THE EARTH ENERGY BALANCE OVERVIEW & CHALLENGES
Karina von Schuckmann
Mercator Ocean international, France
Swiss National GAW/GCOS Symposium, 13-14 September 2021, Bern
The state, variability and change ofthe climate are to a large extentdriven by energy transfer betweenthe different components of theEarth's system.
Energy flows alter clouds, andweather and external and internalclimate forcing can temporarily alterthe Earth energy balance forperiods of days to several decades.
EARTH ENERGY BALANCE
The Earth energy balance is one of the most fundamental condition for making planet Earth conducive to sustaining life.
Earth’s energy budget is determined by the main flows of energy into and out of the Earth system.
von Schuckmann at al., 2016
Perturbations of the equilibrium Earth energy budget arise from internal or external climate variations and can create a postive or
negative Earth energy imbalance, manifested as a radiativeflux imbalance at the top of the atmosphere
EARTH ENERGY BALANCE at the top of the atmosphere
• Changes in atmospheric composition and land use (e.g. anthropogenic GHG emissions & emissions of aerosols and their precursors) affect climate through perturbations to Earth’s top-of-atmosphere energy budget
• How the climate system responds to a given forcing (equilibrium climate sensitivity & transient climate response) is determined by climate feedbacks associated with physical, biogeophysical and biogeochemical processes.
EARTH ENERGY BALANCE: Climate forcing
Variations of Earth’s energy budget are determined on how energy flows govern the climate response to a radiative forcing.
Gulev et al., 2021 (IPCC AR6, Chapter 2)
Understanding of changes in the Earth’s energy flows helps understanding of the main physical processes driving climate
variability & change
Dieng et al., 2017
d(OHC)/dt (in situ)d(OHC)/dt (satellite)Net flux at TOA (satellite)
EARTH ENERGY BALANCE: Climate forcing
Gulev et al., 2021 (IPCC AR6, Chapter 2)
Effective radiative forcing Earth energy imbalance
Subseasonal to decadal Decadal and longer
Changes in solar output (+/-) Milankovitch cycle (+/-) Human induced changes (+)
Climate variability (+/-)(e.g. ENSO, PDO)
Large volcanic eruptions (-)
Human-caused net positive radiative forcing causes an accumulation of additional energy (heating) in the climate system.
EARTH ENERGY BALANCE: Current status as assessed in IPCC AR6
Forster et al., 2021 (IPCC AR6, Chapter 7)
Estimates of the net cumulative energy change (ZJ = 1021 Joules) for the period 1971–2018
Heat inventory
Ener
gyC
hang
e (Z
J)
Radiative forcing
von Schuckmann et al., 2020
EARTH ENERGY BALANCE: Current status
IPCC AR6: • 1971–2006: 0.50 [0.32 to 0.69] Wm2
• 2006–2018: 0.79 [0.52 to 1.06] Wm2
Evolution of the Earth energy imbalance over time – published estimates
von Schuckmann et al., 2020
IPCC AR6 (1971–2018):
• Ocean: 91% • Land: 5%• Cryopshere: 3%• Atmosphere: 1%
Ocean heat uptake is by far the largest contribution, followed by land heating, melting of ice and warming of the atmosphere
EARTH ENERGY BALANCE: Earth heat inventory
Josey et al., 2015
turbulent
radi
ativ
e
Earth surface budget
Radiation at TOA
Climate modelsEarth heat inventory
EARTH ENERGY BALANCE: How to monitor & evaluate?
Loeb et al., 2021
fundamental test of climate models and their
projectionsForster et al., 2021 (IPCC AR6, Chapter 7)
Josey et al., 2015
turbulent
radi
ativ
e
Earth surface budget
Radiation at TOA
Climate modelsEarth heat inventory
EARTH ENERGY BALANCE: How to monitor & evaluate?
Loeb et al., 2021
fundamental test of climate models and their
projectionsForster et al., 2021 (IPCC AR6, Chapter 7)
EARTH ENERGY BALANCE: The global mean energy balance at the Earth’s surface
OLR: outgoing longwave rad.DLR: downward longwave rad.
