Mika Rantanen Profile picture
Aug 11, 2022 13 tweets 7 min read Read on X
🚨New paper alert 🚨

I'm excited to announce that our open-access paper "The Arctic has warmed nearly four times faster than the globe since 1979" is now out in @CommsEarth: nature.com/articles/s4324…

#ArcticAmplification #Arctic

Thread of the main results:

1/13
We report that the Arctic has warmed four times faster than the globe in the last 43 years.

The four-fold Arctic amplification (AA) ratio is higher than what is generally reported in literature and media.

2/13
One reason for the higher ratio is that we defined the Arctic properly (with the Arctic Circle, 66.5°N), and calculated the trends since 1979 when satellite data became available.

With these parameters, the observed AA ratio is 3.7-4.1, depending slightly on the dataset.

3/13
More importantly, the unabated warming in the Arctic over the last two decades has raised the moving 43-year Arctic amplification ratio from two to four. Earlier estimates of 2/3x warming may be thus outdated.

4/13
Regionally, the warming has been even stronger. Areas in the Barents Sea near Novaya Zemlya have warmed up to seven times the global average, as recently reported in @SciReports by @Ketil_Isaksen et al: nature.com/articles/s4159…

5/13
Or course, the observed AA ratio depends on the area definition of the Arctic and the time window used for the linear trends.

The higher the Arctic latitude threshold, the stronger AA, as a larger proportion of the area is ocean (where AA is the strongest).

6/13
Furthermore, we found evidence that climate models, when considered as a group, cannot reproduce the observed four-fold AA ratio over 1979-2021.

We used ensembles from CMIP5, CMIP6, MPI-GE and CanESM5 models.

Similar result was recently reported in GRL: agupubs.onlinelibrary.wiley.com/doi/10.1029/20…
Those models that show plausible Arctic warming trend typically have too much global warming. In contrast, those models that simulate global warming close to that observed, generally have too weak Arctic warming.

8/13
Even when allowing a longer time window for the models than for observations (because internal variability is not in phase in models and observations), the difference between simulated and observed 43-year AA ratios was found to be statistically significant (except for CanESM5).
Arctic amplification has seasonal cycle, with lower AA in summer and higher AA in late autumn/winter.

CMIP6 models systematically underestimate the observed AA, especially during the melting season.

A particularly interesting finding was the anomalously high AA in April.

10/13
It's important to stress that the model-observations discrepancy is smaller when using a longer time window for the warming trends (i.e. 1950-2021).

The plots below show the AA ratio as a function of the starting year of the linear trends.

11/13
This indicates that internal climate variability may have contributed considerably to the observed AA ratio over 1979-2021. It is also possible that climate models have biases which makes them systematically underestimate the Arctic amplification. More research is needed.

12/13
End. Huge thanks to my co-authors Alexey Karpechko, @anttilip, @kalle_nordling, @OttoHyvarinenIL, Kimmo Ruosteenoja, Timo Vihma and @AriJLaaksonen.

This was a group effort with diverse contribution from various units of @ilmatiede. So glad that the paper finally came out!

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Mika Rantanen

Mika Rantanen Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @mikarantane

Feb 1
Happy to announce a new paper from me and @AriJLaaksonen:

The jump in global temperatures in September 2023 is extremely unlikely due to internal climate variability alone

published today in @Nature_NPJ Climate and Atmospheric Science.



Thread (1/8) nature.com/articles/s4161…
Image
As you probably remember, September 2023 was a record-warm month globally with an unprecedented margin of 0.5°C.

In this Brief Communication, we show that such a large margin is a very rare event in the climate models, occurring in about once in a hundred simulations.

(2/8) Image
In the CMIP6 models, for example, only three (!) of all 5166 model-simulated margins from 244 simulations exceed the observed 0.5°C margin in 1970-2050.

(3/8) Image
Read 8 tweets
Jan 3
#Pakkanen puhuttaa. Miten meneillään oleva pakkasjakso sopii yhteen #ilmasto'n lämpenemisen kanssa?

