Down to Earth: Rare deluge to hit parts of the Sahara

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00:00Now one of the driest places on the planet is about to experience an exceptionally rare downpour.

00:07The Sahara Desert is expected to see record amounts of rain in the next two weeks,

00:12with some areas of the parched desert set to receive five times their average rainfall for

00:18August and for September. And that could trigger flooding elsewhere in North Africa.

00:24I'm joined on the set to hear more about this by our environment editor Valerie de Camp. And

00:29Valerie, first of all, this certainly sounds unusual. Tell us why this is happening.

00:34Well, it is a very rare weather phenomenon. The Sahara receives little to no rainfall at all

00:41every single year. And when it does rain, it's an average of three inches per year. And so

00:47when some parts of the region are expected to see five times that average, I mean,

00:52if you add that up, it sounds like it's not a lot. But in some parts, it could be a year's

00:57worth of rain in just a couple of days. So multiple rounds of showers and thunderstorms

01:03expected in places like Mali, Chad, Libya, Niger, Sudan and Morocco. And so I have this map here

01:11of the Sahara Desert is what you see in yellow. And so it is normally an area of permanent high

01:18pressure. And what that means that is that it prevents clouds from forming and so moisture

01:22building up. And that is what keeps the desert dry. And it sits right above this red line that

01:30you can see there. It's called the Intertropical Convergence Zone. And this area is actually very

01:36humid across this red line, very prone to heavy rain. And so usually areas characterized by

01:44very lush vegetation. And so what's happening now with this unusual weather pattern is that

01:50that zone, that red line is actually moving north. And as that moves north, it's actually

01:58bringing rain to areas where usually you don't see rain at all. So we know that that convergence

02:05zone is actually moving 152 miles further north into the Sahara. And air over North Africa is now

02:15holding three to four times more moisture than usual, causing rainfall. And might this cause

02:22problems, Valerie, far beyond the Sahara itself? Well, I mean, if you think rain over parched land,

02:28you know, that doesn't have to be a bad thing. Well, actually, it could bring pockets of flooding

02:35to places like Chad, Libya, Niger, and Algeria. And that is because sand dunes are not able to

02:40hold excess runoff. When the ground is really dry, it's almost like a hard surface. And so it can't

02:47absorb water. And that can, you know, lead to flash floods. And that's what you were seeing now

02:54is actually footage from Sudan. Several villages have been swept by floods in the last couple of

03:02days. 31 people have died. And you can see how the ground can't really hold that water. And it's

03:08pretty much what you get, for example, when you see climate-induced droughts. And really, the

03:15atmosphere building up, holding a lot of moisture, followed by heavy rain, you end up getting flash

03:22floods. And so that can, it's pretty much kind of the same phenomenon with desert rain. You know,

03:27the ground can't hold that water. And just finally, is climate change to blame here?

03:33I mean, when you have unusual weather patterns, it doesn't always have, you know, the fingerprints

03:38of climate change. You can have just unusual weather patterns. At this stage, nobody can tell

03:44if this is actually related back to climate change. The field of attribution science, which aims to

03:50link specific weather anomalies to climate change, is progressing. But you need a lot of data. You

03:57need time, and you need a lot of hindsight in order to make that claim that this is, you know,

04:02related specifically to climate change. But it is worth looking at this in the context of climate

04:09change, because it's easy to associate climate change with heatwave, higher temperatures in

04:14parts of the world where we're not used to having those high temperatures, and kind of disregarding

04:20other kinds of extreme weather, which can be, you know, rainfall in places like the Sahara.

04:27It doesn't necessarily cancel out the fact that we are having, you know, climate change and global

04:32warming. And what's also quite interesting to point out is, you know, this red line that I was

04:39talking to you about earlier, this convergence zone, the fact that it is moving north into the

04:45Sahara, also helps explain why we have had a mild hurricane season north of the Atlantic, in the

04:53Atlantic Ocean, because normally tropical storms form, you know, along this red line, and then they

05:01roll over towards the western Africa into the Atlantic Ocean, and that's how you end up having

05:07tropical cyclones in the Atlantic. And so the fact that there's something unusual happening here,

05:14hurricanes have gone quiet actually in the Atlantic, and so it's really important to see how

05:18interconnected all of these things are, and so when something is off in one part of the world,

05:25you know, chances are something is also off somewhere else, and why it's so important to

05:31kind of keep this as a balance, you know, when we talk about climate and weather phenomenons.

05:38All right, really interesting. Thanks very much, Valerie de Camp, our environment editor for us there.

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