# Presentation: 161187

## U.S. Modeling Contributions to the IPCC Fourth Assessment Report (AR4) 

- Gerald A. Meehl
-  NCAR
-  Boulder, CO

## The IPCC AR4 has motivated the formulation of the largest international global coupled climate model experiment and multi-model analysis effort ever attempted, and is being coordinated by the WCRP/CLIVAR Working Group on Coupled Models (WGCM) Climate Simulation Panel 

- Seventeen modeling groups from 10 countries around the world are participating with 23 models;  considerable resources have been devoted to this project;
- PCMDI has taken on the considerable task of collecting, archiving and making available the model data;  ~27 TeraBytes of model data archived so far

## Three global coupled climate modeling groups from the U.S. have made major contributions to the AR4: 1)  Running the extensive set of model experiments with multi-member ensembles

- 2) Publishing scientific results from the experiments
- GFDL (NOAA)
- GISS (NASA)
- NCAR-CCSM (NSF-DOE)
- The Climate Model Evaluation Project (CMEP) has also  supported analyses of the U.S. model data for IPCC

## Participating AOGCMs (23 models from 17 institutions in 10 countries)

- x
- x
- x
- x
- x
- x
- x

## Ensemble members

- x
- x
- x
- x
- x
- x
- x

## Climate change commitment in the NCAR CCSM3 and PCM

- At any point in time, we are committed to additional warming and sea level rise from the radiative forcing already in the system.
- Warming stabilizes after several decades, but sea level from thermal expansion continues to rise for centuries.
- (Meehl et al., 2005:  How much more warming and sea level rise?  *Science*, **307**, 1769—1772)

##      Ocean Heat Uptake in GISS model

-      Ocean Heat Uptake in GISS model

- (Hansen, J. and co-authors, 2005:  Earth's Energy Imbalance: Confirmation and Implications. *Science*, **308**: 1431-1435)

## Summer Drying in GFDL model

- (Findell, K. L., and T. L. Delworth, 2005: A modeling study of dynamic and thermodynamic mechanisms for summer drying in response to global warming. *Geophysical Research Letters*, **32**, L16702, doi: 10.1029/2005GL023414.)

## Slide 9

-                                                     b)
-  c)                                                      d)

- 21 AOGCMs, 2080-99 compared to 1980-99, SRES A1B, common 5° lat-lon grid

- (Furrer et al., 2005)

## Results from analyses of the multi-model dataset were presented by 125 scientists at a workshop convened by US CLIVAR and hosted by IPRC (Univ. of Hawaii) March 1-4, 2005, and are feeding directly into the AR4 assessment process

- Over 200 papers have been submitted to peer-reviewed journals with results from multi-model analyses for assessment in the IPCC AR4
- This is more than double the most optimistic estimate for participation
- To date, there are over 400 analysis projects registered at PCMDI, with about three more being added each week

## U.S. CLIVAR Climate Model Evaluation Project (CMEP)

-  US CLIVAR recommended that NSF, NOAA, NASA, and DOE have a program to evaluate US coupled climate model simulations of 19th and 20th century
-  61 proposals submitted - 19 funded
-  List of awards and abstract found at: _[www.usclivar.org/science.html](http://www.usclivar.org/science.html)_
- CMEP IPCC AR4 Workshop hosted by the International Pacific Research Center (IPRC) at the Univ. of  Hawaii...about 150 participants

## CMEP results: NAO Variability

- NAO variability is tracked using the leading EOF of 850mb heights in the Atlantic sector
- Models are able to generate the salient features of the NAO pattern. The observed pattern exhibits no Pacific connections, but the GFDL pattern does. The southern cell is eastward shifted in CCSM3
- Robust surface temperature signals are produced over northeastern North America and northern Europe and Asia in all models. Distribution of the warming signal over US is more varied, though
- Precipitation anomalies over the Atlantic, reflecting meridional stormtrack displacement, are generally well captured in all models. Positive rainfall anomalies are placed a bit too eastward in CCSM3 and a bit too westward in the GISS C4x3 model.
- NAO related zonal-mean zonal wind anomalies, having a dipole structure in the midlatitudes, are realistically modeled in the GFDL, CCSM3 and PCM runs; they serve to broaden the jet in all cases; connections to the lower stratosphere are also well modeled   (Nigam)

-                                    (S. Nigam)

- CMEP Results

## (Santer et al., 2005, Science) obs and 49 realizations from 19 AOGCMs

- Tropics
- 20N-20S

- Monthly

- 1979-99

- CCSP 1.1

## Conclusions

- 1. The U.S. modeling centers (GFDL, GISS, and NCAR-CCSM) have all made significant contributions in terms of running the model experiments and analyzing results from their models for publication and assessment in the AR4
- PCMDI has taken on the formidable task of collecting, archiving and making available the multi-model data; 27 terabytes archived, over 400 registered analysts, more than 200 papers submitted
- CMEP has provided funding for 19 U.S. projects to analyze the output from the U.S. models
- The model data have been used and will continue to be used in support of the CCSP reports and further CMEP analyses (recommended by US CLIVAR)

## IPCC AR4 ENSO Events

*A*.*Capotondi*

- OBS

- CCSM

- GFDL

- GISS

- A. Solomon

- CMEP Results

**Notes:**
Do not copy or cite
NONE of the models replicate ENSO’s terribly well. CCSM ENSO’s too frequent; GFDL La Nino’s too frequent and strong, GISS too weak. 

Overlay: 20-yr running average shows that observed warming trend seen in all models BUT GFDL

(Solomon)Coupled climate model simulations of the late 19th-20th century accurately simulate the observed increase in tropical SSTs since the 1970s. However, the rapid increase in the 1980’s is not uniformly reproduced. In this study we define climate mean as the average over the 1958-1977 period and climate variability as the difference between 1978-1997 and 1958-1977 averaged fields.

## Slide 17

## Simple Indices of Climate Variability and Change(D. Karoly)

- There is very good agreement between the time variations of observed global-mean temperature and the ensemble-mean from the model simulations that included all forcings; increasing greenhouse gases and sulphate aerosols, as well as major volcanic eruptions and changes in total solar irradiance.  The modeled cooling after volcanic eruptions appears to be too large.

- CMEP Results