Climate predictions and projections Prof. Dr. ir. Wilco Hazeleger

1989-1994 Wageningen Universiteit/University of Reading

Bodem, Water en Atmosfeer – specialisatie meteorologie

1994-1998 KNMI/Universiteit Utrecht

Promotie fysische oceanografie

1999-2001 Columbia University (New York)

Postdoc Climate variability research

2002-2006 KNMI

Scientific Researcher

2006 – KNMI

Head of Division

2010 – Wageningen University

Hoogleraar Klimaatdynamica

Skill simplest weather and climate prediction

Autocorrelation at ‘lag n’ of averaged temperature at 2 meters (Hazeleger 2012; Thanks to G.J. van Oldenborgh)

Weather and climate models

upguut

2

Supercomputers

BULL KNMI, 58 Tflop (58 1012 operations/s, highest world wide 20 1015 = 20 Pflop)

IPAD-2 160 MFlop (160 106 operations/s)

Climate model Weather model ~ 150 km ~ 20 km

Grid climate and weather models

Natural variability

Chaos

Global averaged surface temperature wrt 1950-1980

Sterl et al., Geophys. Res. Lett., 35, 2008.

Ensemble with 1 model ‘samples’ natural variability

External drivers

Observations Modellen with all natural forcings (sun, volcanoes) Models with natural and anthropogenic forcings

IPCC, Figuur SPM 6

Weather predictions (now – 15 days)

Ensemble prediction

Weather forecast

How good are weather predictions?

Seasonal predictions (1 – 12 months)

How good are seasonal predictions?

Correlation between observed temperature and predicted temperature

(2-4 months in advance; using 1981-2010 forecasts)

Decadal predictions

Climate in the next decade ( - 2021)

Skill in temperature good, but comparable to a statistical model

2016-2020 wrt 1971-2000

Smith et al 2012

Climate projections (- 2100)

Changes in boundary conditions: greenhouse gases

Figure SPM.7

Global annual mean temperature change (wrt 1986 – 2005)

2.5 to 4.8°C

0.3 to 1.7°C

Long term temperature projections

Temperature and precipitation projections

RCP 8.5, change wrt 1986 -2005

Precipitation projections for Europe

summer winter

RCP 8.5, change in 2081-2100 wrt 1986 -2005 Hatching: 66% of all models; double hatching: 90%

IPCC Figuur 14.29

Can we predict weather and climate?

•Autocorrelation of observed 2-meter temperature, N-averaged, at lag N; lines) •Correlation skill from dynamical forecasts (ECMWF EPS, monthly forecasts, DEMETER and ENSEMBLES multimodel seasonal to decadal forecasts; symbols)

Hazeleger et al in prep

Predictability of weather and climate

‘Chaotic’ weather is predictable up to ~15 days

Statistics of weather is in some regions and some seasons

predictable months ahead

Predictable ‘slow’ components in the climate state: ocean, ice,

soil, atmospheric composition predictability decades ahead

External forcing of Earth system: greenhouse gases, land use,

solar radiation, volcanic ash unpredictable

Systematic error of models

‘what if’ climate scenarios: physical plausible and consistent

pictures of a future climate