The Arctic warms 2x faster than the global average. Why care?

Article by Isabel Key and Mina Frost.

The air temperature increase in the Arctic over the last 20 years was more than twice the global average increase in temperature [20]. This is causing ice to melt: the area of Arctic sea ice has decreased by around 13% per decade since 1980 [17]. One reason this is a big problem is that when ice melts it accelerates climate change [2,4,6,8].

Different surfaces reflect different amounts of light [3]. When sunlight hits ice, more of it is reflected back into space than when light hits other, darker surfaces [4,5,6,7].

When ice or snow melts on land, it often exposes a darker surface underneath such as soil or dark green trees [2,4,8]. Similarly, when ice floating on water melts, it exposes the dark ocean [6]. In both cases, melting ice results in the surface of the Earth becoming less reflective [2] – the ocean reflects about 7% of light that hits it, compared to 85% for ice [19]!

More sunlight is absorbed and released again as infrared radiation if the Earth’s surface is darker in colour [2,9]. The infrared radiation is then absorbed and re-emitted by greenhouse gas molecules in the air, which warms the atmosphere [10].

This forms a “positive feedback loop” [2,4,12,18,21]:

1) Humans release greenhouse gases, like CO2, which warm the atmosphere [11] 2) Ice melts due to higher temperatures [2] 3) Darker surfaces (e.g. ocean or forest) are exposed to sunlight [2] 4) Less light is reflected back into space [2]; more is absorbed by the surface of the Earth and re-emitted as infrared radiation [9] 5) The atmosphere heats up, bringing us back to step 2 [2]!

In some places, the Earth’s surface is also becoming less reflective due to some species of plant growing further north [14,15]. As the climate warms, trees and shrubs are able to survive closer to the North Pole [14,15]. Some snow can sit on top of plants, but overall the planet’s surface is becoming darker and less reflective, therefore contributing to warming [16].

References

[1]https://www.tandfonline.com/doi/full/10.1657/1523-0430(07-105)%5BHAMILTON%5D2.0.CO;2See: Opinions on Polar Issues

[2]https://climate.nasa.gov/resources/education/pbs_modules/lesson2Engage/See: Paragraph starting: “Albedo is a measure of…”

[3]https://www.bbc.co.uk/bitesize/guides/zq7thyc/revision/6See: Coloured light

[4]https://www.nature.com/articles/359716a0

[5]https://iopscience.iop.org/article/10.1088/1748-9326/aacf72/metaSee: Abstract

[6]https://www.britannica.com/science/global-warming/Feedback-mechanisms-and-climate-sensitivity#ref979387See: ice albedo feedback

[7]https://www.esa.int/SPECIALS/Eduspace_Global_EN/SEMPJ7TWLUG_0.htmlSee: reflectance curves for ice, vegetation, and water

[8]https://www.ipcc.ch/site/assets/uploads/2019/08/2c.-Chapter-2_FINAL.pdfSee: Executive Summary, “Regional climate change can be dampened or enhanced…”

[9]https://science.nasa.gov/ems/07_infraredwavesSee: monitoring the Earth

[10]https://www.acs.org/content/acs/en/climatescience/greenhousegases/properties.html

[11]https://www.acs.org/content/acs/en/climatescience/greenhousegases.html

[12]https://www.nature.com/articles/ngeo1062See: Abstract

[13]https://www.ipcc.ch/site/assets/uploads/2018/03/TAR-07.pdf

[14]https://epic.awi.de/id/eprint/41619/

[15]https://www.nature.com/articles/nclimate1558

[16]https://www.biogeosciences.net/14/4209/2017/bg-14-4209-2017.pdf

[17] https://report.ipcc.ch/srocc/pdf/SROCC_SPM_Approved.pdf See: A1.4

[18] https://www.ipcc.ch/site/assets/uploads/sites/3/2019/11/SROCC_FinalDraft_Chapter3.pdf See : 3.2.1.1.1, Extent and concentration, Paragraph 2

[19] http://enduringice.com/sea-ice-albedo-feedback/ See: Arctic Monitoring and Assessment Programme diagram

[20] https://www.ipcc.ch/site/assets/uploads/sites/3/2019/11/SROCC_FinalDraft_Chapter3.pdf See: Executive Summary

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

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