I'm not sure I understand your main point; I could summarize it to either one of the following:

"Which mechanisms that already exist in the earth/climate system could be utilized and amplified (and how), in order to mitigate the impact of the surface energy imbalance that is attributed to greenhouse gases? ",

or:

"Which mechanisms of energy dissipation and transportation would be naturally amplified in an earth/climate system, as a response to an increase in net surface energy? ".

In either case, your argumentation sways between simple concepts which can receive simple explanations, to more complex ones whose mechanisms are still subject to some degree of uncertainty. I think that the different levels of complexity would not all fit together very well in a single representation of the system.

For example, the main question you start with: "What does an extreme Earth's energy imbalance of 2.1 W/m2 or higher mean?", is a bit vague and general, so a straightforward answer could be that, if a closed thermodynamic system receives a surplus of energy, it's temperature is going to rise. A conclusion that doesn't help much.

This has been extensively studied in the past for the earth system, using simple energy balance models. By tweaking the values in the parameterization of the energy balance mechanisms, one can achieve an energy imbalance in the system, perform a sensitivity analysis and assess which parts of the system are affected, and which are contributing the most. This approach has been extensively applied, and can be found in the relevant literature.

For instance, implementing a zonally-averaged Budyko-Sellers energy balance model, can be seen in [Oerlemans and Dool, 1978] (https://doi.org/10.1175/1520-0469(1978)0352.0.CO;2), who examined the effects of the feedback between a long-term astronomical variation on the insolation value and variations in surface ice coverage (or changes in albedo). Even with a relatively simple climate model, we can see complex behaviors emerging, and multiple points of equilibrium.

An increased level of model complexity is continuously implemented ever since, leading to the currently used state-of-the-art climate numerical models. The contributions of individual mechanisms on the system are highly complex and non-linear, with some degree of uncertainty retained in most cases.

So, I would argue that direct and simple one-to-one relations like the ones you imply in your examples are difficult to find.

Thx for your kind answer Stamatios.

I will clarify my question: are there direct consequences of an EEI of 2.1 W/m2 in regard to an increase in emitted longwave radiation to space? And if so by which intensifying mechanisms/systems the Earth system would achieve this?

"So, I would argue that direct and simple one-to-one relations like the ones you imply in your examples are difficult to find." This is exactly what I wonder about.

Just one observation of the last two months:

We saw how warm and moist air masses are pumped high into the central Arctic over the North Atlantic sector, while cold air is pushed out over Eurasia and North America in December 2023 and January 2024. Maybe coincidence, maybe a direct consequence of such a high EEI as it happens to the extreme. Sure it happened in the past but the warm, moist air intrusions in DJ(F) 2023/24 seem to be a new record. But a study would have to clarify that. Here you can see the one just occurring now (attached also a picture) https://earth.nullschool.net/#current/wind/isobaric/850hPa/orthographic=-25.85,39.96,401

I think it a highly relevant research question, as the climate system now reached a new state with warming now at ~1.5°C while the EEI went also through the roof both likely mutually reinforcing extreme events of any kind. But maybe a jump of the EEI does not have any short-term consequences as the Earth system needs time to reconfigure around an EEI of such a magnitude. Or maybe the higher the EEI the faster the reconfiguration towards increasing amounts of emitted longwave radiation to space? Another important research question - are there non-linearities involved?

All the best

Jan

Thank you for the clarification Jan.

In that case I agree with you that the subject is both interesting and in need of further investigation. The calculation of the EEI is performed in a climatic sense over decade-long scales. So, in the approach you propose, I think that it is necessary to do a similar averaging and compare the anomaly of the intensity of all the metrics/mechanisms that you mention against anomalies in EEI.

Nevertheless, I would argue that the situation you examine in your test case, is a rearrangement of heat through advection within the system itself, and of course it is being examined on the scale of synoptic meteorology and not the climatic one. Even after all the statistics and averaging, you will still have to explain the mechanism of how an anomaly in, say, 850hPa southerly winds in the Arctic, translates to an increase in emitted ToA longwave radiation.

My original argument about complexity remains, as the EEI has to do with the surface of the whole Earth (or top of the atmosphere), meaning that one of the mechanisms you propose could be counteracting an other, in a complex system with so many degrees of freedom; thus, I would definitely anticipate to find some non-linearities involved.

Don't get me wrong, I still find this a highly relevant and interesting research topic. I am probably not as optimistic in finding straightforward one-to-one relations.

All the best

Stamatis

Hi Stamatios,

I understand your point, and maybe it's not possible or at least very difficult to attribute any changes/intensifications/system stage changes (e.g. longer El-Ninos as the one from 1990-95) to an extreme EEI value.

In regard with the massive moist and warm air transport into the Arctic, we observed this year (seems to be much more extreme than during the last years - looked till 2018), it should increase convection in the Arctic winter atmosphere (we had e.g. rain over Greenland again during this winter), thereby transporting heat upwards in a colder and lower Arctic atmosphere which should(???) increase long-wave radiation to space.

