Climate change – past trends

View from International Space Station
Photograph: ISS/Nasa (downloaded 24 Aug. 2018)

Excess greenhouse gas emissions – a pathway out of the Holocene

“The Holocene14 has seen the growth and impacts of the human species worldwide, including all of its written history, development of major civilizations, and overall significant transition toward urban living in the present.”

Atmospheric CO2 concentration

Source: Friedlingstein et al (2022)1, Fig. 1

Holocene up to the present day: ‘temperature anomaly’

Sources: Hansen et al (2017)3Fig. 3b & Fig. 2, Spratt (2017)9 modified

Temperature anomaly relative to the years 1880-1920
  • Centenially-smoothed Holocene temperatures (blue)
  • 11-year mean modern temperatures (red)

Global surface temperature relative to 1880-1920

Source: Hansen et al (2017)3Fig. 2

Global CO2 levels

Global CH4 levels

Global N2O levels

Global temperature anomaly relative to the years 1951-1980
“Base period for temperature anomaly: 1951-1980 as per source NASA GISS GLOBAL Land-Ocean Temperature Index” Data source

Global O2 levels

Global mean sea level

Possible future pathways of the climate against the background of the typical glacial–interglacial cycles

Source: Steffen et al (2018)5 Fig. 1

Stability landscape showing the pathway of the Earth System out of the Holocene

Source: Steffen et al (2018)5 Fig. 2

Ice core data and CO2 levels over geologic time

Glacial-interglacial ice core data and recent GHG levels (2007). Carbon dioxide CO2 (red), methane CH4 (blue), & nitrous oxide N2O (green)

Sources: IPCC (2007)2 AR4 WG1, Fig. TS.1 modified
The figure above is based on a 2007 IPCC figure.

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)4Fig. 5 & 6

Model simulations and reconstructions from measured data for the last 3 million years

Source: Willeit et al (2019)11 Fig. 2b, 2d, & 2f

“Our results also support the notion that the current CO2 concentration of more than 400 ppm is unprecedented over at least the past 3 Ma and that global temperature did not exceed the preindustrial value by more than 2°C during the Quaternary. In the context of future climate change, this implies that a failure in substantially reducing CO2 emissions to comply with the Paris Agreement target of limiting global warming well below 2°C will not only bring Earth’s climate away from Holocene-like conditions but also push it beyond climatic conditions experienced during the entire current geological period.”
Willeit et al (2019)11 Pg. 5

The Quaternary Period covers the last 2.58 million years, up to the present. “The Quaternary Period is divided into two epochs: the Pleistocene (2.588 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today).”

CO2 over 420 million years

Foster, Royer & Lunt (2017)13 Fig. 4

“Unabated fossil fuel use therefore has the potential to push the climate system into a state that has not been seen on Earth in at least the last 420 Myrs”
Foster, Royer & Lunt (2017)13 Pg. 5

Historical sea-levels and future projections

Projected global mean sea level rise under different SSP scenarios

Source: IPCC Sixth Assessment Report WG1 (2021)8 Ch. 9 Fig. 9.27

Global Mean Sea Level (GMSL) rise projections as a function of peak global surface air temperature

Source: IPCC Sixth Assessment Report WG1 (2021)8 Ch. 9 Fig. 9.30

Global mean sea level (GMSL) projections and commitments for exceedance of five global warming levels

Source: IPCC Sixth Assessment Report WG1 (2021)8 Ch. 9 Table 9.10

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)8 Ch. 9 Table 9.6

Estimates for historical atmospheric CO2 levels and coinciding sea levels

Source: Foster & Rohling (2013)7Fig. 3
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). “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”.
Foster & Rohling (2013)7Pg. 4

  1. Friedlingstein et al (2022) Global Carbon Budget 2022
  2. IPCC (2007) AR4 WG1, Figure TS.1
  3. Hansen et al (2017) Young people’s burden: requirement of negative CO2 emissions
  4. Hansen et al (2013) Climate sensitivity, sea level, and atmospheric carbon dioxide
  5. Steffen et al (2018) Trajectories of the Earth System in the Anthropocene
  6. Clark et al (2018) Sea-level commitment as a gauge for climate policy
  7. Foster & Rohling (2013) Relationship between sea level and climate forcing by CO2 on geological timescales
  8. IPCC Sixth Assessment Report WG1 (2021) Ch. 9
  9. ‘Paris 1.5-2°C target far from safe, say world-leading scientists’, David Spratt, Renew Economy, 27 July 2017
  10. Climate levels graphs: A project of the 2 Degrees Institute
  11. Willeit et al (2019) Mid-Pleistocene transition in glacial cycles explained by declining CO2 and regolith removal
  12. Wikipedia, ‘Quaternary’, accessed 10 May 2019
  13. Foster, Royer & Lunt (2017) Future climate forcing potentially without precedent in the last 420 million years
  14. Wikipedia, ‘Holocene’, accessed 12 May 2019