ULR: upward longwave rad.OSR: outgoing solar rad.
DSR: downward solar rad.USR: upward solar rad.
P: precipitation rateSH: sensible heat flux
E: latent heat flux
after L’Ecuyer et al. 2015,updated based on Loeb et al. 2018 and Kato et al. 2018
Estimates of the current state of the energy cycle
(Wm-2)
ALL-SKY
The unconstrained view of the Earth’s energy budget does not balance
L’Ecuyer et al. (2015)
EARTH ENERGY BALANCE: The global mean energy balance at the Earth’s surface
(Wm-2)
Earth’s energy budget with balance constraints imposed.
NEWS OriginalNEWS ConstrainedWm-2
341
17
184
333
239
Trenberth et al. (2009)
23
80
102
396
80
0.9
340 ± 0.1
24 ± 7
188 ± 7
346 ± 9
240 ± 3
Stephens et al. (2012)
23 ± 388 ± 10
100 ± 2
398 ± 5
0.6
88 ± 10
340
21
185
342
240
Wild et al. (2015)
2485
100
398
82
0.6
EARTH ENERGY BALANCE: The global mean energy balance at the Earth’s surface
ALL-SKY
Earth Energy Budget closure at the surface: an integrated way forward
The global mean energy balance at the Earth’s surface: estimates of the current state of the energy cycle …
… subject of vigorous research for more thana century
… central for accurate observationally basedbenchmarks of energy flows to evaluate andrefine model physics
… Satellite observations with improvedcalibration and increased spatial and temporalresolution have played a central role in refiningreconstructions of Earth’s energy balance
… growing network of surface-basedmeasurements has provided substantiallybetter constraints
… improvements in global atmosphericreanalyses through both increased resolutionand the ability to assimilate extensive ground-based and satellite observations
Together, these advances have enabled new reconstructions of energy balance on combinationsof in situ observations, satellite
datasets, and reanalyses bring together
complementary expertise and datasets to provide a
comprehensive view of the Earth surface energy budget
(e.g. NASA NEWS type)
EARTH ENERGY BALANCE: The global mean energy balance at the Earth’s surface
Key issues:
• Improve uncertainty understanding of the 10 Wm-2 to 15 Wm-2 global surfaceenergy balance residual (e.g. reduce the uncertainty in surface energy fluxes by reducinguncertainties in near surface properties (e.g. temperature, water vapor, wind speed).
• Investigation of surface energy budget at smaller temporal and spatial scales(e.g. monthly, regional)
• Adress and specify accuracy and stability requirements, which can widely varydepending on applications (climate change, regional, …), and by flux type(radiative fluxes & turbulent fluxes) in situ surface observations and surfaceflux data products (GCOS)
• Horizontal energy transport to achieve regional energy budget closure for theregional energy budget
Assessments & intercomparisons activities are taking place underGEWEX/GDAP.
EARTH ENERGY BALANCE: Key issues for the Earth surface budget: key issues
Josey et al., 2015
turbulent
radi
ativ
e
Earth surface budget
Radiation at TOA
Climate modelsEarth heat inventory
EARTH ENERGY BALANCE: How to monitor & evaluate?
Loeb et al., 2021
fundamental test of climate models and their
projectionsForster et al., 2021 (IPCC AR6, Chapter 7)
EARTH ENERGY BALANCE: The Earth heat inventory
EEI can best be estimated from the Earth heat inventory, complemented byradiation measurements from space.
Combining multiple measurements in an optimal way holds considerable promise for estimating EEI and thus assessing the status of global climate change,
improving climate syntheses and models, and testing the effectiveness of mitigation actions. Progress can be achieved with a concerted international effort.
von Schuckmann at al., 2016
LAND OCEAN
CRYOSPHEREATMOSPHERE
HEAT
WHERE DOES THE ENERGY GO?
THE EARTH HEAT INVENTORY
HEAT AVAILABLE TO WARM LAND
ATMOSPHERIC HEAT CONTENTHEAT AVAILABLE TO MELT ICE
OCEAN HEAT CONTENT
Total heat gain of 358 ±37 ZJ during 1971-2018
HOW MUCH? WHERE?
