Thread by @Peters_Glen

The largest update to ocean temperatures since 2011 leads to a 0.1°C upward revision (over oceans), which translates to a ~0.06°C increase of global temperatures.

Does this matter for 1.5°C? Does it effect 'carbon budgets'?

1/

carbonbrief.org/analysis-major…

A change of 0.06°C sounds small, but translates to ~130GtCO₂ (~3 years of emissions). This is significant when 1.5°C is so close.

If we assume 1.5°C is an absolute change from preindustrial, then carbon budgets will now be ~130GtCO₂ smaller.

2/

What about if 1.5°C is a relative change from today? Then a 0.06°C increase is like changing the target to 1.56°C. The change is "just a labelling exercise & doesn’t affect the remaining budget at all".

Which is fine if we accept the relative 0.5°C decreases every year...

3/

Or we could take the SR15 approach that "every degree matters", & by implication we should keep the temperature increase as small as possible to reduce risk.

Again, this is fine (& I support), but does it shift from a target to cost-benefit thinking?

4/

Shifting away from an absolute target to a relative target or "as much as possible" target could be a slippery slope. Each marginal increase in temperature & impact will be compared against the marginal effort to reduce emissions. This is what plays out in reality anyway...
5/

Either way, we will be repeating this discussion for decades, as each new day will bring new data on ECS/TCRE, non-CO₂, climate feedbacks, cumulative CO₂, temperature estimates, definitions, etc, & the remaining carbon budget will go up & down like a yo-yo.
6/

There will be esoteric discussions about definitions, intentions, missed targets, blame, etc, creating a sense of uncertainty, & meanwhile the Saudi Arabia's of the world will have endless material to distract climate meetings (as they are doing now).
7/

Many, particularly from a political science perspective, have raised the challenges of targets, & perhaps we are seeing that play out? The targets need to be quickly translated into actionable items.

Two examples:
nature.com/news/climate-p…
theguardian.com/science/politi…
8/

The Paris Agreement Article 2 was rather vague on the target (basically, it says somewhere between 1.5°C & 2°C, but we are not on track so raise ambition), while science has been very good at focusing on targets (e.g., below 1.5°C, 66% below 2°C). 🤔 9/9