Sebastian Sippel

Accelerated north–east shift of the global green wave trajectory | PNAS Viewed from space, a “green wave” seasonally traverses Earth’s surface, from the north in boreal summer to the south in austral summer. This wave r...

Very happy to finally share a paper that has been in my mind for a long time 🌍 🔗 www.pnas.org/doi/10.1073/...

Global greenness in September. Shown is a globe depicting average global terrestrial greenness in September, visualized as “height over ground” and averaged over the period 2000–2023. Greenness is derived from satellite remote-sensing observations provided by NASA’s Moderate Resolution Imaging Spectroradiometer and illustrates the large-scale spatial distribution of vegetation activity across the terrestrial biosphere. CREDIT: Ida Flik

The wave of green that sweeps Earth from the north in boreal summer to the south in austral summer is shifting due to climate change. Researchers found the centroid of the wave moving northward since 1982 and eastward since 2010. In PNAS: https://ow.ly/PjPU50YmYKz

Quantifying the time of emergence of the anthropogenic signal in the global land carbon sink Abstract. The global land carbon sink has increased since the pre-industrial period, driven by the increasing atmospheric CO2 concentration and physical processes influenced by climate change. However...

How long does it take for the anthropogenic effects on the land C sink to be detected, given the large year to year variability? And can we shorten the time of emergence in observations by removing the circulation-induced components?
Find more in Na Li’s study bg.copernicus.org/articles/23/...

Considerable yet contrasting regional imprint of circulation change on summer temperature trends across the Northern hemisphere mid-latitudes Abstract. Rising summer temperatures and more frequent heat extremes are well-documented outcomes of anthropogenic climate change. However, the extent to which atmospheric circulation changes contribu...

Summer temperatures have strongly been influenced by circulation changes in the northern mid-latitudes.

In our new study we evaluate and compare 4 statistical and ML methods that decompose trends into a "thermodynamical" and a "circulation induced" part.
wcd.copernicus.org/articles/7/8...

Emergence of strong trends in humid heat intensity and duration in recent decades over South Asia Emergence of strong trends in humid heat intensity and duration in recent decades over South Asia, Singh, Jitendra, Singh, Deepti, Sippel, Sebastian, Fischer, Erich

🥵 📜 New paper on the emergence of trends in humid heat intensity and duration in recent decades over South Asia led by Dr. Jitendra Singh with @sebastian-sippel.bsky.social @erichfischer.bsky.social
doi.org/10.1088/2752... via @ioppublishing.bsky.social

This week, we had a great retreat with our PhDs, Postdocs & PIs in Leipzig @idiv-research.bsky.social

Apart from sharing our progress, we hosted a session on extreme events with guest speakers @sebastian-sippel.bsky.social & @miguelmahecha.bsky.social
Thanks for the insightful talks & discussion!

Understanding past climate events and trends to constrain near-future climate risk The global mean surface temperature record —combining sea surface and near-surface air data— is central to understanding climate variability and change.

🚀 New season: AI for Good Webinar Series 𝗙𝗿𝗼𝗺 𝗠𝗼𝗹𝗲𝗰𝘂𝗹𝗲𝘀 𝘁𝗼 𝗠𝗼𝗱𝗲𝗹𝘀 - starting TODAY!

@sebastian-sippel.bsky.social (Leipzig University) discusses how past climate events inform future climate risks.

📅 Oct 1st
🕓 17:00-18:00 CEST

Sign-up: aiforgood.itu.int/event/unders...

Es ist eine grosse Ehre, den 2025 Deutschen Umweltpreis zu erhalten! Danke an alle meine jetzigen und ehemaligen Gruppenmitglieder und viele Kolleg:innen!
@lukasgudmundsson.bsky.social @yasserhaddad.bsky.social @yannquilcaille.bsky.social @michaelgwindisch.bsky.social @usyseth.bsky.social

Hosted by @meteoleipzig.bsky.social @unileipzig.bsky.social @tropos-de.bsky.social , ECO-N research training group funded by @dfg.de
Great lectures by @sebastian-sippel.bsky.social @frediotto.bsky.social @mdebrito.bsky.social @zscheischlerjak.bsky.social and more!

The current Advanced Training Module on "Climate Attribution", joinly by our interdisciplinary research training group "Economics of Connected Natural Commons" and the Leipzig Graduate school on Clouds, aerosols and radiation sparked large interest: 65 PhD researchers from 7 countries!

NEW – Guest post: How climate change is fuelling record-breaking extreme weather | @erichfischer.bsky.social‬

Read here: buff.ly/bnrSvQN

High warming rate fuels record-breaking weather

The longer our measurements, the fewer record-breaking events we should observe.

The opposite is the case - many more records and higher record margins

I summarise the key takeaways of our ‪@natrevearthenviron.nature.com article in a guest post.

