Thread by @_richardblack

THREAD: Sparked by Frans @TimmermansEU's remarks that #COP27 could kill off the #ParisAgreement 1.5 Celsius temperature target

https://twitter.com/TimmermansEU/status/1593871686851518465

, a short thread on some realities of 1.5°C

This is also a nod to all those lining up to pontificate that '1.5°C is dead', particularly scientists who make no attempt to clarify that that what they're saying is just their opinion, not fact

Firstly let's look at the #ParisAgreement's wording - to 'hold' warming 'well below 2°C' while 'making efforts' to keep it to 1.5°C. There is no time limit on that 'making efforts'. Governments did not pledge to make efforts until warming exceeds 1.5°C and then stop

The best way to view this is as a single target, 1.5°C. Warming may temporarily overshoot this a bit and then fall back, but it never stops being the target

Secondly, a bit of science. 1) the precise extent of emissions that will result in a certain level of warming can't be predicted precisely. There are ranges and probabilities. What actually happens can only be known in retrospect

2) the extent of global warming to date also has a range, 0.8-1.3°C. Science is always updating this and in fact the estimated range changed between AR5 and AR6. Science will surely narrow the range further, toward either the low or high end

3) temperatures are affected by annual variability and natural cycles of several years

Putting those three things together, it's clear that there won't be a moment when 1.5°C is declared 'passed'. If emissions don't fall fast enough, we would see a gradually increasing probability that we have passed it. But (see earlier) getting back to it remains the target

That's the science done. Now there's the morality

Remember how the 1.5°C target got into the #ParisAgreement: because groups of small island states, the poorest countries in the world, and those most vulnerable to climate impacts insisted that it should

It's not for a politician or scientist in Europe or North America to declare '1.5°C is out of reach'. To them this can be an academic or political point. For the islanders, for subsistence farmers in Africa, this is about survival. Morally, they own the target

There's a third issue. As scientist @JamesGDyke recently discovered

https://twitter.com/JamesGDyke/status/1593154408602554368

, arguing that 1.5°C is dead hands a piece of ammunition to those who want it to be dead; because if something can't be done, why try?

Most fundamentally though, '1.5°C is dead' is a sterile discussion. It is however undeniably true that the faster countries cut fossil fuel burning and protect their forests and ecosystems, the lower the eventual extent of global warming will be

Rolling out clean energy and nature protection as quickly as possible gives the best chance of not overshooting 1.5°C, and will keep any overshoot to the smallest extent possible

And in the real world, this is happening at an astounding rate. Exponential 20% yr-on-yr growth for wind and solar generation, EVs accelerating faster than anyone thought possible, more attention and money coming into forest protection

Fast enough to 'keep 1.5°C alive'? I don't know whether it's fast enough to avoid overshoot - as of now, no-one can know that. The @IPCC_CH is fairly clear that quick and deep cuts in emissions are needed to have a decent chance of avoiding it

But we're in a grey zone, not a black and white zone. The quicker the emission cuts, the lighter the grey; the more the defeatism, the darker the grey

With determination for progress and a bit of luck with climate sensitivity, light grey can become white. The implications should be obvious