To talk about war in Africa—in Sudan and Somalia, to name two countries now battling a horrendous drought—means talking about the weather.Last week, the United Nations declared that the drought striking much of Africa’s Horn, the knobby spit of land off the continent’s east coast, is the worst on record for the past 60 years. The seasonal rains have failed for at least the third year in a row, and there’s no chance that things will get better until at least 2012.

At least 17 million people are facing famine; one out of four children is currently battling starvation. It’s tough to say, but it’s true that this never-ending litany of African catastrophes makes it difficult for us to pay attention.

So, beyond the faces of starving children, beyond statistics so mind-boggling they leave most of us feeling overwhelmed and defeated, let’s consider the science that binds drought to conflict.

It’s no accident these battlegrounds lie where they do: both Sudan and Somalia lie within a zone of extreme weather—where the dry air of the northern hemisphere collides with the wetter air of the south.

This zone, which moves north or south of the equator, depending on the season, is called the inter-tropical convergence zone—some scientists call the ITCZ, the “itch” for short. Inside the itch, extreme weather—both flooding and drought—seem to be intensifying. Most scientists believe this is one effect of climate change.

No question, weather is one cause of war. As the earth grows warmer, and rains are no longer dependable, farmers no longer know when to plant their crops. Centuries-old cycles are changing, and no one knows how to predict them. As a result, crops fail and that causes famine.

This worsening weather affects herders, too. People who keep cows depend on stable cycles of rain and drought to feed and water their cattle. When the rains fail in the north, they have to push farther south into wetter land that’s already settled by farmers. Here’s one way that religion comes into this cycle: The northern herders, who are nomads, are frequently Muslims, thanks to centuries of travel along trading routes. Across much of inland Africa, as they move south, they run into farmers who are largely Christians or follow traditional religions.

Bam! A collision over land—really over grass for food and drinking water—becomes a collision over religion and identity.

We see this now in Sudan. One little known fact about Sudan, is that it’s not just changing weather that has push nomads farther south. In the north, President Bashir’s government has leased out large plots of land so that nomads can’t travel over their old routes. (Until some years ago, the late Osama bin Laden was one of these large landholders.)

Right now, in Sudan, there’s a chance that things could change. This week, Southern Sudan, New Sudan, declares its independence and becomes the world’s newest country. This is great news, but it comes at a price.

Northern forces are currently waging an all too familiar bombing campaign in the Nuba Mountains—against Nuba’s Muslims and Christians alike. President Bashir, who, like Ahmed Haroun, the local governor there, has been indicted for crimes against humanity by the International Criminal Court, has launched a scorched earth campaign against the Nuba people in order to wipe any resistance to his rule off the face of the earth.

Here are the same patterns of two kinds of identities smashing up against each other, thanks to centuries of migration driven by geography and weather.

Africa’s extreme weather patterns affect America, too. Those storms kicked up in the collision zone around the equator spin westward off the coast of Cape Verde. They spin over the Atlantic Ocean, where the worst of them gather speed.

These African storms become our East Coast hurricanes. The same weather patterns that bind parts of Africa to drought and conflict drive our worsening weather as well.

Come August, when these storms start to strike the United States, Africa’s wars will hit closer to home.