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Earths Energy Imbalance

Kevin E TrenberthNCAR

Energy on Earth

The main external influence on planet Earth is from radiation.Incoming solar shortwave radiation is unevenly distributed owing to the geometry of the Earth-sun system, and the rotation of the Earth.Outgoing longwave radiation is more uniform.

Global warming:

Under no climate change, the net flow of energy in from the sun is balanced by the net radiation out to space. ASR=OLRWith global warming there is a net energy imbalance as heat trapping gases lower OLR:Net = ASR -OLR

Trenberth et al (2009)Global temperature and carbon dioxide: anomalies through 2012Base period 1900-99; data from NOAA

A few cooler years do not mean global warming is not happening!1998 was especially warm from the major El Nino, but by cherry picking points one can infer the wrong trend (red) vs the correct one (black dashed).

132010200519982003200220062009200720042012200420012011

Has it happened before?NOAA/NCDC dataThru 20126Earths Energy Imbalance:How do we measure it?Direct measurements from space of ASR, OLR, NetTake inventory of where all the energy has goneUse climate models with specified forcingsUse atmospheric reanalyses

Not accurate enough, but good for relative changesBest, but is there some energy missing? Likely not consistent over time.Depends on how good the model and the forcings are.Useless, do not conserve energy, do not have accurate forcingsGlobal warming means more heat:Where does the heat go?Warms land and atmosphereHeat storage in the ocean (raises sea level)Melts land ice (raises sea level)Melts sea ice and warms melted waterEvaporates moisture rain storms, cloud possibly reflection to space

>90%TOA energy imbalance from CCSM4Specified radiative forcings from increased GHGs, solar, volcanoes, aerosols

Rel to ens. mean

Mo s.d. 0.62

12-mos.d.0.25 W m-20.9 W m-2

Prescribed profile in CCSM4El Chichn aerosol

Recent volcanic eruptions:Optical depth of aerosolsAdapted from Santer et al 2013

Radiative forcing (W m-2) from changes in Total Solar Irradiance from the Total Irradiance Monitor (TIM) instrument relative to a base value of TSI of 1361.14 W m-2 as 27-day running averages. The arrow at right shows the range of 0.15 W m-2. Ocean Heat Content

Balmaseda, Trenberth and Klln 2013 GRLOcean Obs

Catia DominguesArgoTemperature Obsper 1 deg square

State of the Climate 2012ECMWF Ocean Reanalysis v4: ORAS4Balmaseda et al. Quart J R Met Soc 20135 member ensemble; perturbed initial states52-year reconstruction for 1958 through 2009NEMO ocean model 1 42 level 3DvarBias corrected using Argo eraSfc fluxes from ERA, relaxed to obs SST (2-3 days)Corrected XBTs, altimetry10 day cycle

Global Ocean Heat Content

Balmaseda, Trenberth and Klln 2013 Amount of heat

Ocean Heat Content: ECMWF Reanalysis

ORAS4 vs WOA

OHC from ORAS4 and rates of change

Diff:0.21 W m-2 2000s12-mo running means

Full depth 5 member ensemble members of ORAS4 OHC in global W m-2. The ensemble mean and monthly standard deviation of CCSM4 TOA radiation RT. El Nio events are marked by the orange bars, as defined by the ONI index of NOAA. Rates of change of OHC from ORAS4ENSO in ORAS4

TOGA-TAO/Triton array was mainly established 1992-93

These are normalized to be global W m-2.The tropical Pacific Ocean firstthen the global ocean loses heat over an El Nino eventENSO and volcanic events conflatedEl Nio events occurred July 1963-January 1964 vs Agung Feb-Mar 1963; May 1982-June 1983 vs El Chichon Mar-Apr 1982; and May 1991-July 1992 vs Pinatubo June 1991. Decadal variabilityGiven the stronger and more frequent La Nia events since 1998 related to the Pacific Decadal Oscillation (PDO) a major question is what role these variations are playing?Decadal variability: PDO

