Why are we here?

Key Impacts of climate change in the coastal zone

• Sea-level rise – inundation – storm surges, waves – coastal erosion – Impacts on emergency and escape routes– Break down in law and order– Environmental refugees – a here and now

issue• not “if” but “when and where and how will

we respond?”

People to respond

-Tens of millions(far fewer with optimum protection)

Can measure sea-level rise in other units!

Wide range of projections

Church et al., 2001

Despite all of the uncertainties we do know quite a lot.

Reconstructed sea level for 1870 to 2000 indicates an acceleration of the rate of sea-level

rise

Church and White, 2006

Estimates of thermosteric sea level rise from 1993 – 2003 using a variety of analysis techniques (Willis et al., 2004, Lombard et al., 2005, Domingues et al., 2006) are similar, about 1.6 mm/yr (about 1.3 mm/yr for OI estimates), but with interannual differences. All of these are strongly dependent on XBT data.

Does the 1998 ENSO signal seen in sea level have a thermosteric component?

Domingues et al., 2006

Willis et al., 2004, Lyman et al. 2006

Lombard et al., 2005

5 estimates of upper ocean thermosteric sea level rise, 1993 - 2003

Calculations with a common dataset are needed to reconcile these differences.

Glaciers contribution to sea levelGlaciers contribution to sea level

From Position Paper ‘Cryospheric Contributions’

0.8 +/- 0.4 mm/yr

Contribution of Ice sheets to Sea LevelContribution of Ice sheets to Sea Level

From Position Paper ‘Cryospheric Contributions’

Zwally et al. (2005)Krabill et al. (2004)Thomas et al. (2006)Vellicogna and Wahr (2005)Ramillien et al. (2006)Rignot & Kanagaratnam (2006)

1. Greenland1. Greenland

2. Antarctica : « probable net loss but close to balance » 2. Antarctica : « probable net loss but close to balance »

0.3 +/- 0.15 mm/yr

A major improvement – decreased uncertainty by a factor of 3+!

Antarctic current ice evolution from glaciological modeling

-> Antarctic ice sheet at the tail end of the last glacial-interglacial transition: still responding to WAIS grounding line retreat since LGM, but close to minimum with only small remaining trend

Huybrechts, QSR, 2002

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

01234567

time (ka BP)

Sea level (m)

before present

Coral data

Serpulid data

Archaeological

Tide gauge

Paleo data opportunitiesExtending historical data over centuries to milleniaConstraining Ice Sheet contributions

Increasing concern about ice-sheet stability and a substantially larger rise in sea level

•Surface melting

•Dynamic instability

Effect of global land water storage on global mean sea level

agreement between ORCHIDEE and LaD.(Land Dynamics LSM of GFDL)

greatest variation is associated with ground water, followed by soil moistureno significant

trend was detected strong decadal

variability driven by precipitation, strong decrease in the beginning of 1970s

Milly, P. C., D., A. Cazenave, and M. C. Gennero (Proc. Natl Acad. Sci, 2003)

Ngo-duc T., K. Laval, J. Polcher, A. Lombard and A. Cazenave (GRL, 2005)

Threats: ITRF on “shaky ground”:current collocations

– Links between SLR-VLBI-GNSS are weakening in time

– Uneven station distribution leads to biases

– No long-term systematic commitment to support ITRF

(2)(16)(59)(8)

We now have an ITRF – need to support it through GGOS and GEOSS

Viscous “Memory” of Solid Earth to Past Ice-Ocean Mass Flux

Emanuel’s Multi-basin Tropical Cyclone Power Dissipation Index (PDI) has increased substantially over past 50 years, along with tropical SSTs

Source: Kerry Emanuel, MIT, http://wind.mit.edu/~emanuel/anthro2.htm. SST anomaly (deg C) with arbitrary vertical offset. PDI scaled by constant.

0

5

10

15

20

25

30

35

40

45

NorthAtlantic

East Pacifc WestPacific

SouthwestPacific

NorthIndian

SouthIndian

1975-1989

1990-2004

Webster et al.: The percentage of hurricanes which reach Category 4-5 has increased in all basins, comparing two recent 15-year periods…

Question: Are the historical data adequate for this conclusion?

Source: Adapted from Webster et al., Science, Sept. 2005.

Integration

First Example: Small Number of Tide Gauges

Mitrovica et al., 2001Tamisiea et al., 2001

We can make progress in closing the budget!

We can make progress in closing the budget!

We can make progress in closing the budget!

We can make progress in closing the budget!

Integration – Next steps?

Need to present probabilities – risk based framework

Simulated vs. observed thermosteric sea level rise

J. Church (pers. comm. 2006)