But I will take a second look into the relevant literature e.g. Kevin E. Trenberth and citations to see what are the known main mechanisms (e.g. El-Ninos tend to reduce the EEI) as the whole subject could be of paramount importance if the EEI would further increase or not...

The current extreme EEI we had because absorbed shortwave radiation increased to the extreme. This is quite worrisome - hopefully, only SOx reductions had been responsible but I guess also a warmer ocean reducing cloud coverage - likely mutually reinforcing at least over the mid-latitudes of the NH where the shipping routes are and where those extreme marine heatwaves developed the last years.

So the future development of the EEI could become interesting if a significant cloud feedback is involved over warmer oceans (and drying out continents - in 2023 relative humidity was second lowest over the continents).

"Relative air humidity was the second lowest on record, continuing a trend towards drier average and extreme conditions. Drier-than-normal conditions prevailed nearly everywhere." https://www.globalwater.online/globalwater/report.html

At least if the system reacts to an extreme EEI we should at least see it at the TOA in the form of increased long-wave radiation - if no clear TOA signal the coming months/year(s) happens then anyway no direct response of the system. When I think of it the signal should be identifiable top-bottom.

Maybe you can plot the Ceres data in a running 12-months mean each month?

https://ceres-tool.larc.nasa.gov/ord-tool/jsp/EBAFTOA42Selection.jsp

To track the 12-month running mean each month, could show if something happens with TOA-emitted long-wave radiation. This could give an indication if a TOA EEI signal develops for example this winter because of these massive warm air intrusions. Would be highly interesting if something happens or not happens...

I attached a graph with the EEI from Berkeley Earth 2023 climate report with the 2.1 W/m2. Since then the 12-month running mean declined to 1.88 W/m2 (someone told me on X) - would like to know why - short-wave down?/long-wave up? This would be great - but if it is too much to ask I understand, but it would be very interesting.

Source: "Global Temperature Report for 2023"; https://berkeleyearth.org/global-temperature-report-for-2023/

All the best

Jan

p.s. sorry for being so long, but EEI means always Earth which makes it so complex and exciting. And the causes of the current extreme EEI also are somewhat important for this topic.

One more thing Stamatios,

what I just realized in the graph - outgoing long-wave radiation seems to react relatively direct to an increase in absorpted short-wave radiation. So this time the reaction could become much larger?

And thx a lot again for your insights on this matter!

Jan

Continue with my quest to understand the reaction of the system to an increased EEI to such exceptional levels - found a nice study that breaks it down into the details of what causes what:

My assumption that convection and higher water vapor content in the high atmosphere leads to a higher OLR was wrong - the atmosphere actually absorbs more and emits less LR in such a case.

But increased convection over the tropics strengthens the Brian Dobson circulation in the stratosphere, leading to a warmer and dryer stratosphere over the mid-to higher latitudes where the air comes down again thereby increasing top of the atmosphere OLR.

Here you can see maps breaking it down: https://www.nature.com/articles/s41612-021-00205-7/figures/2

Some text excerpts from the study:

"In the atmospheric window regions (795–970 cm−1,1070–1230 cm−1, and 2090–2170 cm−1), where the atmosphere is mostly transparent, the changes in the SOLR reflect principally the changes in the surface temperature (PDF) Trends in spectrally resolved outgoing longwave radiation from 10 years of satellite measurements."

So an increase in surface temperatures due to an extreme EEI makes sense for the system. This includes higher SST that leads to an increase in OLR.

"Convergence zones are typically associated with a strong local increase of water vapor which increases the amount of radiation absorbed. Its effect on the SOLR (known as super greenhouse effect (SGE)14,50) exceeds that of the warming of the mid-troposphere and results in a decrease of the SOLR in total."

LT - linear trend

"Conversely, subsidence zones are characterized by a drying of the air masses which translates into a decrease of the absorption (an increase of the SOLR) in the ν2 H2O band. In particular, this effect is illustrated by the large crescent-shaped positive LT observed in the tropical Western Pacific (Fig. 2d, box 6) which corresponds to a well-known region affected by severe droughts during ENSOevents51,52. Similar patterns were already observed for the longwave cloud feedbacks53, supporting our analysis on the convective processes."

So drying out continents and creating a dryer atmosphere would also make sense if the EEI increases. El-Ninos have e.g. a large effect on decreasing terrestrial precipitation. But they also increase water vapor in the upper troposphere and lower stratosphere...

Tropics and mid-latitude upper troposphere and stratosphere: "Here, the SOLR decrease are likely the result of two combined effects38: (1) the cooling of the stratosphere in link with the strengthening of the BDC and the CO2 increase, and (2) the increase of H2O concentrations in the upper troposphere that goes along with the rise in tropospheric temperature as a consequence of the Clausius-Clapeyron process. This is confirmed by the LT distribution of the strong H2Oabsorption line at 1507 cm−1 (Fig. 2e) which shows negative trends over most of the tropical and mid-latitude regions. Two regions(boxes in Fig. 2e), though, exhibit a significant positive trend. The first one is located in the Northern Pacific between 30 and 45°Nand is likely influenced by the warming of the lower stratosphere in the area (Fig. 2k). The second one, found in the Southern Pacific, is not correlated with a temperature increase in the stratosphere and might instead reflect the drying of air masses in the upper troposphere, possibly related to a local subsidence zone."

