C LOUD R ADIATIVE K ERNELS : C LOUDS IN W/m 2 with T. Andrews, J. Boyle, A. Dessler, P. Forster, P. Gleckler, J. Gregory, D. Hartmann, S. Klein, R. Pincus, K. Taylor, M. Webb, P. Yang, Y. Zhang, C. Zhou ISCCP at 30 Conference | 24 April 2013 This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA IM release #LLNL-PRES Mark D. Zelinka

Using Fu-Liou radiative transfer model, we compute sensitivity of TOA radiation to cloud fraction changes in each ISCCP CTP- τ bin: Cloud-induced radiative flux anomalies: Cloud Radiative Kernels Perturbed minus unperturbed climate GCM (ISCCP simulator) minus ISCCP observations  Steve Klein talk Other satellite minus ISCCP observations  C. Stubenrauch talk O 3 hole simulations  Kevin Grise talk Enhanced CO 2 simulations Observed climate variability (ENSO) Enhanced aerosol simulations

CTP (hPa) CTP (hPa) CTP (hPa) LW SW Net W m -2 % -1 Global Annual Mean Cloud Kernels W m -2 % -1 Optical Depth Zelinka et al. (2012a) J. Climate

Using Fu-Liou radiative transfer model, we compute sensitivity of TOA radiation to cloud fraction changes in each ISCCP CTP- τ bin: Cloud-induced radiative flux anomalies: Cloud Radiative Kernels Perturbed minus unperturbed climate GCM (ISCCP simulator) minus ISCCP observations  Steve Klein talk Other satellite minus ISCCP observations  C. Stubenrauch talk O 3 hole simulations  Kevin Grise talk Enhanced CO 2 simulations Observed climate variability (ENSO) Enhanced aerosol simulations

Using Fu-Liou radiative transfer model, we compute sensitivity of TOA radiation to cloud fraction changes in each ISCCP CTP- τ bin: Cloud-induced radiative flux anomalies: Cloud Radiative Kernels Perturbed minus unperturbed climate GCM (ISCCP simulator) minus ISCCP observations  Steve Klein talk Other satellite minus ISCCP observations  C. Stubenrauch talk O 3 hole simulations  Kevin Grise talk Enhanced CO 2 simulations Observed climate variability (ENSO) Enhanced aerosol simulations

Control Clouds Perturbed Clouds x Cloud Radiative Kernels at each location and month to compute cloud-induced TOA radiation anomalies…. Satellite Simulator Cloud Histograms Each cloud fraction shown is “visible” from space (i.e., the non-overlapped cloud fraction) Zelinka et al., J. Climate (2012a) CTP (hPa) CTP (hPa) CTP (hPa) Cloud Fraction τ %

1xCO % 2xCO % Change -0.5 % K -1 τ LW 0.20 Wm -2 K -1 SW 0.37 Wm -2 K -1 Net 0.58 Wm -2 K -1 LW SW Net Cloud Radiative Kernel τ τ Control Climate Clouds Perturbed Climate Clouds CTP (hPa) CTP (hPa) CTP (hPa) Zelinka et al., J. Climate (2012a) % Wm -2 % -1

Cloud Fraction Cloud-Induced Rad. Anomalies 1xCO % 2xCO % Change -0.5 % K -1 LW 0.20 Wm -2 K -1 SW 0.37 Wm -2 K -1 Net 0.58 Wm -2 K -1 LW SW Net Control Climate Clouds Perturbed Climate Clouds CTP (hPa) CTP (hPa) CTP (hPa) ττ Zelinka et al., J. Climate (2012a) % Wm -2 Plot ∆R C against ∆T S  slope = feedback

9 Cloud-induced radiation anomalies (Positive = heating) LWSW ∆T sfc Zelinka et al., J. Climate (in press) y = 0.76x – 0.01 y = 0.29x y = 0.06x – 0.04 y = 0.37x – 0.16 y = -0.04x – 0.15 y = -0.30x y = 0.28x – 0.57 y = -0.16x y = 0.03x y = 0.21x – 0.25

Δτ: 2.0 % K -1 Cold clouds get brighter What happens to clouds as the planet warms in climate models? POSITIVE NEGATIVE Implied Feedback ….but the devil is in the details… Δ CTP: hPa K -1 Δ Total Cloud Frac.: % K -1 Clouds go away Zelinka et al., J. Climate (in press) Clouds rise

Total Amount Altitude Optical Depth 11 As in CMIP3, biggest inter-model spread in LW and SW comes from high clouds, but biggest inter-model spread in net comes from low clouds As the planet warms, clouds become fewer, higher, and thicker  The SW cloud feedback is small because fewer oppose thicker The net cloud amount and altitude feedbacks are robustly positive Zelinka et al., J. Climate (in press) Global Mean Cloud Feedbacks

Cloud Feedback + Adjustment Increase CO 2 Planet warms Radiatively heat planet Cloud properties change The Climate System Rapid cloud adjustment

