Thread by @CarbonBrief

Several #Arctic locations recorded land surface temperatures hitting 45C on 19 June, according to initial data from the @esa satellite Sentinel-3.

Here is what you need to know... (THREAD 1/7)

https://twitter.com/defis_eu/status/1275337831704035328

Also widely reported is a potential new Arctic temperature record of 38C in Verkhoyansk – a town in #Siberia, Russia – on 20 June

See @CarbonBrief’s Daily Briefing: carbonbrief.org/daily-brief/uk…

So why is 38C potentially a new record, but not 45C?

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The 45C reading is land surface temp – how hot the surface is to the touch – which is commonly measured by satellites.

The 38C reading is surface air temp – how warm the air is just above the ground. This is what is you usually see in weather forecasts and climate data.

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Typically, on a sunny day, the land surface temperature will be warmer than the air above it (see this paper: journals.ametsoc.org/jamc/article/5…)

But there’s no fixed relationship between the two as this varies with weather conditions

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Siberia’s heatwave is primarily the result of a “blocking” weather pattern. This is when a weather system – usually a high-pressure one – gets stuck in one place for days or even weeks.

Read more in @CarbonBrief’s Q&A: carbonbrief.org/jet-stream-is-…

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The block means any oncoming (cooler, wetter) weather is deflected away or also stays put.

Summer blocking events were the root cause of other major heatwaves, e.g. Europe in 2003 & Russia in 2010.

As this @BerkeleyEarth map shows, Siberia has seen a very warm 2020 so far

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Siberia is covered by vast stretches of #permafrost – frozen ground storing billions of tonnes of carbon.

High temperatures cause permafrost to thaw and potentially emit its long-held carbon. For more, see this @CarbonBrief guest post by @schaedelc

carbonbrief.org/guest-post-the…

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