Mika Rantanen

Excited to share that our new paper “Summer 2024 in northern Fennoscandia was very likely the warmest in 2000 years” has been published in npj Climate and Atmospheric Science! See the open-access paper from doi.org/10.1038/s416... Short thread 👇

New publication! In our review published in @globalchangebio.bsky.social : we discuss what is climate change experienced by life on Earth 💧🌡️❄️ Led by @linegreis.bsky.social @evagril.bsky.social @ilyamaclean.bsky.social @jlembrechts.bsky.social and @kvanmeerbeek.bsky.social 📜 doi.org/10.1111/gcb....

Extraordinary warm autumn continues in southern Finland. The mean temperature in Helsinki so far this October is 10.1 °C, and it is not expected to decrease much in the coming days as the warm airflow will keep temperatures close to 10 °C both day and night.

While there is increasingly strong evidence that global warming is accelerating, we need to be careful about how we detect it. Unfortunately a newly published paper on the topic makes a number of mistakes in it approach, as I discuss over at The Climate Brink:

New publication! Our study led by @mikarantane.bsky.social in Theoretical and Applied Climatology shows the spatial heterogeneity in growing season dynamics across northern environments 🍃🌡️🥵

Le service météorologique islandais confirme un nouveau record de plus basse pression mesurée en octobre en Islande avec 934,6 hPa à Fagurhólsmýri hier 14 octobre 2026 (ancien 938,4 hPa à Stórhöfði le 19 octobre 1963). Hier une rafale de 205 km/h a été mesurée à Hvammur. www.vedur.is/um-vi/fretti...

New study suggests that AMOC collapse it not necessarily a tipping point but AMOC can recover if the planet cools. www.science.org/doi/10.1126/...

Syyskuu oli jo toinen peräkkäinen kuukausi, jolloin globaali lämpötila ylitti 1,5 asteen rajan. Myös 365 päivän liukuva keskiarvo on jälleen takaisin 1,5 asteeessa. Lue lisää tiedotteesta: www.ilmatieteenlaitos.fi/tiedote/4efm...

Still notably marked positive pressure signal over Greenland for late winter (February), and southward shifted Atlantic storm track in the latest C3S seasonal forecasts. It's a super consistent signal given it's multi-model mean, across all modeling systems, meaning hundreds of ensemble members.

Today is, climatologically, the fastest-cooling time of the year in Helsinki: the average seasonal temperature curve declines most rapidly around 9 October. For the nerds: this shows the time derivative of the 31-day-smoothed mean daily temperature. Winter is coming!❄️

It's all but certain that the first hurricane of the 2026 Atlantic hurricane season will go in the books on October 8. During the satellite era (I'm using 1966), that is BY FAR the latest... by 27 days! It's an incredible 63 days after the median date.

Isaias on Atlantin ensimmäinen hurrikaani tänä syksynä - myöhäisin ensimmäinen hurrikaani koko satelliittiaikakaudella. Isoin syy El Niño, joka lisää tuulisuutta Atlantilla ja siten vaikeuttaa hurrikaanien kehittymistä.

Number of windstorms, or days with stormy winds (21 m/s), has been unusually low in Finland this year. Jan-Sep period gave only 5 storm days, which is the 2nd lowest number since 2006 when the reporting period starts. More in @suomenluonto.bsky.social (in Finnish): suomenluonto.fi/myrskyjen-ma...

Ylen jutussa yle.fi/a/74-20249365 oli @ilmatieteenlaitos.fi eli meidän tekemä helle-ennuste vuodelle 2040. Esimerkkinä oli 17.7.2018 hellepäivä, joka simuloitiin Climate DT storyline-ajolla +2 asteen ilmastossa. Simulaation perusteella sama säätilanne olisi vuonna 2040 noin 1,8 °C lämpimämpi.

Suomen Ilmastopaneeli @ilmastopaneeli.fi julkaisi tänään raportin "Ilmastonmuutoksen tilannekuva 2026 – Miten ilmastonmuutos etenee ja vaikuttaa Suomessa ja globaalisti" ilmastopaneeli.fi/hae-julkaisu... Suomi on lämmennyt jo noin 2,5 astetta esiteollisesta ajasta.

Vuonna 2024 Jari-myrskyn yhteydessä havaittiin Perämerellä poikkeuksellisen alhaisia vedenkorkeuksia. Tutkijat selvittivät, mistä ennätyksellisen alhaiset vedenkorkeudet johtuivat. Lue lisää uutisesta👇 www.ilmatieteenlaitos.fi/uutinen/6ZEj...

The 10th Copernicus Ocean State Report (OSR10) was published today: marine.copernicus.eu/news/publica... In the report, we have a paper on record-low sea levels in the Bothnian Bay in Nov 2024, caused by an extreme windstorm event (Storm Jari). Open-access paper: sp.copernicus.org/articles/7-o...

Do you remember the drought affecting Finland that received a lot of media attention? In early May, cumulative precipitation was record-low in Finland. Turns out that the summer and September were quite wet, and cumulative precipitation in Finland is now actually above average!

