Clouds 101 Transcript

Clouds 101 Transcript

Narration: Kathleen Gaeta

Transcript:

00:00:01,890 --> 00:00:06,870

Clouds. They seem so simple.

When they appear darker we pack

00:00:06,870 --> 00:00:10,260

an umbrella. When they're

nowhere in sight, we pack extra

00:00:10,260 --> 00:00:15,180

sunscreen. Either way, we look

to clouds for more information

00:00:15,210 --> 00:00:18,960

than you might realize. But for

all that they can tell us they

00:00:18,960 --> 00:00:22,440

actually remain quite

mysterious, especially when it

00:00:22,440 --> 00:00:27,030

comes to how they impact the

climate. The question is because

00:00:27,030 --> 00:00:30,300

clouds are produced by the

climate, how will it change in

00:00:30,300 --> 00:00:34,230

climate impact clouds? And

conversely, clouds have an

00:00:34,230 --> 00:00:38,100

impact on our climate. So how

will a change in clouds affect a

00:00:38,100 --> 00:00:38,940

change in climate?

00:00:39,800 --> 00:00:46,460

Welcome to Clouds 101. Like all

good mysteries, this one begins

00:00:46,460 --> 00:00:50,330

with a sophisticated scientific

concept, Earth's radiation

00:00:50,330 --> 00:00:54,830

budget. Earth's radiation budget

describes the delicate balance

00:00:54,830 --> 00:00:58,160

between the sun's radiant energy

that reaches Earth, and the

00:00:58,160 --> 00:01:01,940

radiant energy that flows from

Earth back out to space. About

00:01:01,970 --> 00:01:05,990

30% of the sun's incoming

energy, essentially, the light

00:01:05,990 --> 00:01:09,410

and heat we're familiar with is

reflected back to space by

00:01:09,410 --> 00:01:12,200

gaseous molecules in the

atmosphere, tiny particles

00:01:12,200 --> 00:01:17,480

called aerosols, land, snow and

ice surfaces, and by clouds. The

00:01:17,480 --> 00:01:21,860

remaining energy from the sun,

roughly 70%, is absorbed by the

00:01:21,860 --> 00:01:25,970

planet. Most of this absorbed

energy heats up Earth's surface,

00:01:25,970 --> 00:01:29,360

while the rest is absorbed in

the atmosphere by gas molecules,

00:01:29,360 --> 00:01:34,280

clouds, and aerosols. So heat

can be both absorbed and

00:01:34,280 --> 00:01:39,020

reflected by clouds. We'll come

back to this later. Heat is also

00:01:39,020 --> 00:01:42,950

separately emitted by earth into

space in the form of thermal

00:01:42,950 --> 00:01:46,970

infrared radiation, which is the

kind of heat humans can only see

00:01:46,970 --> 00:01:50,600

through night vision goggles.

For Earth's temperature to

00:01:50,600 --> 00:01:54,710

remain constant, the absorbed

solar radiation and outgoing

00:01:54,710 --> 00:01:58,760

thermal infrared radiation must

balance one another. If the

00:01:58,760 --> 00:02:01,850

Earth's system is changed,

either through natural phenomena

00:02:01,850 --> 00:02:05,570

like volcanic activity, or

through unnatural phenomena like

00:02:05,570 --> 00:02:09,680

humans burning fossil fuels, an

imbalance in Earth's radiation

00:02:09,680 --> 00:02:13,190

budget occurs, and as a result,

the earth's temperature

00:02:13,220 --> 00:02:16,730

eventually increases or

decreases to restore an energy

00:02:16,730 --> 00:02:20,930

balance. In recent decades,

satellite and surface

00:02:20,930 --> 00:02:24,410

measurements clearly show an

energy imbalance taking place

00:02:24,410 --> 00:02:29,330

that's been increasing. Over the

past 150 years. The large rise

00:02:29,330 --> 00:02:32,120

in carbon dioxide emissions,

which accumulate in the

00:02:32,120 --> 00:02:35,960

atmosphere, has created an

enhanced greenhouse effect. This

00:02:35,960 --> 00:02:39,770

means that energy from the sun

still easily reaches Earth, but

00:02:39,800 --> 00:02:42,710

Earth's thermal infrared

radiation has a harder time

00:02:42,710 --> 00:02:47,150

getting out into space. This has

caused a decrease in how much

00:02:47,150 --> 00:02:51,320

heat Earth sheds. Consequently,

we have observed a rise in

00:02:51,320 --> 00:02:54,230

Earth's global mean surface

temperature, an increased

00:02:54,230 --> 00:02:58,580

melting of snow and sea ice, sea

level rise, and more extreme

00:02:58,580 --> 00:03:01,910

weather events. So that brings

us back to the mystery of

00:03:01,910 --> 00:03:06,110

clouds' long term effects on

climate. Here's what we know so

00:03:06,110 --> 00:03:10,790

far. Clouds impact the radiation

budget in two ways: by

00:03:10,790 --> 00:03:14,270

reflecting solar radiation back

to space, which leads to a

00:03:14,270 --> 00:03:18,620

cooling effect on the climate,

and by absorbing heat emitted

00:03:18,620 --> 00:03:21,800

from below the clouds that would

have otherwise escaped to space

00:03:21,800 --> 00:03:24,950

if the clouds weren't present,

leading to a warming effect.