"At high latitudes, the interpretation of the LT is easier because most of the changes can be explained by a change in temperature at different altitudes. In the center of the ν2 and the ν3 CO2 band, and for the strong ν4 CH4 and ν2 H2O absorption lines (Fig. 1a, d), almost opaque to the surface emissions, the LT are strongly positive 0.2–0.4% per year) above 40°S and 55°N and reflect the warming of the stratosphere caused by a strengthening of the BDC."

This in interesting as the strengthening of the BDC is being discussed as controversial - so another sign, is that this circulation is strengthening so maybe an increasing EEI will lead to another increase of this circulation.

Article Trends in spectrally resolved outgoing longwave radiation fr...

As it seems El Ninos led to an increase in OLR La Ninas decreased it - Higher EEI favors increases in tropical convection I would summarize it. Graph from this study Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/ ). :

Article Changes in Earth’s Energy Budget during and after the “Pause...

Then I found this observational insight: "Earth’s climate is set by a balance between incoming solar and outgoing infrared radiation. The physical processes that influence this balance are complex and nonlinear, yet models and satellite measurements counterintuitively show that Earth’s infrared radiation is simply a linear function of surface temperature. Here we explain why: Linearity is due to the cancellation of two nonlinear processes and always arises in an atmosphere dominated by a condensable greenhouse gas."

This would mean an extreme EEI could lead to "direct" increases in surface temperatures, as here the OLR is increased via the OLR windows - wonder how 2024 will be...

Article Earth’s outgoing longwave radiation linear due to H 2 O gree...

Now it gets interesting - a study on the reasons for the exceptional SST increase over the North Atlantic in 2023 they connect it also with a high EEI - what I was searching for - recent signals discussed by you the experts: The regional EEI over the North Atlantic went sky high before SST's went up sky high - maybe here also a direct response of a system if the EEI gets to high over a region - so maybe regional developments of the EEI are very important to understand the consequences of an extreme EEI - here the graph under a https://creativecommons.org/licenses/by/4.0/ : Article A Glimpse into the Future: The 2023 Ocean Temperature and Se...

Another result - maybe warm air and water vapor transport into the Arctic during winter could be the exceptional reaction of an exceptional high EEI after all:

East Asia, between 30° N and 60° N

"OLR is positively correlated with total column water vapor (TCWV), air temperature (AT), and cloud top temperature (CTT), but negatively correlated with cloud top pressure (CTP). OLR has a similar spatial correlation distribution with TCWV and AT, while the spatial correlation between OLR and CTP is opposite to the first two parameters. In most parts of East Asia, the spatial correlation with CTT exceeds 0.8. The change in OLR value is affected by various meteorological parameters. In East Asia, the positive correlation between 30° N and 60° N is significantly affected by TCWV, AT, and CTT; and the negative correlation is more significantly affected by CTP. At 0–25° N, the positive correlation is significantly affected by CTP and CTT, while the negative correlation is significantly affected by TCWV and AT."

"Article A Glimpse into the Future: The 2023 Ocean Temperature and Se...

This is also important:

"The clear sky OLR (Figure 2) shows the variation of high thermal emission (yellow and red colors) linked to high surface temperatures at the equator towards low thermal emission (blue and light blue colors) linked to low surface temperatures at the poles. In the equatorial convective regions, the clear sky thermal emission is slightly reduced (light red color) due to water vapour absorption compared to the subtropical high pressure regions (yellow color)." - increase in subtropical high-pressure regions due to an extreme EEI???

"At midlatitudes, the OLR is also reduced by clouds—particularly over the oceans—as can be seen in Figure 3 (blue color). In the Northern Hemisphere, OLR minima form over ocean, and correspond more or less to the Icelandic and Aleutian low pressure systems [13]. These low pressure systems are the strongest in winter, when the ocean is warmer than the land. In the Southern Hemisphere, there exists a zonally extended low pressure system and corresponding OLR minimum over the Southern Ocean."

This could mean that the cloud feedback over marine heatwaves in the subtropical to mid-latitudes would favor an increase in OLR - what we observed to the extreme in 2023...

Furthermore, they found a clear signal of increasing OLR over the Arctic regions over the period 2001–2017 minus the mean over the period 1985–2000 - so warm air transport into the Arctic could definitely be a reaction of an extreme EEI - here the Graph Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/ ).:

Ressource: Article Decadal Changes of Earth’s Outgoing Longwave Radiation

How the spatial OLR imprint of a La Nina looks like - graph Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/ ). : Article Decadal Changes of Earth’s Outgoing Longwave Radiation