1
00:00:00,000 --> 00:00:03,330
It’s not easy to see aerosols in Earth’s atmosphere, 

2
00:00:03,350 --> 00:00:04,370
but they’re there.

3
00:00:04,390 --> 00:00:07,470
And NASA scientists say these tiny particles 

4
00:00:07,490 --> 00:00:08,870
are having a profound effect 

5
00:00:08,890 --> 00:00:12,200
on snowpack and spring climate in the Northern Hemisphere.

6
00:00:12,220 --> 00:00:16,100
At any moment, millions of tons of aerosols lifted by winds 

7
00:00:16,120 --> 00:00:19,580
and generated by wildfires and the burning of fossil fuels

8
00:00:19,600 --> 00:00:21,580
are traveling across the globe. 

9
00:00:21,600 --> 00:00:23,240
In snow-covered regions,

10
00:00:23,260 --> 00:00:26,500
certain kinds of aerosols can darken the snow and ice 

11
00:00:26,520 --> 00:00:30,630
causing it to absorb more of the sun’s energy and melt faster.

12
00:00:30,650 --> 00:00:33,890
Scientists call this phenomenon the snow darkening effect.

13
00:00:33,910 --> 00:00:37,600
The snow darkening effect is basically another way of saying 

14
00:00:37,620 --> 00:00:40,130
what happens when snow gets “dirty.”

15
00:00:40,150 --> 00:00:42,730
Snow that has become darkened by aerosols

16
00:00:42,750 --> 00:00:46,140
absorbs more sunlight, than snow that is pristine. 

17
00:00:46,160 --> 00:00:47,880
This may not seem significant,

18
00:00:47,900 --> 00:00:50,470
but it can actually have a big effect 

19
00:00:50,490 --> 00:00:52,670
on the melting during spring.

20
00:00:52,690 --> 00:00:54,730
Using a NASA climate model,

21
00:00:54,750 --> 00:00:58,310
researchers studied the impact of three types of aerosols 

22
00:00:58,330 --> 00:01:01,310
on snowpack in the Northern Hemisphere spring,

23
00:01:01,330 --> 00:01:04,670
specifically dust, black carbon, and organic carbon.

24
00:01:04,690 --> 00:01:07,380
The areas colored red to purple on this map 

25
00:01:07,400 --> 00:01:10,640
show where the surface absorbed more energy from the sun 

26
00:01:10,660 --> 00:01:14,170
due to snow that has become darkened by these aerosols.

27
00:01:14,190 --> 00:01:16,270
This surface warming resulted in 

28
00:01:16,290 --> 00:01:18,360
reduced amounts of snow in spring, 

29
00:01:18,380 --> 00:01:20,780
shown here in areas colored blue.

30
00:01:20,800 --> 00:01:25,270
These reductions might reflect an earlier melting of winter snowpack 

31
00:01:25,290 --> 00:01:28,840
and ground warming of areas normally covered by snow.

32
00:01:28,860 --> 00:01:30,150
In some places, 

33
00:01:30,170 --> 00:01:33,260
temperatures are up to about 10 degrees Fahrenheit warmer 

34
00:01:33,280 --> 00:01:35,950
than it would be if the snow were pristine.

35
00:01:35,970 --> 00:01:39,320
As we add more of these aerosols to the mix, 

36
00:01:39,340 --> 00:01:43,850
we are changing the makeup of particles in the air and snow, 

37
00:01:43,870 --> 00:01:48,390
potentially increasing our overall impact on Earth’s climate. 

38
00:01:48,410 --> 00:01:50,757