What happens at 1.5℃ of warming?

The Earth hasn’t been that hot in over 100 thousand years [1]. At that time humans had no farming, and the animals and plants inhabiting Earth were quite different [2,3]. But what would +1.5°C mean in modern times?

So far, Earth has warmed by about 1°C above pre-Industrial levels [8], and this is already causing humans to die [10] and species to go extinct [9]. If Earth warms another 0.5°C, we expect things to get much worse: more extreme heatwaves, droughts, floods, and forest fires [11,12]; more spread of pests and disease [13,14]; more loss of land to rising sea levels [11]; and maybe food shortages [16].

Some wildlife is particularly vulnerable to warming, and less able to adapt than humans: it’s predicted that with +1.5°C, only 10% of coral reefs may survive [5]. Losing them would be a tragedy, since they provide food or shelter for over 25% of fish species in the ocean [17], and benefit humans through fishing, tourism, and flood protection [18].

Remember: +1.5°C refers to the global average increase in temperature, but warming will be different across regions [4]. With the same change in global temperature, some areas are predicted to be 4.5°C warmer [4]!

It is almost certain that we will reach 1.5°C of warming [6]. If we don’t massively change the way we live, this may happen as early as 2040 [6]. In theory, it is possible to stay below 1.5°C if we stopped emitting CO2 today, or if we quickly invent clever technology that cools the planet, but unfortunately, neither of these are likely to happen soon enough [6,7].

The effects of 1.5°C sound horrible already, but scientists think that the effects of 2°C would be much worse [4]. Yet, even these seem almost cute compared to 4° and even higher temperatures – see our next posts!

References

[1] https://www.pnas.org/content/pnas/115/52/13288.full.pdf

[2] https://www.ancient.eu/timeline/Agriculture/

[3] https://www.cambridge.org/core/journals/netherlands-journal-of-geosciences/article/eemian-mammal-fauna-of-central-europe/4FBC07DE56147B70F9ADFED99D34EF94

[4] https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter3_Low_Res.pdf

[5] https://www.ipcc.ch/2018/10/08/summary-for-policymakers-of-ipcc-special-report-on-global-warming-of-1-5c-approved-by-governments/

[6] https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter1_Low_Res.pdf

[7] https://pubs.rsc.org/en/content/articlehtml/2018/ee/c7ee02342a#tab1

[8] https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_SPM_version_report_LR.pdf

[9] http://www.publish.csiro.au/WR/WR16157

[10] https://ehp.niehs.nih.gov/doi/full/10.1289/EHP1509

[11] https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter1_Low_Res.pdf

[12] https://www.sciencedirect.com/science/article/pii/S0048969700005246

[13] https://www.nature.com/articles/nclimate1990?report=reader

[14] https://www.sciencedirect.com/science/article/pii/S1473309909701045

[16] https://www.pnas.org/content/105/32/11081.short

[17] https://www.nature.com/articles/s41586-018-0041-2?dom=scribd&src=syn

[18] https://www.researchgate.net/profile/Marcus_Oehman/publication/236628219_Economic_valuation_of_an_integrated_terrestrial_and_marine_protected_area_Jamaica’s_Portland_Bight/links/0046352cfd6c99c2d5000000/Economic-valuation-of-an-integrated-terrestrial-and-marine-protected-area-Jamaicas-Portland-Bight.pdf#page=12

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