Jens Terhaar

It's scary how fast the earth is warming.

For a long time, the 🌊 ocean surface was warming at a slower 🐌 rate but the warming rate appears to have caught up 🐇.

➡️ In our study about the jump in SSTs, we also estimated a 0.27°C per decade warming of global SSTs (www.nature.com/articles/s41...)

Is a monster web of ocean currents headed for collapse? The race is on to find out Research ships rarely brave the Greenland Sea in winter. Early this year, scientists ventured into the ice-covered waters to capture crucial data about the planet’s future.

Informative and interesting news feature in @nature.com about the AMOC & large existing uncertainties about its past & future by @timkalvelage.bsky.social who accompanied oceanographer Kjetil Våge from @bjerknes.uib.no on the Norwegian ice-breaker RV Kronprins Haakon.

www.nature.com/articles/d41...

However, this does not mean that it is unexpected fast on the long term. It is an expected acceleration with added variability in my opinion. And every gram of reduced emissions s will reduce the warming rate

... for a long time. Once the sea ice disappears, warming will even more accelerate. In brief, I believe we come out of one or two decades with slower warming due to decadal variability and turn to a phase of faster warming now, we basically catch up to the long term trend as sea ice melts

... so much variability in the system. In the end, it is not surprising that warming is accelerating because emissions have continously risen. It was more surprising that warming was linear for such a long time. My take on that is that relatively robust sea ice has halted the acceleration...

I'd not take it out, the years 2023/24 were also exceptional because they years before were unusual cold compared to the long-term trend. So, it does not make much sense to remove it, I believe. However, statistical analyses 9f significance are important to be able to determine trends with...

It can also not be excluded at the moment that there is no unexpected accelerated warming in addition to the expected and observed acceleration of warming. But at the moment SSTs are consistent with climate models and can well be within expected accelerated warming based on emission increases

We adress the question by showing that SSTs as 2023/24 exist also in climate models, meaning that 2023/24 is not necessarily a sign of unexpected warming but can also be variability. @tguinaldo.bsky.social show that the Atlantic SSTs can also be explained by internal variability.

Increased future ocean heat uptake constrained by Antarctic sea ice extent Abstract. The ocean takes up over 90% of the excess heat stored in the Earth system as a result of anthropogenic climate change, which has led to sea level rise and an intensification of marine extrem...

The question that remains is if there is an additional unexpected warming. There are different possibilities, such as the Antarctic sea ice feedback that likely means that warming was lower over the last two decades and that warming will increase much more soon and ECS is larger than expected 😢👇

Temperatures would still have accelerated more in the last decade than in any decade before. Simply because emissions habe never been that high. It expected to see an accelerated warming if emission increase as they did over the last decades, with or without the jump in 2023/24

Updated Climate Visuals

(1) Warming stripes for atmosphere and ocean
(2) Climate indicators (adding land humidity for 2024)
(3) UK climate indicators (adding some 2024 data)

ed-hawkins.github.io/climate-visu...

We explained what caused the unusual winds (persistence of NAO- conditions and blocking syste over the British Isles) and showed also that the key factor that boosted this event is the long-term stratification which is linked to anthropogenic activities.

Internal variability effect doped by climate change drove the 2023 marine heat extreme in the North Atlantic - Communications Earth & Environment The 2023 North Atlantic marine heatwave was driven by an extreme phase of internal atmospheric variability but would have been impossible without the doping effect of anthropogenic warming, according ...

If I can add something. Here we demonstrate that NATL warming was due to natural variability. The event was excepted and in line with climate projections (return period around 10 years). The processes are well known and we can explain it.

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

And if SSTs do not return to pre-jump levels, this event is another indicator for a higher ECS/TCRE than previously estimated. There is really not much good news here.

It is really unfortunate that this is mis-used. The event has been extreme and it had extreme effects. And it would not have been possible without the strong underlying warming trend. So there is really not much good news here.

They are, however, not "expected" that often. Given that it is a 1-in-512 years event under current warming, the likelihood is higher that it had not occurred than that it occurred (assuming that we will reduce emissions and hence the warming trend in the next 100 years)

The title has different aspects, that is right. We came more from the modelers perspective and were also trying to rectify this statement: www.nature.com/articles/d41.... It was important to us that models can simulate such events. They are hence "expected"

That is unfortunate, everyone should know by now that warming scales with cumulative emissions. If emissions are higher, warming is faster, emissions have increased, hence warming has accelerated. In the scientific community, there is no disagreement, I believe or better I hope

I believe warming has accelerated, it is not a belief, it is measured. But has it accelerated more than expected based on emissions, I don't think so yet

I think it is a false security to rely on past warming as unknown feedbacks like this sea ice feedback will kick in with a high likelihood. At least that's what I believe

It is in brief a large decadal variability that kept warming low. Once we get out of this negative phase, temperatures will rise faster. This will not be an acceleration, just a back to normal. It will look like an acceleration though

Increased future ocean heat uptake constrained by Antarctic sea ice extent Abstract. The ocean takes up over 90% of the excess heat stored in the Earth system as a result of anthropogenic climate change, which has led to sea level rise and an intensification of marine extrem...

We argue exactly this in this preprint:

egusphere.copernicus.org/preprints/20...

We believe that the Antarctic sea ice has kept global warming relatively low. Once it melts, warming will be much faster. Thus, past warming dies not inform well about future warming or ECS

If SSTs don't come back soon, I think it is reason to panic even more about climate change as we already should do. Not because warming would have accelerated but because climate sensitivity is probably higher than expected.

It might be cloud-driven and it would be exciting to look if climate models show similar cloud patterns as observed during the global heatwaves.

Is that for the North Atlantic only as in your plot? The reason why I have doubts about the aerosol argument is that almost all global heatwaves were exceptionally warm im the North Atlantic and North Pacific even without aerosols.

I guess my pas exchanges with other people have made me somewhat sensitive towards not always well meant humorous comments 🥺 I see that this was not at all the case here and that it was a very balanced presentation. Thanks a lot for the clarification

Fully agree :)

Thanks for explaining. That helps a lot

Unfortunately, I could not attend this talk. Do you know how this was presented. I feel it very disrespectful towards our author team to present us basically as ignorant, stupid idiots. But maybe it was presented orally in a different way? 🤔

If you show the graph with the change in radiation, it would be better to also show the same lines from models to compare it accurately