Why global warming causes more warming

Article by Isabel Key and Mina Frost.

If you do a piece of work and get positive feedback from your teacher or boss, then you might work even harder on the next piece of work. This could form a cycle whereby you do well, so you do better the next time, then you do even better the time after that.

Positive feedback loops also exist in nature, but in the case of climate change they are not such a good thing; they accelerate global warming [1].

How does this work?

1) Humans produce greenhouse gas emissions, which warm the atmosphere (see our post on the greenhouse effect) [2]

2) Higher temperatures cause a change in the air, on the ground, or in the ocean, which makes temperatures increase even more [1,3]

Point 2 constantly reinforces itself, leading to a “snowballing” effect [3]. Climate feedback loops involve, for example: melting ice, melting permafrost, and water vapor [4] – we cover each of these in detail in other posts.

Together, climate feedback loops cause the global average temperature to increase much more than if human greenhouse gas emissions acted alone, without causing feedback loops [5]. It’s estimated that doubling the amount of carbon dioxide in the atmosphere would directly cause warming of 1.2°C; but due to feedback loops, the actual temperature change (after a time delay) would be between 2°C and 4.5°C [5]!

How feedback loops will respond to future warming is difficult to predict, and this is one of the main reasons we are so uncertain about how the climate will change in the future [6,4,7,8,9].

References

[1] https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_TS_FINAL.pdf See: TS.3.7 Climate Feedbacks

[2] https://www.ipcc.ch/site/assets/uploads/2018/02/AR5_SYR_FINAL_SPM.pdf Climate Change 2014 Synthesis Report Summary for Policymakers, IPCC 2014. Within report see: SPM 1.2

[3] https://www.soas.ac.uk/cedep-demos/000_P500_ESM_K3736-Demo/unit1/page_14.htm See: Feedback loops and equilibrium

[4] https://www.ipcc.ch/site/assets/uploads/2018/03/TAR-07.pdf See: Atmosphere processes and feedbacks, and Cryosphere processes and feedbacks; Executive Summary, especially paragraph 4

[5] https://www.pnas.org/content/110/45/18087.short See: paragraph 1 of main text

[6] https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_TS_FINAL.pdf See: TS.6.2 Key Uncertainties in Drivers of Climate Change

[7] https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL079429 See: Abstract

[8] https://www.nature.com/articles/s41558-018-0197-7 See: Abstract

[9] https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL078493 See: Plain Language Summary

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