klimaatsverandering oor suid-afrika van die volgende paar ...€¦ · klimaatsverandering oor...

Klimaatsverandering oor Suid-Afrika – van die volgende paar dekades tot die einde van die

eeu

Francois Engelbrecht1 and Christien Engelbrecht2

1. WNNR Natuurlike Hulpbronne en die Omgewing2. Landbou Navorsingsraad – Instituut vir Grond, Klimaat en Water

Summer-season rainfall

anomalies over the Free

State and North West

provinces (x-axis) and

Niño 3.4 sea-surface

temperature anomalies

(y-axis) for 1901-2015.

Rainfall anomalies from

CRU and GCPC are for

DJF. SST anomalies

from AMIPII are for

OND.

All anomalies were

calculated with respect

to the 1971-2000

baseline period.

CSIR-ACCESS

2015/16 1997/98

2016/17

2015: the warmest year on record!

The 2015/16 El Niño (image from NOAA): One of the strongest events ever recorded. Strong El Niño’s are projected to double in frequency towards the end of 21st century under low mitigation

In September 2016, the

entire summer rainfall

region was in a state of

mild drought, or worse.

The Free State, northern

KwaZulu-Natal and

eastern Mpumalanga

was in a state of severe

drought.

How will climate change

impact on the attributes

of drought in the mega-

dam region of SA?

Drought in southern Africa

A dust storm rolls over the plains of

the Free State in December 2015.

Drought in southern Africa

Depleted grazing in Kruger Park in

September 2016.

By September 2016,

The entire summer

rainfall region of

South Africa was in

a state of mild

drought, or worse.

The Free State,

northern KwaZulu-

Natal and eastern

Mpumalanga was in

a state of severe

drought .

2015 warmest year ever recorded globally (+ 1 ºC); summer of 2015/16

the warmest ever recorded over southern Africa (+ 2 ºC)

2015/16 anomalies relative to 2006/7 to 2014/15 climate; ARC station data;

Engelbrecht C et al. (2017) in preparation

© CSIR 2007 www.csir.co.za

Observed trends in annual-average temperatures over Africa 1961-2010

(Engelbrect et al., 2015; ERL 10: 085004)

Garland et al., 2015; Int J of Env Res and Public Health


The first African-based earth system model VRESM is

under development through a CSIR-

CSIRO collaboration

Global climate modelling at the CSIR NRE

• NWP and RCM capacity build around the conformal-cubic atmospheric model (CCAM) of the CSIRO

• A cube-based global model; semi-Lagrangian semi-implicit solution of the primitive equations

• Includes a wide range of physical parameterizations• Developed by the CSIRO Marine and Atmospheric Research

(McGregor, 2005) • Runs in quasi-uniform or in stretched grid mode• Multi-scale climate modelling.


Regional climate modelling over Africa using CCAM

CCAM applied in stretched-grid mode

Modest stretching provides a resolution of about 8 km over southern Africa

Development of Africa’s first coupled climate model is in progress

Development targets the main unresolved climate change questions for Africa and the SH in support of climate services

A C192 stretched-grid with resolution about 8 km over southern Africa

• Computer clusters available to the project include the CHPC in South Africa (24 000 + CPUs – VRESM allocation is currently ~ 3 000 000 core hours per quarter);

• The VRESM design has achieved some comparable resolution and computing times with less than 10% of the cores required by some more traditional coupling approaches.

• CSIR NRE data servers and CHPC VRESM allocated space currently amounts to 600 TB

HPC and code-

scalability

CCAM-TOM (CSIRO) scaling with 35atmosphere levels and 30 oceanlevels, suggesting excellentsimulation speed for computingresources

0.1

1

10

100

100 1000 10000

Sim

ula

tio

n y

ear

s p

er

day

Number of cores

CCAM scaling 35L 30OC192 (50 km) C384 (26 km) C768 (13 km)

From CSIRO: Martin Dix

Projected temp anomalies for 2081-2100 relative to pre-industrialconditions (0-degree world)

AR5 WG1 estimations relative to1986-2005 were adjusted with a 0.6°C factor

Only RCP 2.6 can safely keep us wellbelow the Cancun agreed 2 °C (LongTerm Global Goal), whilst the world iscurrently between A2 and RCP 8.5

Emission Scenarios and Representative Concentration Pathways

Scenario Temp anomalies relative to pre-industrial (adapted from AR5)

RCP 2.6 0.9 to 2.3

RCP 4.5 1.7 to 3.2

RCP 6 2.0 to 3.7

RCP 8.5 3.2 to 5.4

2.6


CSIRO-CSIR collaboration: 0.5°resolution global climate change downscalings for CORDEX using CCAM

Downscaling various CMIP5/AR5 CGCMs for different RCPs

Martin Dix, CSIRO


More uncertainty surrounds the projected rainfall futures of Africa under climate change

Southern Africa is projected to become generally drier by most models, whilst East Africa is projected to become generally wetter – an El Niño signal!

Figure: Projected changes in rainfall (mm) (left) and the average value of the Keetch-Byram drought index (right) over Africa for 2071-2100 relative to 1961-1990

Engelbrecht et al., 2015; ERL 10: 085004

Projections of changing annual average temperature (degrees C) over southern Africa for the period 2046-2065 relative to 1961-1990

CSIR-CHPC

Projections of changing annual average temperature (degrees C) over southern Africa for the period 2070-2099 relative to 1961-1990

CSIR-CHPC

Projections of changing annual rainfall over southern Africa for the period 2046-2065 relative to 1961-1990

CSIR-CHPC

Projections of changing annual rainfall over southern Africa for the period 2070-2099 relative to 1961-1990

CSIR-CHPC

Climate Change and the seasonal cycle

• Regional climate models realistically represent the present-day seasonal cycle in rainfall and circulation across the African continent (Engelbrecht et al., 2009)

• Model projections of future climate change are generally not indicative of significant changes in the seasonal cycle of rainfall and temperature over Africa, however, significant changes are projected in the amplitude of seasonal extrema

• The most interesting changes are to be found on the application side, e.g. a changing seasonal cycle in energy demand and wild fires (e.g. Engelbrecht et al., 2015; ERL 10: 085004)

• Figure shows the present-day (black) and end-of-the-century range of projected changes in the seasonal cycle of the Keetch-Byrandrought index over southern and tropical Africa (Engelbrecht et al., 2015; ERL 10: 085004)


Projected climate change futures for southern Africa: an “El Niño” signal?

The Free State and North West province are projected to drift into a temperature climate regime never observed in recorded history

Temperature increases of 5-9 degrees C are plausible by the 2081-2100 period

Significant rainfall reductions are projected

3 º

C w

orld

1.5

ºC

wo

rld


Main messages related to the climate-change signal

A robust pattern of drastic temperature rise is projected for southern Africa under the RCP8.5 and A2 scenarios – an actionable climate change signal.

Temperature increases are projected to range between 4 and 7 °C over the interior by the end of the century – increases larger than 6 °C are plausible over much of semi-arid southern Africa under low mitigation.

Temperature increases may plausibly reach 3-4 °C by the 2040s

Drastic increases in the number of high fire-danger days, very hot days and heat-wave days are projected to across the African continent under low mitigation.

The southern African region is likely to become generally drier. Over northeastern South Africa, Mozambique and Zimbabwe an increase in extreme rainfall events is plausible.

Multi-year El Niño type droughts may plausibly occur

from the mid-century (2036-2065 (onwards)

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