Arctic News: Extreme Weather

Extreme Weather

Extreme weather events are occurring with greater frequency and intensity. We are also seeing more wild weather swings, in which heatwaves can be followed up by cold snaps, and droughts can be followed up by flooding, and visa versa.

How does global warming cause such wild weather swings? A number of mechanisms are discussed here, including more water vapor in the atmosphere and changes in wind patterns, such as Jet Stream changes and stronger winter storms.

Water Vapor

Rising temperatures will result in more water vapor in the atmosphere, further amplifying warming, since water vapor is a potent greenhouse gas.

For every 1°C warming, there will be 7% more water vapor in the atmosphere, so there will be 10.5 % more water vapor at 1.5° C warming.

As the IPCC says: "Water vapour feedback acting alone approximately doubles the warming from what it would be for fixed water vapour.

Furthermore, water vapour feedback acts to amplify other feedbacks in models, such as cloud feedback and ice albedo feedback.

If cloud feedback is strongly positive, the water vapour feedback can lead to 3.5 times as much warming as would be the case if water vapour concentration were held fixed", according to the IPCC.

More moisture gets into the air as evaporation from oceans, vegetation and soils gets stronger.

Stronger evaporation means that soils dry out faster - even after stronger rainstorms, soils will quickly dry out, resulting in soils that are overall more dry than they used to be. Soils that are dry are also more vulnerable to fire.

Changes in Wind Patterns

As the Arctic warms up faster than the rest of the world, the temperature difference between the North Pole and the Equator narrows, making the jet stream wavier, thus enabling cold air from the Arctic to descend further south, and hot air to move further north and enter the Arctic. The images on the right illustrate what can happen.

On February 4, 2018, it was as cold as -10°C or 13.9°F in Africa, while at the same time it was as warm as 5.8°C or 42.4°F near Svalbard.

The next image shows instantaneous wind power density at 250 hPa (jet stream) on February 4, 2018.

A warmer sea surface can cause winds over oceans to grow dramatically stronger. Furthermore, as oceans get warmer, the temperature difference between land and oceans increases in Winter.

[ NOAA Climate.gov cartoon by Emily Greenhalgh ]

This larger temperature difference in turn results in stronger winds that can carry more warm, moist air inland, e.g. into the U.S., as illustrated by the cartoon on the right.

Stronger winds from a warmer Atlantic Ocean can also push larger amounts of warmer and more moist air into the Arctic, while they can also speed up sea currents that cause larger amounts of warmer and more salty water to flow into the Arctic Ocean.

On January 23, 2019, sea surface temperatures at a spot near Svalbard were as high as 18.3°C or 64.9°F.

On December 8, 2018, sea surface temperatures near Svalbard were as much as 18.2°C or 32.7°F warmer than 1981-2011.

An influx of warm, salty water into the Arctic Ocean can dramatically speed up decline of Arctic sea ice and of terrestrial and subsea permafrost, resulting in more albedo losses and releases of greenhouse gases such as carbon dioxide, methane and nitrous oxide.

This illustrates how more extreme weather events go hand in hand with a number of interrelated feedbacks.

In the video below, Jennifer Francis explains the link between the jet stream and extreme weather events. For a transcript, see this page.

Arctic News

Extreme Weather

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