How do we know CO2 levels?
What is the base scenario?
source: Climate Change 2023 syntehsis report.
Observed impacts to date.
It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s (
p. 48 contains a graphic detailing how, in particular, agriculutral impacts (droughts) is unevenly distributed. Evapotrapiration?
- The most vulnerable have been disproportionately affected.
How these might progress to the future.
If the ‘emission gap’ is not reduced, global GHG emissions in 2030 consistent with NDCs announced prior to COP26 make it likely that warming will exceed 1.5°C during the 21st century, while limiting warming to 2°C (>67%) would imply an unprecedented acceleration of mitigation efforts during 2030–2050 (medium confidence)
This ‘emissions gap’ is what we will emit, vs what we ‘should’ or have to emit for certain scenarios.
NDC’s?? National declared commitments?
There’s also an implementation gap where projected global emissions implied by policies for 2030 are around, 50-60 Gt/CO2 whereas the scenarios imply this should be about 4-6 Gt lower.