❄️🌨️🥶

Muutama ajatus pitkähkössä ketjussa 👇🧵: (1/13)
Ensinnäkin, globaalia ilmaston tilaa ei saa selville vain takapihalle tuijottamalla tai paikallisia säätilastoja tutkimalla.

Suomi on ollut pohjoisen pallonpuoliskon kylmyyspiste viimeisen kuukausien aikana. (2/13) Image
Siinä missä loka-joulukuu oli Suomessa 3. kylmin tällä vuosisadalla, globaalisti ne olivat ennätyslämpimiä.

#Ilmastonmuutos etenee Suomen pakkasista huolimatta. (3/13) Image
Read 13 tweets
Apr 25, 2023
Summer is approaching in northern extratropics and with summer comes the heatwaves.

Although it's still April, a major summer-like heatwave will hit Spain this week. Temperatures are forecast to rise close to 40°C which would be unprecedented for April. #AprilHeatwave Image
The dynamic development of the heatwave is worth highlighting.

Blocking high acts like a stone in the river by causing a split of the jet stream and the occurrence of a double jet situation. Image
As a side note, the synoptic situation reminds me of the recent paper by @syn_efou et al. who found that the increasing trends of western European heatwaves are to linked more persistent double jet situations:

nature.com/articles/s4146…
Read 7 tweets
Dec 14, 2022
Runsas lumitilanne ja viileä alkutalvi Etelä-Suomessa puhuttaa.



Onko #ilmastonmuutos-ennusteet pielessä vai mistä tämä johtuu?

Ketju aiheesta 🧵 👇
Ensinnäkin pitää muistaa, että talvi-ilmasto on Suomessa luonnostaan hyvin vaihteleva, eikä vaihtelun odoteta loppuvan tulevaisuudessa.

Kylmät talvet ovat tulevaisuudessakin mahdollisia, vaikkakin niiden todennäköisyys hiljalleen pienenee ilmaston lämmetessä.
Myös lumensyvyydessa on luonnostaan suurta vuosien välistä vaihtelua. Tästä esimerkinä neljä runsaslumista talvea 2010-2013, joista voit lukea lisää täältä: rmets.onlinelibrary.wiley.com/doi/10.1002/we…

Pitkän ajan trendi lumensyvyyssummassa on kuitenkin laskeva, varsinkin Etelä-Suomessa.
Read 9 tweets
Jun 24, 2022
Miksi viimeaikaisissa helleaalloissa on ollut niin kuuma? Mitkä ilmakehän tekijät selittävät korkeita lämpötiloja? #helle #helteet

KETJU 🔗aiheesta (1/7):
Ensimmäinen, melko selvä syy on lämpimien ilmamassojen virtaus eteläisimmiltä leveysasteilta.

Ranskaan virtasi kuumaa, Saharan ilmamassaa Afrikasta, ja meidän juhannushelteet selittyvät osaltaan lämpimällä ilmavirtauksella Etelä-Euroopasta (kuvan nuoli).

(2/7)
Toinen syy liittyy korkeapaineiden dynamiikkaan. Olet varmaan huomannut, että pumpatessa ilmaa renkaaseen pumppu kuumenee. Samaa tapahtuu korkeapaineissa!

Laskeutuvan ilmapaketin paine kasvaa, ja fysiikan lakien mukaan sen lämpötila nousee.

(3/7)
Read 7 tweets
Jun 13, 2022
A major heatwave will hit this week to western Europe.
Temperatures over 40°C are expected in France and widely in Spain.

And this all will happen after a record-warm May in France and the 2nd warmest May in Spain.

Some thoughts in a thread 👇
The heatwave forms when an upper-level ridge strengthens in the downstream of the Azorean cut-off low.

The ridge involves hot airmass from Africa, and perhaps more importantly, descending air parcels adiabatically warming when reaching surface.
The evolution resembles 2019 western European heatwave, but this time the downstream ridge responsible for the heatwave does not grow as strong in amplitude, and also the wave breaking looks more cyclonic (or less anticyclonic) than in 2019.
Read 6 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Don't want to be a Premium member but still want to support us?

Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!

Ethereum

0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy

Bitcoin

3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us!

:(