Satellite & Model Evidence for Global Warming Being Driven by the Pacific Decadal Oscillation Dr. Roy W. Spencer Principal Research Scientist The University of Alabama in Huntsville 10 March, 2009

Overview Satellite evidence of negative feedback has been obscured by radiative forcing due to natural cloud variations Negative feedback means that incr. CO2 is too weak to cause observed warming 7.5 Years of Terra satellite data, combined with a simple climate model, shows that the PDO can explain most of the temperature variability seen during the 20 th Century

There are TWO RADIATIVE WAYS to Cause Global Warming 1) INCREASE SOLAR RADIATION being absorbed, or 2) DECREASE INFRARED RADIATION (IR) being lost to space.

with NASA’s Aqua & Terra Satellites Observe the Behavior of TODAY’S Climate System

Traditional Way of Estimating Feedbacks From Satellite Data

d  T/dt = [Forcing – Feedback]/ C p Simple Forcing-Feedback Model of Temperature Variability Incr. CO2, aerosols, cloud changes, etc. (W m -2 ) TT ~ Ocean depth = sw + LW (W m -2 K -1 )

Simple Model Forced with Random radiative forcing (e.g. cloud variations) …leads to 100% error in diagnosed feedback! (Spencer & Braswell, Nov. 1, 2008 J. Climate) = 5 W m -2 K -1 ; 50 m mixed layer True FB Diag. FB

Even the IPCC Models Show Evidence of “radiative forcing spirals” GFDL

Simple Model Forced with Random non-radiative forcing (e.g. evap/precip. fluctuations) 0% error in diagnosed feedback Feedbacks can ONLY be measured in response to non-radiative forcing, Not radiative forcing

REAL WORLD: Both Radiative & Non-Radiative forcing …leads to an underestimate of diagnosed feedback depending upon ratio of radiative to non-radiative forcing This explains why previous satellite diagnoses of Feedback have been so variable… AND biased toward positive feedback. True FB Diag. FB

Only a FEW IPCC models show “feedback stripes” Slopes of “feedback stripes” Corresponds to long-term Feedbacks diagnosed by Forster & Taylor (2006) So, Feedback Is ONLY Indicated by Linear Striations in the Data (feedback stripes)

Terra Satellite: CERES vs. AMSU ch. 5 Suggests STRONGLY Negative Feedback Stripes (8 W m -2 K -1 )

Aqua Satellite: CERES vs. AMSU ch. 5 Suggests STRONG Negative Feedback … even without accounting for contamination by radiative forcing 5 W m -2 K -1

Strongly negative feedback (insensitive climate system) means radiative forcing from extra CO 2 too weak to cause global warming.

IF Manmade CO 2 hasn’t Caused Global Warming over the last 100 years..then what has? HOW ABOUT MOTHER NATURE.. Pacific Decadal Oscillation Global Surface Temperature Natural Cloud Variations Natural Temperature Variations ?

A Simple Model Forced by Cloud Changes Assumed Associated with the Pacific Decadal Oscillation: PDO Can explain 3/4 of 20 th Century Warming

…and Recent Satellite Data Suggests that there Indeed IS a Connection between the PDO and Cloud Variations…. PDO Index Terra Satellite Observed Cloud Changes

…and plotted here as Yearly Averages (updated thru 2007). ? 2008 ? Note that PDO forcing is actually measured…...forcing from incr. CO2 must be computed theoretically (Rad. Forcing= Total Flux minus Feedback)

The End

Natural climate variability: Partly due to Natural Cloud Variations?

Conclusions: Satellite data & simple model suggest… 1.Feedbacks are strongly negative (low climate sensitivity)  Previous feedback estimates were contaminated by radiative forcing due to cloud fluctuations  CO2 increase too weak to cause warming 2.The PDO causes natural radiative forcing of climate change  Enough to explain 75% of global warming  IPCC assumes cloud cover always remains the same  Atlantic Multidecadal Oscillation, Arctic Oscillation, El Nino, La Nina, etc. all need to be investigated as possible climate change mechanisms

1 st SATELLITE TEST OF THE CLIMATE MODELS: How they gain and lose INFRARED energy GOOD AGREEMENT Between Models & satellites for EMITTED INFRARED

2 nd SATELLITE TEST OF THE CLIMATE MODELS: How they gain and lose SOLAR energy NO AGREEMENT Between Models & satellites for REFLECTED SUNLIGHT

TOTAL SATELLITE TEST OF THE CLIMATE MODELS: How they gain and lose SOLAR+INFRARED energy. NO AGREEMENT Between Models & Satellites for REFLECTED SUNLIGHT+ EMITTED INFRARED