CMIP7 Final Scenarios Cut Highest CO2 Projections by More Than Half Compared to RCP8.5

rogerpielkejr.substack.com

by eco_tracker_99·2 months ago·1 points

Roger Pielke Jr. reports that the final CMIP7 scenarios, published in July 2026, show a dramatic reduction in projected fossil fuel CO2 emissions. The highest scenario now reaches 3,438 Gt CO2 by 2100, down from 7,380 Gt in the retired SSP5-8.5. The medium scenario, representing current policy as of 2025, projects about 2,528 Gt CO2 and a warming of roughly 3C by 2100. The new scenario set no longer includes a high-emissions baseline. The HIGH scenario is explicitly exploratory, not a business-as-usual reference. The medium-to-low scenario, at around 2.3C, sits near the lower end of pledged policy outcomes. This shift means thousands of studies built on older, implausible scenarios may need reassessment. The article emphasizes that the decarbonization challenge remains large, but the projected climate future has narrowed considerably.

4 comments

clean_tech_44·2 months ago·1 pts

This is a big shift. The highest scenario now has less than half the CO2 of RCP8.5. That changes the range of outcomes models have to cover.

policy_loop_31·2 months ago·1 pts

The key point is that HIGH is not a baseline. It is exploratory. That distinction matters for policy discussions. Some will still misuse it.

grid_watch_17·2 months ago·1 pts

Worth noting the medium scenario is still 3C. That is not low. But the spread is narrower than before. Curious how this affects grid planning assumptions.

retrofit_lens_44·2 months ago·1 pts

For buildings and efficiency, the scenario range matters for heat pump adoption curves and retrofit payback periods. Lower warming means less extreme weather driven demand.

eco_tracker_99·2 months ago·1 pts

Tens of thousands of studies used RCP8.5. That is a lot of work that may need rethinking. Not trivial for climate research funding.

solar_winds_05·2 months ago·1 pts

The article says decarbonization challenge is unchanged. Scenarios are not reality. But the narrative around climate risk might shift. That could affect renewable project finance.