green house gases causes imbalance in incoming solar radiation

1. Review presentation of the article:
An imperative to monitor Earth's energy imbalance, Nature Climate
Change, volume 6, pages 138–144 (2016)

2. OUTLINE
Earth’s Energy Imbalance (EEI)
EEI and Climate Sensitivity
Introduction
EEI and Climate Forcings
Evidence of EEI
Progress in monitoring EEI
Recommendations And Conclusions

3. Introduction
 The Earth's climate engine is driven from the sun's radiant energy.
 ~30% of the solar energy that comes to Earth is reflected back to space
 Energy received from the sun is mostly in the visible (or shortwave) part of the
electromagnetic spectrum.
The Earth atmosphere system
constantly tries to maintain a
balance between the energy that
reaches the Earth from the sun
And the energy that flows
from Earth back out to space
Radiation Balance of the Earth ( SOURCE: https://ceres.larc.nasa.gov/ceres_brochure.phP)

4. EEI
The components of the global flow of energy through the climate system as given by Trenberth et
al. (2009) as background values are compared with values from 8 different reanalyses for 2002--
‐2008 (except ERA-‐40 is for the 1990s), as given at lower left in the Figure, in W m -‐2 . SOURCE:
From Trenberth et al. (2011)
EEI = solar energy absorbed by the
earth - heat energy radiated from Earth
Positive EEI = future warming of Earth
Negative EEI = future cooling of the
Earth

5. EEI and Climate Sensitivity
Positive EEI = future warming of Earth
Negative EEI = future cooling of the
Earth

6. EEI and Climate forcing
EEI is influence by two categories
of climate forcings
Natural
 variations in solar output
 volcanic aerosol emissions.
 Human activities
Anthropogenic
 variations in albedo
associated with land use
changes
 various aerosol emissions
ERF = change in net downward TOA radiation after
the initial adjustment of atmospheric temperatures,
clouds and moisture, but before surface
temperatures have responded

7. Daily and monthly timescales:
 MJO. Short-term changes in
cloudiness
 The phenomena giving rise to
changes in ERF vary regionally
and over time
Interannual timescales:
ENSO plays a substantial role as
energy is taken up and stored in the ocean,
moved around and eventually dis- charged
back
into the atmosphere substantial variation of
EEI.
Longer-term
variability:
Induced through the
internal climate modes
(PDO) can temporarily
alter the EEI for several
decades
Some phenomena giving rise to changes in ERF vary regionally and over time. These variations can mask a climate change signal
Internal climate variability
source: world meteorological organisation : https://public.wmo.int/en/bulletin/predictability-
beyond-deterministic-limit

8. Evidence of EEI EEI and human activities
Positive EEI and effects (arrow- up)
Negative EEI and effects(arrow-down)
Presently, sea level is rising.
atapproximately 3 mm yr-1 with
contributions from both thermal
expansion and mass
accumulation from ice melt
Schematic representations of the flow and storage of energy in the Earth’s climate system and related consequences.
Studies have show that there has
been a multidecadal increase in
the heat content of both the upper
and deep ocean regions, which
reflects the impact of
anthropogenic warming

9. Progress in monitoring EEI
Observed climate change has been attributed to
Anthropogenic factors due to the relationship
betwen the multidecadal rise in GMSL and EEI
as seen in the rise in OHC.
However, due to the high heat
retention capacity of the oceans, the rate
of surface warming is slowed down.
Hence, (a) trends in GMST are an unreliable indicators of global warming in decadal or lesser time
scales.
(b) shows strong relatonship (indicating a reliable EEI estimate) between ocean heat content ( OHC)
and the earth system energy change.
Note: Higher relative frequencies are indicated by lighter colours

10.  Monitoring EEI requires observing systems that can reliably detect changes in EEI with an
accuracy of <0.1 W m–2 on multi annual-to-decadal timescales and <0.5 W m–2 on
subannual-to-interannual timescales.
Four approaches that can potentially be used to estimate the absolute value of EEI and its
time evolution are highlighted:
satellites to measure fluxes over TOA.
estimation of air–sea heat fluxes on annual
timescales.Atmospheric reanalyses provide using a combination of bulk formula and radia-tive
Transfer model approaches.
simulations of EEI from state-of-the-art climate
models.
However, wether combined or used separtely, all the approaches have uncertainties
and challenges.
Furthermore, absolute value of EEI using dOHC/dt can be monitored based on the
following arguments:
CMIP5 climate model simulations suggest that global OHC becomes the dominant term
in Earth’s energy budget on a timescale of about 1 year and therefore represents the
key energy storage component for EEI on annual to multidecadal timescales.

11. Major ice sheets
 Responds slowly because the penetration
of heat occurs primarily through conduc-
tion.
 change in effective heat capacity from
year to year is small.
 sea ice is important to the radiation budget
and air–sea heat exchanges locally,
however, the global impact is small
Heat capacity of some components of the climate system
The atmosphere
 Heat capacity corresponds to
that of the top 2.5 m of the ocean
(< 1% of the total open ocean
depth).
Land
 variability of surface air
temperatures over land
is a factor of two to six
times greater than that
over the oceans.

12.  An Array of autonomous profiling floats.
 High precision and accuracy
 Anchored by modern conductivity-temperature-depth
(CTD) systems
 Continuously monitors temperature and salinity of the
upper 2,000 m
GLOBAL ARGO: An improved ocean observing system
Challenges:
 Few and sparce measurements
below 2000m.
 gap in geographic coverage
under ice or polewards of 60°
latitude

13. Recommendations and conclusion
The absolute estimate of EEI and the manner it changes over time influences the
present and future estimation of a global warming climate.
 Research and development is required in satellite altimetry, GRACE and the in situ hydrographic data
processing to clearly identify the causes of errors, reduce and eliminate them.
Hence,
 Obtaining the time-derivative of OHC removes some biases but emphasizes noise, and scrutiny of
dOHC/ dt provides a way to help evaluate data products which provides background for estimating the
absolute value of EEI are advocated.
 Sustained observations from the Argo array of autonomous profiling floats and further development of
the ocean observing system to sample the deep ocean, marginal seas and sea ice regions are crucial
to refining future estimates of EEI.
 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.
 Concerted international effort is desirable for progress.
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