1 / 23

Colorado Center for Astrodynamics Research University of Colorado at Boulder

An assessment of IPCC 20th century climate simulations using the 15-year sea level record from altimetry Eric Leuliette, Steve Nerem, and Thomas Jakub University of Colorado, USA. Colorado Center for Astrodynamics Research University of Colorado at Boulder. Outline.

asa
Télécharger la présentation

Colorado Center for Astrodynamics Research University of Colorado at Boulder

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. An assessment of IPCC 20th century climate simulations using the 15-year sea level record from altimetry Eric Leuliette, Steve Nerem, and Thomas Jakub University of Colorado, USA Colorado Center for Astrodynamics Research University of Colorado at Boulder

  2. Outline • IPCC coupled climate models • 20th century climate experiment output compared to • sea level reconstructions • observed thermosteric sea level change • TOPEX/POSEIDON observations • Global mean sea level • Regional variations

  3. IPCC/CMIP • The Intergovernmental Panel on Climate Change Fourth Assessment Report (FAR) will be issued in 2007 • Coupled Model Intercomparison Project • 23 climate models from 16 institutions • Output variables include • Total sea level change • Steric sea level change

  4. 3rd Assessment Report 2001: 21st century predictions have little agreement

  5. Experiment Name Period Initial condition IPCC scenarios pre-industrial control > 100 years No anthropogenic or natural forcing present-day control > 100 years No natural forcing and anthropogenic influences will be set at present-day level. climate of the 20th century (20C3M) ~1850 - present pre-industrial control committed climate change present - 2100 end of the 20C3M run SRES A2 present - 2100 end of the 20C3M run 720 ppm stabilization (SRES A1B) present - 2300 end of the 20C3M run 550 ppm stabilization (SRES B1) present - 2300 end of the 20C3M run +1%/year CO2 (to doubling) ~70 yrs to 2x +150 present-day control or a pre-industrial control +1%/year CO2 (to quadrupling) ~140 yrs to 4x +150 pre-industrial control or a present-day control

  6. IPCC models reporting sea level time series IPCC models CGCM3.1 T47 Canadian Center for Climate Modelling and Analysis GISS AOM NASA/Goddard Institute GISS E20/Russell NASA/Goddard Institute INMCM 3.0 Institute for Numerical Mathematics, Russia MIROC 3.2 hires CCSR/NIES/FRCGC, Japan MRI CGCM2 3.2 Meteorological Research Institute, Japan

  7. Climate models • Climate models are designed to simulate long-term variability. • Coupled climate models are forced with natural and anthropogenic atmospheric conditions. • We should not expect the models to reproduce some observed interannual variability (i.e. ENSO).

  8. Reconstruction • Sea level Reconstruction • Method similar to Chambers et al. [2002] and Church et al. [2004] • Uses altimetry data decomposed into a number of empirical orthogonal functions (EOFs). • Employs a fit of spare tide gauge data to EOF spatial maps to reconstruct global variability. • Assumes that ~13 years of altimetry spans significant multi-decadal variability.

  9. Reconstruction (2) • Reconstructions two different methods • 1) EOFs produced directly from T/P and Jason altimetry (with seasonal signal removed) • 2) Detrended data + eustatic “EOF0” • Tide gauges selection criteria: Chambers et al. [2002] • Error analysis uses model output to estimate the impact of multi-decadal variability not spanned by the EOFs.

  10. Global mean sea level • GMSL 1930-2000

  11. GMSL TP-era • GMSL 1992-2004

  12. Reference Thermosteric sea level change(mm/year) Period Depth range (meters) Data Steric sea level Antonov et al. (2005) 0.40 ± 0.05 1955-1998 0-3000 Levitus et al. (2005b) Antonov et al. (2005) 0.34 ± 0.04 1955-2003 0-700 Levitus et al. (2005b) Ishii et al. (2005) 0.38 ± 0.04 1955-2003 0-700 Ishii et al. (2005) Antonov et al. (2005) 1.23 ± 0.2 1993-2003 0-700 Levitus et al. (2005b) Ishii et al. (2005) 1.8 ± 0.2 1993-2003 0-700 Ishii et al. (2005) Willis et al. (2005) 1.6 ± 0.3 1993-2003 0-750 Willis et al. (2005)

  13. Model GMSL (mm/yr) Thermosteric (mm/yr) ratio GMSL vs TSL CGCM3.1 –0.03 –0.09 3.00 GISS AOM 1.74 1.15 0.66 GISS E20/Russell 0.87 0.72 0.83 INMCM 3.0 1.28 1.25 0.98 MIROC 3.2 hires 1.04 0.98 0.94 MRI CGCM2 3.2 1.58 1.85 0.85 Observations 1.8 ± 0.3 20th century average trends (1900-2000)

  14. Thermosteric (1955-2000)

  15. Model GMSL (mm/yr) Thermosteric (mm/yr) ratio GMSL vs TSL CGCM3.1 0.74 0.56 0.76 GISS AOM 3.42 2.04 0.60 GISS E20/Russell 1.12 0.88 0.79 INMCM 3.0 1.25 1.33 1.06 MIROC 3.2 hires 1.16 1.19 1.03 MRI CGCM2 3.2 2.56 3.19 1.25 Observations 1.8 ± 0.3 0.40 ± 0.05 0.22 ± 0.05 late 20th century trends (1955-2000)

  16. Model GMSL (mm/yr) Thermosteric (mm/yr) ratio GMSL vs TSL CGCM3.1 0.32 0.79 0.40 GISS AOM 6.11 3.51 0.57 GISS E20/Russell 1.99 0.72 0.36 INMCM 3.0 1.34 1.38 1.03 MIROC 3.2 hires 2.71 2.32 0.85 MRI CGCM2 3.2 3.98 5.69 0.70 Observations 3.1 ± 0.5 1.5± 0.4 0.48±0.05 T/P-era average trends (1992-2000)

  17. Regional trends • TOPEX/Poseidon and Jason altimetry

  18. Regional trends • GISS AOM (1990-2000)

  19. Regional trends • NCAR CCSM 3.0 (1990-2000)

  20. Regional trends • UKMO HADCM3 (1990-2000)

  21. Regional trends • MIROC 3.2 (1990-2000)

  22. Regional trends • TOPEX/Poseidon and Jason altimetry

  23. Summary • IPCC FAR models generally underestimate the observed sea level change during the 20th century. T/P-era rates vary from 0.3-6.1 mm/yr. • The magnitude of steric sea level change and its contribution to total sea level change is overestimated over the 20th century. • Some high-resolution models appear to reproduce the magnitude and some of the geographical distribution of sea level change during the TOPEX/Poseidon-era.

More Related