89% OCEAN
6% LAND
4% CRYOSPHERE1% ATMOSPHERE
WHERE DOES THE ENERGY GO?
von Schuckmann et al., 2020
THE EARTH HEAT INVENTORY
Total heat gain of 358 ±37 ZJ during 1971-2018
HOW MUCH? WHERE?
89% OCEAN
6% LAND
4% CRYOSPHERE1% ATMOSPHERE
RATE OF CHANGE IN TIME
1971-2018: 0.47 ± 0.1 W/m2
2010-2018: 0.87 ± 0.1 W/m2
WHERE DOES THE ENERGY GO?
von Schuckmann et al., 2020
THE EARTH HEAT INVENTORY
The various facetsand impacts of
observed climatechange arise due to
the positive EEI, which thus representsa crucial measure of
the rate of climatechange.
The EEI is the most critical number defining the prospects for continued global warming and climate change. 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
The EEI is the portion of the forcing that the Earth has not yet been responded to(F- ∆T/S)
How much heat is ‘in the pipeline’ ?
von Schuckmann et al., 2020
THE EARTH HEAT INVENTORY: WHY SHOULD WE CARE?
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,
as well as to establish an international framework for concerted multi-disciplinary
research of the Earth heat inventory
THE EARTH HEAT INVENTORY: FINAL COMMENTS
Major challenges / recommendations …. … Further unravel underlying uncertainties, identify biases and further advance on
observing system recommendations to fill critical measurement gaps
… Further foster multi-product approaches & physical budget constraints
… Advance on the role of internal vs. external variability
… Unravel heat re-distribution within different Earth system components at differenttime scales
… Explore potential new approaches to complement and cross-validate the Earthheat inventory approach
Josey et al., 2015
turbulent
radi
ativ
e
Earth surface budget
Radiation at TOA
Climate modelsEarth heat inventory
EARTH ENERGY BALANCE: How to monitor & evaluate?
Loeb et al., 2021
fundamental test of climate models and their
projectionsForster et al., 2021 (IPCC AR6, Chapter 7)
The Earth energyimbalance budget
constraint
EARTH ENERGY BALANCE: The Earth energy imbalance (EEI)
Palmer and McNeal, 2014
Trend length [month]
Cor
rela
tion
Correlation of modelled EEI & OHC
Change in TOA net radiation and rate of global ocean heat storage from independent global climate observing systems should be in phase and of the same magnitude on annual and longer time scales (e.g. Hansen et al., 2005, 2011; Loeb et al., 2012; Palmer &
McNeal, 2014; von Schuckmann et al., 2016).
All other forms of heat storage are factors of 10 smaller at that time scale (e.g. Hansen et al., 2005, 2011; Trenberth et al., 2009; Loeb et al., 2012, Palmer and Mc Neal 2014, von Schuckmann et al., 2016).
Cheng et al., 2017
EARTH ENERGY BALANCE: The Earth energy imbalance (EEI) budget constraint
Loeb et al., 2021
Comparing net flux at TOA & Earth heat inventory
The GCOS components for the Earth energy imbalance budget constraint
The Earth energyimbalance (EEI) physical
budget constraint: a fundamental tool for
evaluation of the EEI and its uncertainties from the
underlying GCOS components
Heat has sequestered down into deeper ocean layers over the past 5 decades
Over the past decade (2010-2018), ocean warming rates have reached record values of 0.7 ± 0.1 (1.3 ± 0.3) W/m2 for the upper 700
(2000m) depth of the near-global (60°S-60°N) ocean EEI (1971-2018): 0.47 ± 0.1 W/m2; (2010-2018): 0.87 ± 0.12 W/m2
von Schuckmann et al., 2020
EARTH ENERGY BALANCE: Changes of the Earth energy imbalance (EEI)
EARTH ENERGY BALANCE: Changes of the Earth energy imbalance
Lui et al., 2020
Loeb et al., 2021
Kramer et al., 2021
How and why did EEI change over the past decade?
