-driven is to take a 30-year average of global temperatures. A 30-year block is sufficient to 'iron out' the largest natural warming/cooling processes, leaving a robust indication of the background carbon-driven warming.
A Temporary Breach?
One possibility, therefore, is that we are taken over the 1.5°C limit by El Nino for a couple of years and return to a sub-1.5°C status as El Nino wanes back to La Nina. In honesty, in our opinion, and given the present levels of continuing CO2 emissions, I think this is unlikely. Within a few years the carbon-driven warming may well be sufficient to sustain the breach, irrespective of the influence of El Nino & La Nina.
Still in The Fight
A loss of the 1.5°C limit due to carbon-emissions will be a tough pill to swallow and in honesty most reasonable climate scientists know this is coming and have done for the last four or so years. The cascade of severe weather events, land-surface transformations, and socio-economic instabilities that are unfolding are testament alone.
Yet there is a wider and more important war being fought. And victory can still be achieved. Establishing 1.5°C as a warming limit was done so because, compared to the planetary changes which commence at 2.0°C, the impacts at 1.5°C of warming are deemed less 'dangerous'. A human-driven (i.e. a sustained phase of 30-or so years) warming of 2.0°C or more leads to catalogue of disastrous changes, some of which will be irreversible over the course of hundreds, if not thousands, of years.
It is territory we do not want to flirt with - a real life experiment on our planet that would go badly wrong in serious ways.
Our current emission levels will lead to a human-driven warming of around 2.7°C by 2100. We are on red alert, code red, right now.
The good news is that immediate action and change can still divert us to a sub-2.0°C future. The fight is now and we have a window to make the changes needed.