13 Cloud-induced radiation anomalies xRadiation anomalies from fixed SST runs with 4xCO 2 imposed (Positive = heating) LWSW ∆T sfc Zelinka et al., J. Climate (in press)

Total Amount Altitude Optical Depth 14 Immediately upon CO 2 quadrupling, clouds become fewer, higher, and thinner  the LW cloud adjustment is small because fewer/thinner oppose higher Thinner & fewer act together to bring about a big reduction in reflected SW Zelinka et al., J. Climate (in press) Global Mean Rapid Cloud Adjustments

Using Fu-Liou radiative transfer model, we compute sensitivity of TOA radiation to cloud fraction changes in each ISCCP CTP- τ bin: Cloud-induced radiative flux anomalies: Cloud Radiative Kernels Perturbed minus unperturbed climate GCM (ISCCP simulator) minus ISCCP observations  Steve Klein talk Other satellite minus ISCCP observations  C. Stubenrauch talk O 3 hole simulations  Kevin Grise talk Enhanced CO 2 simulations Observed climate variability (ENSO) Enhanced aerosol simulations

∆log(τ cloud ) CanESM2 HadGEM2-A MRI-CGCM3 MIROC5 Year 2000 sulfate aerosols, all else held at preindustrial

SW Indirect Effect Components HadGEM2-A Total Optical Depth (“Twomey”) Amount (“Lifetime”) Wm -2

Using Fu-Liou radiative transfer model, we compute sensitivity of TOA radiation to cloud fraction changes in each ISCCP CTP- τ bin: Cloud-induced radiative flux anomalies: Cloud Radiative Kernels Perturbed minus unperturbed climate GCM (ISCCP simulator) minus ISCCP observations  Steve Klein talk Other satellite minus ISCCP observations  C. Stubenrauch talk O 3 hole simulations  Kevin Grise talk Enhanced CO 2 simulations Observed climate variability (ENSO) Enhanced aerosol simulations

CMIP3 CMIP5 Cloud-Induced Reflected SW Biases w.r.t. ISCCP Wm -2 CMIP3 CMIP5

Metrics of model performance Individual modeling centers show big improvement between old and new versions (arrows point left) Canada Germany Japan U.K. U.S. (NCAR) U.S. (GFDL) Model Mean Klein et al., J. Geophys. Res. (in press)

Using Fu-Liou radiative transfer model, we compute sensitivity of TOA radiation to cloud fraction changes in each ISCCP CTP- τ bin: Cloud-induced radiative flux anomalies: Cloud Radiative Kernels Perturbed minus unperturbed climate GCM (ISCCP simulator) minus ISCCP observations  Steve Klein talk Other satellite minus ISCCP observations  C. Stubenrauch talk O 3 hole simulations  Kevin Grise talk Enhanced CO 2 simulations Observed climate variability (ENSO) Enhanced aerosol simulations

Short-term cloud feedback Understanding contributions of different cloud types to observed short-term cloud feedback (Zhou, et al., J. Climate, in press) All Clouds hPa Clouds hPa Clouds ∆T S 22

Using Fu-Liou radiative transfer model, we compute sensitivity of TOA radiation to cloud fraction changes in each ISCCP CTP- τ bin: Cloud-induced radiative flux anomalies: Cloud Radiative Kernels Perturbed minus unperturbed climate GCM (ISCCP simulator) minus ISCCP observations  Steve Klein talk Other satellite minus ISCCP observations  C. Stubenrauch talk O 3 hole simulations  Kevin Grise talk Enhanced CO 2 simulations Observed climate variability (ENSO) Enhanced aerosol simulations

Conclusions Cloud kernels are a useful tool for calculating the radiative impact of CTP-τ segregated cloud anomalies, which has many applications: GCM cloud feedbacks and rapid adjustments – Rapid response to CO 2 : Clouds become fewer, higher, and thinner; thus they act to increase the CO 2 radiative forcing – As planet warms: Clouds become fewer, higher, and thicker; net cloud feedback is positive in all but one model Observed short-term cloud feedback – Insignificant global mean net cloud feedback comes from robust but counter-acting feedbacks due to high vs. low clouds GCM cloud-radiation biases – Current GCMs still get TOA budget right by simulating clouds that are too few and too bright, but huge improvement over previous generation of GCMs GCM aerosol indirect effects – Indirect effect (IE) dominates over direct effect – Albedo IE dominates over amount IE; large inter-model spread Ozone hole “indirect effect” (ozone – dynamics – clouds – radiation) – Stay tuned for Kevin Grise’s talk

Thank you!

26 Zelinka, et al., J. Climate (in press) Latitude ΔRH (%, absolute) SRES A2: 2090s minus 2000s T sfc -Mediated Cloud Changes

CMIP3 CMIP5 Cloud Fraction Biases

Δτ: -4 % Cloud albedo decreases POSITIVE Implied Radiative Impact Δ Total Cloud Frac.: % Clouds go away Zelinka et al., J. Climate (in press) Δ CTP: hPa What happens to clouds immediately upon quadrupling CO 2 ? Clouds over land rise