EEI (Earth Energy Imbalance, in W/m2) DiscussionI provide the following discussion about Earth Energy Imbalance (EEI) to help readers to better understand both that:
a) That EEI is a better measure of possible changes in climate state (see the first image), in coming decades due to a potential cascade of tipping points including ice-climate tipping points, than is GMSTA, and
b) That EEI can occur not only due to anthropogenic GHG emissions, but also from freshwater hosing events (as indicated by Hansen et al. 2016) and rapid decreases in anthropogenic aerosol emissions (see Hassan et al. 2021).
Regarding potential changes in climate state, I note that:
a) Increases in climate state are typically associated with rapid increases in climate sensitivity.
b) Consensus climate scientists who point at paleo examples of rapid changes in climate state (that occur over hundreds or thousands of years) generally do not make it clear to decision makers (for example paleo estimates of ECS are averaged together with values of ECS estimates from models and modern observation without any adjustments to account for our current situation, in CCS documents like AR5) that such examples all had much slower (twenty to thousands of time slower) rates of forcing than current rates of forcing and that the forcing in these paleo examples were all focused on one hemisphere (or the other), while current forcing is roughly acting simultaneously in both hemispheres).
c) Due to lag time in climate feedback mechanisms, society may well pass a tipping point, triggering a domino chain reaction of feedback mechanism; before, society realizes that it has triggered an irreversible tipping point.
von Schuckmann et al. (2020) quantifies the Earth energy imbalance (EEI), between 1960 and 2018, and indicates that EEI is the most critical number for representing prospects for continued global warming and climate change, even more so than GMSTA (see also the last three associated images). This work helps to bring the implications of Hansen et al. (2016) into perspective.
von Schuckmann, K., Cheng, L., Palmer, M. D., Hansen, J., Tassone, C., Aich, V., Adusumilli, S., Beltrami, H., Boyer, T., Cuesta-Valero, F. J., Desbruyères, D., Domingues, C., García-García, A., Gentine, P., Gilson, J., Gorfer, M., Haimberger, L., Ishii, M., Johnson, G. C., Killick, R., King, B. A., Kirchengast, G., Kolodziejczyk, N., Lyman, J., Marzeion, B., Mayer, M., Monier, M., Monselesan, D. P., Purkey, S., Roemmich, D., Schweiger, A., Seneviratne, S. I., Shepherd, A., Slater, D. A., Steiner, A. K., Straneo, F., Timmermans, M.-L., and Wijffels, S. E.: Heat stored in the Earth system: where does the energy go?, Earth Syst. Sci. Data, 12, 2013–2041,
https://doi.org/10.5194/essd-12-2013-2020, 2020.
https://essd.copernicus.org/articles/12/2013/2020/Abstract
Human-induced atmospheric composition changes cause a radiative imbalance at the top of the atmosphere which is driving global warming. This Earth energy imbalance (EEI) is the most critical number defining the prospects for continued global warming and climate change. Understanding the heat gain of the Earth system – and particularly how much and where the heat is distributed – is fundamental to understanding how this affects warming ocean, atmosphere and land; rising surface temperature; sea level; and loss of grounded and floating ice, which are fundamental concerns for society. This study is a Global Climate Observing System (GCOS) concerted international effort to update the Earth heat inventory and presents an updated assessment of ocean warming estimates as well as new and updated estimates of heat gain in the atmosphere, cryosphere and land over the period 1960–2018. The study obtains a consistent long-term Earth system heat gain over the period 1971–2018, with a total heat gain of 358±37 ZJ, which is equivalent to a global heating rate of 0.47±0.1 W m−2. Over the period 1971–2018 (2010–2018), the majority of heat gain is reported for the global ocean with 89 % (90 %), with 52 % for both periods in the upper 700 m depth, 28 % (30 %) for the 700–2000 m depth layer and 9 % (8 %) below 2000 m depth. Heat gain over land amounts to 6 % (5 %) over these periods, 4 % (3 %) is available for the melting of grounded and floating ice, and 1 % (2 %) is available for atmospheric warming. Our results also show that EEI is not only continuing, but also increasing: the EEI amounts to 0.87±0.12 W m−2 during 2010–2018. Stabilization of climate, the goal of the universally agreed United Nations Framework Convention on Climate Change (UNFCCC) in 1992 and the Paris Agreement in 2015, requires that EEI be reduced to approximately zero to achieve Earth's system quasi-equilibrium. The amount of CO2 in the atmosphere would need to be reduced from 410 to 353 ppm to increase heat radiation to space by 0.87 W m−2, bringing Earth back towards energy balance. This simple number, EEI, is the most fundamental metric that the scientific community and public must be aware of as the measure of how well the world is doing in the task of bringing climate change under control, and we call for an implementation of the EEI into the global stocktake based on best available science. Continued quantification and reduced uncertainties in the Earth heat inventory can be best achieved through the maintenance of the current global climate observing system, its extension into areas of gaps in the sampling, and the establishment of an international framework for concerted multidisciplinary research of the Earth heat inventory as presented in this study. This Earth heat inventory is published at the German Climate Computing Centre (DKRZ,
https://www.dkrz.de/, last access: 7 August 2020) under the DOI
https://doi.org/10.26050/WDCC/GCOS_EHI_EXP_v2 (von Schuckmann et al., 2020).
