Climate of Our Future

ScienceDaily (Sep. 19, 2008) — The Lake Tanganyika area, in southeast Africa, is home to nearly 130 million people living in four countries that bound the lake, the second deepest on Earth. Scientists have known that the region experiences dramatic wet and dry spells, and that rainfall profoundly affects the area’s people, who depend on it for agriculture, drinking water and hydroelectric power.

Scientists thought they knew what caused those rains: a season-following belt of clouds along the equator known as the Intertropical Convergence Zone (ITCZ). Specifically, they believed the ITCZ and rainfall and temperature patterns in the Lake Tanganyika area marched more or less in lockstep. When the ITCZ moved north of the equator during the northern summer, the heat (and moisture) would follow, depriving southeast Africa of moisture and rainfall. When the ITCZ moved south of the equator during the northern winter, the moisture followed, and southeast Africa got rain.

Now a Brown-led research team has discovered the ITCZ may not be the key to southeast Africa’s climate after all. Examining data from core sediments taken from Lake Tanganyika covering the last 60,000 years, the researchers report in this week’s Science Express that the region’s climate instead appears to be linked with ocean and atmospheric patterns in the Northern Hemisphere. The finding underscores the interconnectedness of the Earth’s climate — how weather in one part of the planet can affect local conditions half a world away.

The discovery also could help scientists understand how tropical Africa will respond to global warming, said Jessica Tierney, a graduate student in Brown’s Geological Sciences Department and the paper’s lead author.

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