Table of Contents
Excess greenhouse gas emissions
Atmospheric CO2 concentration
Source: Friedlingstein et al (2025) Global Carbon Budget 2024, Figure 1
Global CO2 levels
https://www.climatelevels.org/
Global CH4 levels
https://www.climatelevels.org/
Global N2O levels
https://www.climatelevels.org/
Global temperature anomaly relative to the years 1951-1980
https://www.climatelevels.org/
Global mean sea level
https://www.climatelevels.org/
Possible future pathways of the climate against the background of the typical glacial–interglacial cycles
Source: Steffen et al (2018) Trajectories of the Earth System in the Anthropocene, Figure 1
Stability landscape showing the pathway of the Earth System out of the Holocene
Source: Steffen et al (2018) Trajectories of the Earth System in the Anthropocene, Figure 2
We can decarbonise and we can protect the biosphere—to move back to the ‘stabilised Earth’ sweet spot.
Atmospheric well-mixed greenhouse gas (WMGHG) concentrations from ice cores
Source: IPCC (2021) AR6 WGI, Chapter 2, Figure 2.4
Ice core data and modelling: CO2 & CH4, sea level, climate forcing, and global mean surface temperature anomaly (over the last 800,000 years)
Source: Hansen et al (2013) Climate sensitivity, sea level, and atmospheric carbon dioxide, Figures 5 & 6
Atmospheric CO2 concentration and global surface temperature change during the last 60 million years and projections for the next 300 years
Source: IPCC (2021) AR6 WGI TS, Figure TS.1
Past and future changes in concentration of atmospheric carbon dioxide and global mean temperature
Source: Clark et al (2016) Figure 1
Historical sea-levels and future projections
Projected sea level rise during our lifetimes might seem trivial, but global commitments over multiple centuries and millennia are surprisingly large—this is highlighted in the consensus-based IPCC reports.
Past and future changes in global mean sea level
Source: Clark et al (2016) Figure 2
Observed and projected global mean sea level change and its impacts, and time scales of coastal risk management
Source: IPCC (2023) AR6 Synthesis Report Figure 3.4
Projected global mean sea level rise under different SSP scenarios
Source: IPCC Sixth Assessment Report WG1 (2021) Chapter 9, Figure 9.27
Global mean sea level (GMSL) projections and commitments for exceedance of five global warming levels
Source: IPCC Sixth Assessment Report WG1 (2021) Ch. 9 Table 9.10
“In the longer term, sea level is committed to rise for centuries to millennia due to continuing deep-ocean warming and ice-sheet melt and will remain elevated for thousands of years (high confidence).”
Source: IPCC (2021) AR6 WGI Summary for Policymakers, B.5.4
Global surface temperature change 10 and 100 years after a one-year pulse of present-day emissions
Source: IPCC (2021) AR6 WGI TS, Figure TS.20
How Long Does CO2 Stay in the Atmosphere?
Source: IPCC (2013) AR5 WGI Chapter 6, Box 6.1, Figure 1, pg. 473
Global Mean Sea Level (GMSL) change on 100- (blue), 2,000- (green) and 10,000-year (magenta) time scales as a function of global surface temperature, relative to 1850–1900
Source: IPCC (2021) AR6 WGI TS, Box TS.4, Figure 1b
Global mean sea level (GMSL) as a function of cumulative carbon emissions
Source: Clark et al (2018) Sea-level commitment as a gauge for climate policy, Figure 1
Global Mean Sea Level (GMSL) rise projections as a function of peak global surface air temperature
Source: IPCC Sixth Assessment Report WGI (2021) Chapter 9, Figure 9.30
Reference ranges of age, global mean surface temperature (GMST), atmospheric carbon dioxide (CO2) concentration, and global mean sea level (GMSL)
Source: IPCC Sixth Assessment Report WG1 (2021) Chapter 9, Table 9.6
“Projections of multi-millennial global mean sea level rise are consistent with reconstructed levels during past warm climate periods: likely 5–10 m higher than today around 125,000 years ago, when global temperatures were very likely 0.5°C–1.5°C higher than 1850–1900; and very likely 5–25 m higher roughly 3 million years ago, when global temperatures were 2.5°C–4°C higher (medium confidence).”
Source: IPCC (2021) AR6 WGI Summary for Policymakers, B.5.4
Estimates for historical atmospheric CO2 levels and coinciding sea levels
Source: Foster & Rohling (2013) Relationship between sea level and climate forcing by CO2 on geological timescales, Figures 3a & 3b
The “dotted lines denote the preindustrial conditions of 0 m and 280 ppm CO2. The horizontal orange line shows +14 m, which is the sea-level rise associated with the total melting of WAIS and GrIS” (the Western Antarctic Ice Sheet and the Greenland Ice Sheet).
Source: Foster & Rohling (2013)
“During the Eocene, when CO2 levels were higher than 1,000 ppm, sea level was 60–70 m higher than today, reflecting the absence of any of the major ice sheets that currently reside at high latitudes”
Source: Foster & Rohling (2013)
We can decarbonise and move back to the left on this graph!
Sources for this post:
- Clark et al (2016) Consequences of twenty-first-century policy for multi-millennial climate and sea-level change
- Clark et al (2018) Sea-level commitment as a gauge for climate policy
- Climate levels graphs: a project of the 2 Degrees Institute
- Foster & Rohling (2013) Relationship between sea level and climate forcing by CO2 on geological timescales
- Friedlingstein et al (2025) Global Carbon Budget 2024
- Hansen et al (2013) Climate sensitivity, sea level, and atmospheric carbon dioxide
- IPCC (2013) AR5 WGI, Chapter 6, Carbon and Other Biogeochemical Cycles (pdf)
- IPCC (2021) AR6 WGI, Technical Summary
- IPCC (2021) AR6 WGI, Chapter 2, Changing State of the Climate System
- IPCC (2021) AR6 WGI, Chapter 9, Ocean, Cryosphere and Sea Level Change
- IPCC (2023) AR6 Climate Change 2023 Synthesis Report, Section 3, Long-Term Climate and Development Futures
- Steffen et al (2018) Trajectories of the Earth System in the Anthropocene
Featured image: View from International Space Station
Photograph: ISS/Nasa (downloaded 24 Aug. 2018) https://www.theguardian.com/environment/2017/aug/18/climate-scientist-clouds-climate-change-interview-kate-marvel