All-sky instantaneaous radiative forcing has increased by 0.53 ± 0.1 W/m2 from 2003 through 2018, accounting for a positive trend in the total planetary radiative imbalance due to a combination of rising concentrations of well-mixed GHG and recent reductions in aerosol emissions
Decadal increase in EEI from mid-2005 to mid-2019 of 0.5 ± 0.1 W/m2 from decreasedreflection of energy back into space by clouds& sea-ice, and increases in well-mixed GHG and water vapor.
EEI increase from 0.1 ± 0.61 W/m2 (1985-1999) to 0.62 ± 0.1 W/m2 (2000-2016), linked to changes in surface heat flux, planetary heat re-distribution and changes in ocean heat storage
W/m2
(rel. to 2001-2005)
A positive EEI of 0.2 W/m2 (for 10,000 y) during the deglaciation brought the climatesystem from the last ice age into the Holocene warm period.
The EEI varied significantly during thisperiod, with values up to 0.4 Wm−2 duringtimes of substantially reduced Atlantic Meridional Overturning Circulation net changes in ocean heat uptake, likely due to rapid changes in North Atlantic deep water formation and their impact on the global radiative balance,
changes in cloud coverage, albeit uncertain, may also factor into the picture.
Baggenstos et al., 2019
Reconstruction (noble gas) of the radiative imbalance for the last deglaciation, 20,000 to 10,000 y ago. importance of internal variability in the
Earth’s energy budget.
EARTH ENERGY BALANCE: Changes of the Earth energy imbalance (EEI)
Josey et al., 2015
turbulent
radi
ativ
e
Earth surface budget
Radiation at TOA
Climate modelsEarth heat inventory
EARTH ENERGY BALANCE: How to monitor & evaluate?
Loeb et al., 2021
fundamental test of climate models and their
projectionsForster et al., 2021 (IPCC AR6, Chapter 7)
EARTH ENERGY BALANCE: The Earth heat inventory in CMIP5
radiative imbalance at TOA Earth heat inventory Ocean heat content
Simulated heat storage (1972–2005) from 30 CMIP5 GCM historical simulations
Assessment of the Earth heat inventory within CMIP5 historical simulations
The representation of terrestrial ice masses & the continental subsurface, as well as the response of each model to the external forcing, should be improved
in order to obtain better representations of the Earth heat inventory and the partition of heat among climate subsystems in global transient climate models
in comparison withrecent observations, the CMIP5 ensemble
overestimates the ocean heat content and underestimatesthe continental and
cryosphere heatstorage
Cuesta-Valero et al., 2021
von Schuckmann et al., 2020
Church et al., 2011
EARTH ENERGY BALANCE: The global energy balance in CMIP6
Wild, 2020
Global energy balance components are in better agreement with recentreference estimates compared to earlier model generations, particularly
for shortwave clear-sky budgets
However, substantial inter-model spread in the
simulated global meanlatent heat fluxes are present in the CMIP6
models, exceeding 20% (18 Wm−2)
CMIP6 has become the first model generation that largely remediates long-standing model deficiencies: overestimation in surface downward shortwave compensated by
an underestimation in downward longwave radiation (multi-model mean)
EARTH ENERGY BALANCE: Key messages
• The Earth energy balance is one of the most fundamental condition for making planet Earth conducive to sustaining life.
• Understanding of changes in the Earth’s energy flows helps understanding of the main physical processes driving climate variability & change
• The EEI is the most critical metric that the scientificcommunity and public must be aware as the measure for prospects of continued global warming and climate change and as the measure of how well the world is doing in the task of bringing climate change under control
• The EEI has increased over the past decade, and drivers for this change of anthropogenic and natural origin needfurther evaluation
EARTH ENERGY BALANCE: Synthesis of future opportunities
Advancements in uncertainty understanding & specify accuracyand stability requirements for all Earth energy budgetapproaches
Further advance on observing system recommendations, and fillcritical measurement gaps under a maintained GCOS
Further advance on the simulation of the global energy balance Investigations at different temporal and spatial scale through
regional energy budget closure approach Further advance on the role of planetary heat re-distribution and
their role in the Earth energy budget Further foster multi-product approaches & physical budget
constraints through concerted multi-disciplinary internationalcollaboration