Taking the shine off: albedo and global temperatures
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Why is Earth’s albedo decreasing and how does it affect global temperatures?
The Economist. Hello and welcome to The Intelligence from The Economist. I'm Jason Palmer.
And I'm Rosie Bloor.
Today on the show, West Africa becomes a global node in the cocaine trade and America's stubborn scarcity of female redwinners.
The Economist
First up, though,
The surface temperature of the oceans between 60 North and 60 South has been at a record for the time of year all through July and almost all through June. And so the seas of the world are very hot at the moment.
Oliver Morton is our Planetary Affairs editor.
The heat in the oceans is the biggest store of heat on the planet. And it's driven by how much heat the planet absorbs from the sun and how much it gives off as infrared radiation. And the Earth is absorbing considerably more heat than it used to be absorbing. Part of this is an effect of global warming. There were fewer clouds, scarcer ice caps, and that means that the Earth absorbs more energy. And then there's a second issue, which is that also the Earth is being made less reflective because we're putting less of particular sorts of pollutant into the atmosphere.
So the Earth is reflecting less energy back. Explain what role that really plays.
Yeah, that's right. If you were standing outside the Earth and looking at it, it would, just at the edges of human capacity to see, it would be getting just a little bit dimmer over the decades. And this leads to more sunlight being absorbed. And that means that there's more energy coming into the system. The amount of energy leaving the system is also going up, but not as quickly. And so you get basically a buildup of energy in the system.
Olly, we know about global warming. What's new here in what you're talking about?
There are two things going on here. One is you say we know about global warming and we know about it in general. But I think a thing that's not very thoroughly appreciated is that though the warming takes place in the atmosphere of the greenhouse gases to begin with, it then spreads throughout the system in various complicated ways. And one of the ways that it spreads through the system is
What is the Earth’s energy imbalance and how is it measured?
is diminishing the amount of cloud cover. And that adds to the warming further because light that's not reflected from the clouds gets absorbed and adds to the warming. So this is what we call a climate feedback. And it's sort of like climate change feeding on itself. And so the change just due to the greenhouse gases becomes a change due to greenhouse gases and this new effect of the Earth being less reflective. But there's also a second effect, which is distinct, which is that humans put little particles into the atmosphere all the time, and this is, by and large, rather bad for our health. The most important pollutant in this is sulfur. Over the past 20 years, the amount of sulfur in the atmosphere started to peak, and then it started quite quickly to decline.
And when sulfur levels decline, the level of little, what they call aerosol particles in the atmosphere also declines, and this means that the Earth again reflects away less sunlight, so absorbs more.
You're saying that less energy is reflected back.
Yes, I'm saying that less energy is being reflected back out into space when sunshine hits the Earth. And that means that in general, more energy is being absorbed. And the amount of energy absorbed by the Earth, what's called the Earth's energy imbalance, has more than doubled in the last 20 years.
And what impact does that actually have?
The impact is global warming. It's how global warming works, but it's a more sophisticated but also more fundamental way of seeing the same effect as you see in rising global temperatures.
And how do we measure how much impact it's having?
We measure the size of the imbalance. The size of the imbalance is mainly measured from satellites, and in particular by a set of instruments on NASA satellites. And that measurement is very, very complicated to make. It's really hard to calibrate satellite measurements. And although they do a brilliant job of it, I think the thing that really convinces people that those measurements are true is that we have a completely different set of measurements that back it up, which is
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Chapters
8 chapters
1
Why is Earth’s albedo decreasing and how does it affect global temperatures?
0:03–2:40
2
What is the Earth’s energy imbalance and how is it measured?
2:40–5:13
3
How do cloud‑cover feedbacks amplify warming?
5:13–8:12
4
What role does the decline in atmospheric sulphur aerosols play in warming?
8:12–11:29
5
Why is West Africa becoming a major hub for cocaine trafficking?
11:29–14:12
6
How do cartels use mother vessels and go‑fast boats to evade European law‑enforcement?
14:12–16:52
7
What does data show about American wives out‑earning their husbands and relationship strain?
16:52–19:41
8
What are the policy options for increasing Earth’s reflectivity and their controversies?
19:41–22:38