00:03:25,910 --> 00:03:29,360

Which of these effects dominates

in any given location depends

00:03:29,360 --> 00:03:33,020

upon the cloud type. High

altitude clouds are typically

00:03:33,020 --> 00:03:36,890

thinner and colder than low

clouds, allowing for more solar

00:03:36,890 --> 00:03:40,340

radiation to pass through them

and reach Earth's surface. And

00:03:40,340 --> 00:03:43,520

because they're cooler, they

emit less thermal infrared

00:03:43,520 --> 00:03:46,760

radiation to space, so they have

a net warming effect on the

00:03:46,760 --> 00:03:50,060

climate. Clouds at low

altitudes, on the other hand,

00:03:50,090 --> 00:03:53,570

are generally thicker and

reflect more solar radiation

00:03:53,570 --> 00:03:58,040

back out to space. They're also

typically warmer, so they emit

00:03:58,040 --> 00:04:01,490

more thermal infrared radiation

and therefore have a net cooling

00:04:01,490 --> 00:04:05,420

effect on the climate. We also

know that when the climate

00:04:05,420 --> 00:04:09,200

warms, Earth can respond in ways

that leads to further warming.

00:04:09,620 --> 00:04:13,310

For example, as temperatures

increase, we see snowpack and

00:04:13,310 --> 00:04:16,880

sea ice melting away in polar

regions, a loss of white

00:04:16,880 --> 00:04:20,840

surfaces that reflect the solar

radiation. That means darker

00:04:20,840 --> 00:04:24,140

colored land and oceans left

behind absorb more solar

00:04:24,140 --> 00:04:27,800

radiation, and so more heat is

added to the climate system.

00:04:28,400 --> 00:04:32,450

This cycle of more heat, more

melt and more absorption of

00:04:32,450 --> 00:04:36,410

solar radiation is called a

feedback cycle. And it doesn't

00:04:36,410 --> 00:04:41,960

end there. A feedback cycle also

happens with clouds. Climate

00:04:41,960 --> 00:04:45,620

models predict a decrease in low

altitude cloud coverage over the

00:04:45,620 --> 00:04:49,340

globe as the climate warms,

since low clouds are the highly

00:04:49,340 --> 00:04:53,330

reflective type, a decrease in

low cloud coverage means more

00:04:53,330 --> 00:04:56,000

heat will be added to the

Earth's system, leading to

00:04:56,000 --> 00:04:59,870

further warming. And clouds

impact the climate in another

00:04:59,870 --> 00:05:04,430

way too: Through the water cycle

producing rain and snowfall.

00:05:05,120 --> 00:05:08,180

Water at Earth's surface

evaporates, providing the

00:05:08,180 --> 00:05:11,690

atmosphere with a supply of

water vapor. Depending on the

00:05:11,690 --> 00:05:15,440

air temperature and atmospheric

pressure, the air can only hold

00:05:15,440 --> 00:05:19,790

so much water vapor until it

becomes saturated. When that air

00:05:19,790 --> 00:05:23,330

saturated with water vapor

cools, the water vapor turns

00:05:23,330 --> 00:05:26,360

back into liquid water droplets

and forms clouds.

00:05:27,930 --> 00:05:31,436

When these droplets or ice

crystals accumulate, that is

00:05:31,500 --> 00:05:35,453

what we call a cloud. When the

droplets or ice crystals within

00:05:35,516 --> 00:05:39,214

the cloud grow to be large

enough, they eventually fall to

00:05:39,278 --> 00:05:42,912

the ground or ocean as rain,

snow or hail. This brings us

00:05:42,976 --> 00:05:46,801

back to the mystery at hand.

Because clouds both reflect and

00:05:46,865 --> 00:05:50,244

absorb energy from the sun

impacting both ends of the

00:05:50,308 --> 00:05:54,197

radiation balance and play a

massive role in the water cycle,

00:05:54,261 --> 00:05:57,576

any changes in clouds will

result in a change in our

00:05:57,640 --> 00:06:01,465

climate. But clouds are also

produced by our climate, so any

00:06:01,529 --> 00:06:05,290

change in climate will result in

a change in clouds. As you

00:06:05,354 --> 00:06:08,924

probably now realize the

relationship between clouds and

00:06:08,988 --> 00:06:12,240

the climate is incredibly

complex, and NASA is on a

00:06:12,303 --> 00:06:16,320

mission to understand it. Using

NASA's Earth Observing fleet of

00:06:16,384 --> 00:06:19,827

satellites like Calipso and

instruments like Ceres and

00:06:19,890 --> 00:06:23,652

MODIS, scientists have been

collecting vital data on clouds

100

00:06:23,716 --> 00:06:27,669

to be able to precisely model

their behavior. A key ingredient

101

00:06:27,732 --> 00:06:31,621

to unraveling the mystery of

clouds lies in the collection of

102

00:06:31,685 --> 00:06:35,447

global accurate multi decadal

climate data records of cloud

103

00:06:35,511 --> 00:06:39,272

properties and their influence

on Earth's radiation budget.

104

00:06:39,336 --> 00:06:43,480

Once we can accurately and fully

understand the physics of clouds

105

00:06:43,544 --> 00:06:47,624

through observations, that data

can then be used to help improve

106

00:06:47,688 --> 00:06:51,960

climate and weather models so we

can better prepare for the future.