Based on SST EOF analysis north of 20N in Pacific with global mean removed.Courtesy Adam PhillipsEOF= Empirical Orthogonal Function= Principal Component Analysis= Eigenvector of covariance matrix

+ve +ve -ve -ve +ve Sfc Temperatures:GISS

OHC0-100m

0-700m

Full depth

Note different color scalesSLP and surface windsERA-I

SLP and surface windsERA-I

Polar perspectiveNHSea level trend: global mean (3 mm/yr) removedGary Lagerloef 2013

Sea level trend

Merrifield 2011Linear OHC trends: ocean W m-21975-20091980s1990s2000sTotal (ocean)Global 0.47 0.030.33 0.58 0.150.41-0.26 0.13-0.181.19 0.110.840.91 W m-2 when melting ice etc included.

NOAA

UKMO

CERES vs ORAS412 month running meansCERES, ORAS4Argo=Roemmich and GilsonWOA = Levitus et al.vSch = von SchuckmannThe 12-month running men tendency from ORAS4 full depth ocean OHC tendencies are given in purple for all 5 ensemble members along with updated estimates from the World Ocean Atlas (WOA; Levitus et al. 2012) and from Argo as analyzed by Roemmich and Gilson (2011). Also shown is an estimate of the TOA imbalance based on CERES estimates (red solid lines) with 1 standard error uncertainty bounds (pink shading) for random errors based on [Loeb et al. 2012] and drift (dash/dot lines) under an assumptions of net radiative imbalance at TOA of 0.8 W m-2. Vertical orange bars indicate El Nio events and blue bars La Nia events as given by NOAAs ONI index.[ 37There is not great agreement between OHC changes and CERESORAS4 fluctuations are supported by other OHC analysesAt times there are marked significant discrepancies, notably:2002 (CERES low vs OHC)2007 (CERES high vs OHC)2009 (CERES high vs OHC)OHC vs CERESWhile the error bars are large, there appears to be either: missing energy, or mismatches in CERES vs OHCKey signals in ORAS4During the last decade, the ocean has warmed at a higher rate than in the preceding record, even when the impact of Argo is taken into account.About 30% of the warming occurs in depths below 700m. This involvement of the deep ocean in the heat uptake is unprecedented.Volcanic eruptions, ENSO and the deep ocean contribute identifiable signals to the character of ocean heat content changes.The increasing disparity of warming in different layers arises largely from changes in the surface winds, and remains even when the Argo is withdrawn.In CCSM4, sfc T rises in 5 ensemble members.Missing energy in CCSM4?

Meehl et al 2011In CCSM4, during periods with no sfc T rise, the energy imbalance at TOA remains about 1 W m-2 warming. So where does the heat go?Missing energy in CCSM4?

Meehl et al 2011

750 to 3000mIs the same as for 750 to bottom.Meehl et al 2011

Missing energy in CCSM4?Taking five ensemble members of RCP4.5 and compositing 10 distinct 10-year periods with either zero or slightly negative globally averaged temperature trend shows these time periods are characterized by a negative phase of the Interdecadal Pacific Oscillation (IPO) or La Nia.

Meehl et al 2011Earths energy imbalanceVaries from day to day with clouds and weatherVaries from year to year with ENSOAnd with sharp drops with volcanic eruptionsVaries with the PDOThe net imbalance of energy in the 2000s went from order 1 W m-2 to 0.7 W m-2 with the quiet sun and minor volcanic activityMissing energy?Some missing energy appears to be in the deep ocean and unprecedented heating of the deeper ocean is occurring.It is related to La Nia/ negative PDODuring the positive phase of PDO, more heat is deposited at shallow depths, while in ve PDO more heat is deposited below 700 m depth.Deep Doo DooThere's a clearer analysis formingOf the increase in powerful storming;But it's not just hot airAbout which we should care,For the cold ocean depths have been warming.

Lynne Page

http://limericksbylin.com/

Cover of GRL with Balmaseda et al 2013