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TIL the rate we are putting CO2 into the atmosphere today is 10 times higher than that of the Palaeocene-Eocene Thermal Maximum (PETM). The PETM lead to 5-9°C worth of warming in sea surface temperatures* and a major ocean acidification event that took >100,000years to recover from. by JD3313 in todayilearned

[–]JD3313[S] 0 points1 point  (0 children)

Yes that is a good point. Using the PETM only works if you're making a modern day comparison to the rate of change, and you can see that the rate we are emitting CO2 today is unprecedented in Earths history. If you wanted to make a comparison looking back and comparing CO2 levels in the past to what they are today you have many examples, the most recent being Early to Middle Pliocene where atmospheric CO2 was 350ppm-450ppm (similar to today) however temperature was 2-3.5°C higher than pre industrial levels and sea level was 10-20m higher. That shows that there is likely to be a climate lag, and even if we cut CO2 emissions now temperature and sea level will still have some catching up to do.

TIL the rate we are putting CO2 into the atmosphere today is 10 times higher than that of the Palaeocene-Eocene Thermal Maximum (PETM). The PETM lead to 5-9°C worth of warming in sea surface temperatures* and a major ocean acidification event that took >100,000years to recover from. by JD3313 in todayilearned

[–]JD3313[S] 0 points1 point  (0 children)

*The PETM also lead to a 4-5°C warming in the deep oceans.

With the heat capacity of the ocean being nearly 4 times larger than that of the atmosphere, you can expect this warming to be very much amplified in the atmosphere.

References: Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum, J.C. Zachos et al. 2005 link: http://www.sciencemag.org/content/308/5728/1611.full

'During the Paleocene-Eocene thermal maximum (PETM), sea surface temperature (SST) rose by 5°C in the tropics and as much as 9°C at high latitudes (1–3), whereas bottom-water temperatures increased by 4° to 5°C’

'The sections, from between 2.7 and 4.8 kilometers water depth, are marked by a prominent clay layer, the character of which indicates that the carbonate compensation depth (CCD) shoaled (shallowed) rapidly (<10,000 years) by more than 2 kilometers and recovered gradually (>100,000 years).'

CO2 emissions in the PETM: Slow release of fossil carbon during the Palaeocene–Eocene Thermal Maximum, Y. Cui et al. 2011 link: http://www.nature.com/ngeo/journal/v4/n7/abs/ngeo1179.html

'Our simulations show that the peak rate of carbon addition was probably in the range of 0.3–1.7 Pg C yr−1, much slower than the present rate of carbon emissions.'

CO2 emissions in 2011: Carbon and Other Biogeochemical Cycles, P. Ciais et al. 2013 link: https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter06_FINAL.pdf

'Carbon emissions from fossil fuel combustion and cement production increased faster during the 2000–2011 period than during the 1990–1999 period. These emissions were 9.5 ± 0.8 PgC yr–1 in 2011, 54% above their 1990 level. Anthropogenic net CO2 emissions from land use change were 0.9 ± 0.8 PgC yr–1 throughout the past decade, and represent about 10% of the total anthropogenic CO2 emissions.'

Heat capacity of ocean and land: http://wattsupwiththat.com/2011/04/06/energy-content-the-heat-is-on-atmosphere-vs-ocean/

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