Using climate change to predict Nile flow

Suzanne Young

March 8, 2004

1.096

The Greenhouse Effect

• 1985 a French-Soviet drilling team at Vostok Station in central Antarctica

• ice core two kilometers long that carried a 150,000-year record, a complete ice age cycle of warmth, cold and warmth

• the level of atmospheric CO2 had gone up and down in remarkably close step with temperature

http://www.aip.org/history/climate/co2.htm#L_0242

http://www.aip.org/history/climate/co2.htm#L_0242

CO2 is rising!

So what?

• Historical records of Nile floods reveals strong correlation between low Nile floods and cold summers in Europe, and conversely, high Nile floods and warms summers in Europe.

• Warmer temps → increased ET → higher precipitation → higher Nile floods

• Climate change influences the height of Nile floods.

A Consistent PatternFluctuations in Nile flood levels coincide with climatic changes in the Sahel and even the flow of the Senegal River at the other end of Africa. (Hassan 1998)

http://content.kluweronline.com/article/147859/fulltext.pdf

Nile River Basin

Average Longterm Monthly Nile flows, 1872-1986

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25

January February March April May June July August September October November December

Dis

char

ge (

km^3

/mon

th)

Nile discharge, 1872-1986

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1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980

An

nu

al d

isch

arg

e (k

m^3

/yea

r)

Longterm annual average = 88.1 km^3/year

What are General Circulation Models (GCMs)?

• Mathematical representations (i.e. computer simulations) of atmospheric and oceanic properties and processes that attempt to describe earth's climate system.

• Developed in 1960s, has become chief tool in analyzing effects of climate change.

• Many variations!!!

Climate Change Scenarios for Nile Basin (Yates 1998b)

• UKMO (United Kingdom Meteorological Office): warmest & wettest, temp. increase as high as 4°C and precipitation increases 26-25%.

• GISS (Goddard Institute for Space Studies, New York, NY): also significant increases in precipitation over most of Nile basin with warming similar to UKMO.

• GFDL (Geophysical Fluid Dynamics Laboratory steady-state, Princeton, NJ): gave larger increases in temp. and smaller increases in precipitation in the northern regions of the basin.

• GFDLT (Geophysical Fluid Dynamics Laboratory transient, Princeton, NJ): similar to GFDL but with larger decreases in precipitation and slightly higher warming.

• MPI (Max Plank Institute, Hamburg, Germany): coolest scenario and gave moderate increases in precipitation over the Lake region and Atbara and large increases over the Sudd swamp region and Blue Nile basins.

• CCC (Canadian Center for Climate, Victoria, Canada): gave precipitation decreases in all the basins except the Atbara--precipitation increase between 150 and 200% occurred during the peak precipitation months (July-September).

Range of discharges for major points along the Nile (Summary of Yates 1998b results)

Two numbers on ends of each line represent extreme discharges of six GCM scenarios, whereas boxed number is historic average; Additional tick marks on each line are remaining GCM scenarios, which indicate range of climate change induced flows of Nile Basin.

Future Nile flow

• Extensive literature review, wide disparity• Most predict increase in flow• Johns 2003 most accurate?

– In next 100 years, temps increase ~5.3 K, precipitation increase by 1% per K

• Best fits to GFDL scenario (Yates 1998b)– 6% increase in Nile flow– Predicted long term annual average = 93.43

km3/year

Historical Nile discharge (1872-1986) vs. Predicted Nile discharge (next hundred years)

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1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980

Ave

rag

e d

isch

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m^3

/yea

r)

Predicted

Historical

Predicted longterm annual average = 93.43 km^3/year

Historical longterm annual average = 88.4 km^3/year