New paper by @daanvandenbroek.com and me just published in @rmets.org Weather: "The 2026 cold wave brought northern Fennoscandia its coldest 2-week period since 1987" rmets.onlinelibrary.wiley.com/doi/10.1002/... Check out the brilliant thread by Daan below 👇

Radar image of Tuesday's mass crane migration. A 100 km long line of migrating cranes was clearly visible on weather radar. It is estimated that around 10,000 (?) cranes were involved in that formation. The highest count observed was 26,000 migrating cranes on that day in Kangasala (near Tampere).

Just accepted! Our study led by @mikarantane.bsky.social in Theoretical and Applied Climatology shows the spatial heterogeneity in growing season dynamics across northern environments 🍃🌡️🥵 While waiting for the final publication, you can check out our preprint version: doi.org/10.21203/rs....

Another new paper on the acceleration debate: "Space-time signatures of surface warming accelerations since 1970" www.nature.com/articles/s41...

🚨New publication How does internal climate variability affect the calculation of the ETCCDI temperature and precipitation extreme indices? In our paper, we introduce the Variability Atlas, a flexible toolset to address this question for users of all experience levels! doi.org/10.1088/1748...

Composites of winter (DJF) temperature anomalies of moderate-to-strong ENSO events (RONI threshold ±1.0 °C) in Europe. Note, these are detrended temperature anomalies. The pattern is cold for northeastern Europe but closer inspection reveals that two winters (1987 and 2010) push the average down.

El Niñon voimakkuus saavutti tiistaina kolmen asteen rajan, Ilmatieteen laitoksen tutkija Mika Rantanen sanoo. "El Niño voimakkaasti lämmenneessä ilmastossa on yhdistelmä, jota ei ole koskaan aikaisemmin koettu." www.is.fi/kotimaa/art-...

Kollega A-J Punkka on tässä oikeassa - harvoin syyskuussa tehdyssä kausiennusteessa on niin selkeä signaali talvikaudelle. Selvästikin malleissa on jokin driveri, (El Niño?), mikä työntää niitä samaan asentoon. Tuleva talvi on El Niñon kaukovaikutusten "stressitesti"? yle.fi/a/74-20246396

Classic El Niño signal is visible in the latest C3S seasonal forecasts for the upcoming winter. The multi-model mean MSLP anomaly is almost a carbon copy of El Niño composite for the Jan-Feb period. confluence.ecmwf.int/spaces/CKB/p...

Job alert: full professorship in meteorology in the University of Helsinki! New position in dynamic meteorology, synoptic-scale meteorology and numerical weather prediction. The vacancy has been opened due to the passing of Dr. Victoria Sinclair. Details: jobs.helsinki.fi/job/Helsinki...

Melko voimakas lintujen aamumuutto käynnissä selkeällä taivaalla. Lähinnä hyönteissyöjiä kuten kuten västäräkkejä ja rautiaisia poistuu Suomesta.

8 years ago, I tweeted side-by-side maps from NASA GISS showing global temperatures in 1976 and 2018 – both hot summers in the UK. It subsequently went viral and was printed in the Daily Mail! The 2026 version is stark. Two locally extreme summers separated by 50 years of global climate change.

Job alert: full professorship in meteorology in the University of Helsinki! New position in dynamic meteorology, synoptic-scale meteorology and numerical weather prediction. The vacancy has been opened due to the passing of Dr. Victoria Sinclair. Details: jobs.helsinki.fi/job/Helsinki...

Climate change increases deadly heat risk in Southern Europe. Across 34 countries, 2022-like heat mortality events were 26.5× more likely in Southern Europe than under pre-industrial conditions, ~10× the European average. Risk rises sharply with warming. www.nature.com/articles/s44...

The #Arctic (land & seas poleward north of 60ºN) finished up with the warmest summer on record in ERA5 data from @copernicusecmwf.bsky.social. The five warmest summers all since 2016. However, within 1100km (700 miles) of the North Pole (80° to 90°N) this was the coolest summer since 2014. #Climate

Summers are warming so fast in the UK that scientists can’t keep track. Abstract of a new study: “Summer 2025 was the warmest so far recorded for the UK” The paper was published today, and indeed, that "so far" was a useful addition. rmets.onlinelibrary.wiley.com/doi/10.1002/...

Summer 2026 is provisionally the UK’s warmest summer on record with the season’s mean temperature made around 130 times more likely due to human-induced climate change. Here, we delve into the numbers 🧵

Happy autumn! Summer 2026 in Finland was very close to the 1991–2020 averages, and even slightly above it. It may feel counterintuitive, but I'd argue it's part of the shifting baseline -syndrome. We just didn't have those week-long heatwaves this year, as opposed to western Europe.

Globally, the hottest August in observed history is just about to end. In Western Europe, the summer of 2026 (June, July, August) has been the warmest as well. Compared to this year, 1976 (the famous UK summer) and 2003 (the hottest EU summer so far) look like amateurs in terms of heat (1/2)

Exceptionally cold morning in eastern Lapland with minimum temperature down to -6.6 °C in Savukoski Tulppio. This is the coldest August temperature observed in Finland since 1986, and it ties the -6.6 °C reading from August 1989.

Children disproportionately affected by heat Our new Science Advances paper, led by @rosapietroiusti.bsky.social and @wimthiery.eu, shows that children today – and in the future – are disproportionately affected by heat stress. www.science.org/doi/10.1126/...