Climate change – past trends

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

(This is an early draft of an incomplete article. The figures and tables might be used later)

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.”

Wikipedia¹⁴

Surface average atmospheric CO₂ concentration

Source: Le Quéré et al (2018)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 anomalies 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

https://www.climatelevels.org/¹⁰

Global CH₄ levels

https://www.climatelevels.org/¹⁰

Global N₂O levels

https://www.climatelevels.org/¹⁰

Global temperature record

https://www.climatelevels.org/¹⁰

Global O₂ levels

https://www.climatelevels.org/¹⁰

Global mean sea level

https://www.climatelevels.org/¹⁰

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: carbon dioxide CO₂, methane CH₄, & nitrous oxide N₂O

Sources: IPCC (2007)² AR4 WG1, Fig. TS.1 modified, http://www.methanelevels.org/, http://www.n2olevels.org/, https://www.co2.earth/

The figure above is based on a 2007 IPCC figure. The GHG levels were updated for 2018. Feel free to download it: Glacial-interglacial ice core data_IPCC AR4 WG1 Fig. TS.1_modified image.png

Ice core data and modelling: CO₂ & CH₄, Sea level, Climate forcing, and Global surface temperature

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).”

Wikipedia¹²

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

Sea-level rise

(This is an early draft and this section is incomplete)

Global mean sea-level (GMSL) as a function of cumulative carbon emissions

Clark et al (2018)⁶Fig. 1

Converting between GtCO₂ and GtC:

Atomic masses:  C = 12, O = 16, CO₂ = 12 + (2 x 16) = 44 ; 1 GtCO₂ corresponds to 12 / 44 GtC ≈ 0.2727 GtC ; 1 GtC corresponds to 44 / 12 GtCO₂ ≈ 3.667 GtCO₂ ; And a petagram equals a gigatonne: 1 PgCO₂  = 1 GtCO₂ (1 petagram = 10¹⁵ grams = 10⁹ tonnes. Where ‘t’ stands for ‘tonne’ which is a metric ton (= 1,000 kg))

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

Arctic Sea Ice Volume Annual Maximum, Loss, and Ice Remaining at Minimum

Source: Jim Pettit⁸

References:

1. Le Quéré et al (2018) Global Carbon Budget 2017
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. ‘Arctic Sea Ice Volume Annual Maximum, Loss, and Ice Remaining at Minimum’, Jim Pettit, from PIOMAS data
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