Caption for the second image: "Figure 6. Earth heat inventory (energy accumulation) in ZJ (1 ZJ = 1021 J) for the components of the Earth’s climate system relative to 1960 and from 1960 to 2018 (assuming constant cryosphere increase for the year 2018). See Sects. 1–4 for data sources. The upper ocean (0–300 m, light blue line, and 0–700 m, light blue shading) accounts for the largest amount of heat gain, together with the intermediate ocean (700–2000 m, blue shading) and the deep ocean below 2000 m depth (dark blue shading). Although much lower, the second largest contributor is the storage of heat on land (orange shading), followed by the gain of heat to melt grounded and floating ice in the cryosphere (gray shading). Due to its low heat capacity, the atmosphere (magenta shading) makes a smaller contribution. Uncertainty in the ocean estimate also dominates the total uncertainty (dot-dashed lines derived from the standard deviations (2σ) for the ocean, cryosphere and land; atmospheric uncertainty is comparably small). Deep ocean (> 2000 m) is assumed to be zero before 1990 (see Sect. 1 for more details). The dataset for the Earth heat inventory is published at the German Climate Computing Centre (DKRZ,
https://www.dkrz.de/) under the DOI
https://doi.org/10.26050/WDCC/GCOS_EHI_EXP_v2. The net flux at TOA from the NASA CERES program is shown in red (
https://ceres.larc.nasa.gov/data/, last access: 7 August 2020; see also for example Loeb et al., 2012) for the period 2005–2018 to account for the golden period of best available estimates. We obtain a total heat gain of 358 ± 37 ZJ over the period 1971–2018, which is equivalent to a heating rate (i.e., the EEI) of 0.47±0.1 W m−2 applied continuously over the surface area of the Earth (5.10×1014 m2 ). The corresponding EEI over the period 2010–2018 amounts to 0.87±0.12 W m−2 . A weighted least square fit has been used taking into account the uncertainty range (see also von Schuckmann and Le Traon, 2011)."
Caption for the third image: "Figure 7. Overview on EEI estimates as obtained from previous publications; references are listed in the figure legend. For IPCC AR5, Rhein et al. (2013) is used. The color bars take into account the uncertainty ranges provided in each publication, respectively. For comparison, the estimates of our Earth heat inventory based on the results of Fig. 6 have been added (yellow lines) for the periods 1971–2018, 1993–2018 and 2010–2018, and the trends have been evaluated using a weighted least square fit (see von Schuckmann and Le Traon, 2011, for details on the method)."
Caption for the fourth image: "Figure 8. Schematic presentation on the Earth heat inventory for the current anthropogenically driven positive Earth energy imbalance at the top of the atmosphere (TOA). The relative partition (in %) of the Earth heat inventory presented in Fig. 6 for the different components is given for the ocean (upper: 0–700 m, intermediate: 700–2000 m, deep: > 2000 m), land, cryosphere (grounded and floating ice) and atmosphere, for the periods 1971–2018 and 2010–2018 (for the latter period values are provided in parentheses), as well as for the EEI. The total heat gain (in red) over the period 1971–2018 is obtained from the Earth heat inventory as presented in Fig. 6. To reduce the 2010–2018 EEI of 0.87 ± 0.12 W m−2 towards zero, current atmospheric CO2 would need to be reduced by −57 ± 8 ppm (see text for more details)."
So energy imbalance is presently +0.87 W/m2/K. How much more does the Earth have to warm to wipe out that imbalance? That connection between energy imbalance and temperature is known as the climate sensitivity.
If climate sensitivity is ~0.75 K/(W/m2) (corresponding to ~3°C for doubled CO2), then that tells us that we need to warm the climate about 1°C *more* to reach energy balance, at which point the Earth will be in energy balance.
Except it won't be. We're still emitting carbon dioxide, so by the time the planet has warmed enough to wipe out the +0.87 W/m2 of energy imbalance that we measure today, we'll have emitted a whole lotta CO2 that will have increased the energy imbalance.
See also:
Loeb, N.G. et al. (15 June 2021), "Satellite and Ocean Data Reveal Marked Increase in Earth's Heating Rate", Geophysical Research Letters,
https://doi.org/10.1029/2021GL093047&
Title: "Joint NASA, NOAA Study Finds Earth's Energy Imbalance Has Doubled"
https://www.nasa.gov/feature/langley/joint-nasa-noaa-study-finds-earths-energy-imbalance-has-doubledExtract: "Researchers have found that Earth’s energy imbalance approximately doubled during the 14-year period from 2005 to 2019.
"It's likely a mix of anthropogenic forcing and internal variability," said Loeb. "And over this period they're both causing warming, which leads to a fairly large change in Earth's energy imbalance. The magnitude of the increase is unprecedented." …
The study does conclude, however, that unless the rate of heat uptake subsides, greater changes in climate than are already occurring should be expected."
See also:
Title: "Don’t Worry about CO2, Worry about the Earth’s ‘Energy Balance’ -
The “most fundamental” climate metric takes a troubling turn"
By Chelsea Harvey, E&E News on June 16, 2021
https://www.scientificamerican.com/article/dont-worry-about-co2-worry-about-the-earths-energy-balance/Extract: "The researchers also conducted an extra analysis to figure out why the imbalance is quickly worsening. Greenhouse gases in the atmosphere are clearly a major driver. But as the planet has warmed, it’s triggered other feedback cycles that have further increased the imbalance.
Melting ice is one of these feedbacks.
…
It’s a reminder that not all the consequences of climate change are linear. The climate system is full of feedback loops, which can quicken the speed at which the planet warms and changes.
If the Earth’s energy imbalance continues to worsen, the researchers warned, then they would expect “even greater changes in climate in the coming decades.”"