Record-breaking extremes in a warming climate Nature Reviews Earth & Environment - Multiple record-breaking climate events have been observed, posing socioeconomic risks. This Review outlines observed and projected changes in...

Find the original @natrevearthenviron.nature.com article with important contributions from co-authors Margot Bador, Raphaël Huser, Lizzie Kendon, Alexander Robinson, and @sebastian-sippel.bsky.social
rdcu.be/eqPrN

🚨New Review!

'Record-breaking extremes in a warming climate'

By ‪@erichfischer.bsky.social, @sebastian-sippel.bsky.social et al.

www.nature.com/articles/s43...

Schematic illustrations of the onset mechanisms of compound heat flash droughts and non-heat flash droughts

⚒️ Article: Flash droughts that are accompanied by extreme heat drive more severe and prolonged impacts on global ecosystems

@erichfischer.bsky.social @ethz.ch @louiseslater.bsky.social @sebastian-sippel.bsky.social @retoknutti.bsky.social

www.nature.com/articles/s41...

Constraining the time of emergence of anthropogenic signal in the global land carbon sink Abstract. The global land carbon sink has increased since the preindustrial period, driven by increasing atmospheric CO2 concentration and climate change. However, detecting these anthropogenic signal...

How long does it take until we detect forced signals in global and regional land carbon fluxes?

And can we use dynamical adjustment to reduce the noise and shorten the detection time?

Check out LiNa's paper 👇
egusphere.copernicus.org/preprints/20...

Co-advised by @sebastian-sippel.bsky.social

5/4 p.s: The new paper by Ishii and colleagues (t.co/YeCrlimA3N) also highlights the sudden changes in NMAT (HadNMAT2 vs. CRUTEM5) around the mid-1910s in their Figure 3.

4/4 The year 1914 is characterised by a strong El-Nino (the uptick is seen consistently in land, SST and NMAT temperatures), the start of WWI and a sudden change in data sources (figure 2 below). Whether any of those events is responsible for the NMAT changes during this time, remains to be seen.

3/4 So it is crucial to better understand the NMAT puzzle piece, as the evidence that comes from ClassNMAT from the perspective of the GMST reconstructions from land vs. ocean is rather split for the 1900-1930 period. It may tell us something important about the ~1900s (1900-1913) vs. 1914 onwards.

2/4 The result is puzzling (figure 1 below, ClassNMAT seen in panel a and b): GMST based on NMATs is indeed *very* cold in the 1900s, following the SST-based GMST time series up until 1913. Yet, from 1914 onwards, the NMAT-based reconstruction is close(r) to the LSAT-based reconstruction...

Revised historical record sharpens perspective on global warming Undercorrection of ocean surface temperatures revealed.

1/4 Thanks for sharing your reflections! fascinating to read the more personal take behind the nice News&Views piece (www.nature.com/articles/d41...).
Just one after-thought on night marine air temperatures (NMAT). NMATs are a crucial puzzle piece, and we ran a GMST reconstruction for ClassNMAT:

very interesting project! I'm looking forward to learn about the results...

Early-twentieth-century cold bias in ocean surface temperature observations - Nature Independent statistical reconstructions of the global mean surface temperature from either ocean or land data show that existing estimates of early-twentieth-century ocean surface temperatures are too...

New paper by Sebastian Sippel and colleagues provides evidence that the SST component of most current global temperature datasets is too cold during (roughly) 1900-1930.
doi.org/10.1038/s415...

Early-twentieth-century cold bias in ocean surface temperature observations - Nature Independent statistical reconstructions of the global mean surface temperature from either ocean or land data show that existing estimates of early-twentieth-century ocean surface temperatures are too...

A new paper led by Sebastian Sippel just appeared in Nature arguing that ocean temperature measurements in the early 20th century have a cold bias.

It's a fun story illustrating the process of scientific discovery, so let me talk about it a bit. 🧵

www.nature.com/articles/s41...

Redrawing the global warming stripes.

In a new paper led by Sebastian Sippel published in Nature today, we show that the early 20th century global ocean surface temperatures and thereby global mean surface temperature were warmer than previously thought.

Thread... (1/13)

Early-twentieth-century cold bias in ocean surface temperature observations - Nature Independent statistical reconstructions of the global mean surface temperature from either ocean or land data show that existing estimates of early-twentieth-century ocean surface temperatures are too...

Breaking News!

Seminal paper by our own Sebastian Sippel & colleagues published in Nature @natureportfolio.bsky.social today! They provide evidence that the Sea Surface Temperatures in most current global temperature datasets are considerably too cold (1900-1930):

www.nature.com/articles/s41...

interesting discussion! i've been thinking along similar lines - sea level pressure, precipitation or even sea level height measurements at the time could give very interesting constraints...