What is Climate Change? Crash Course Geography #14 - Free Educational videos for Students in K-12

What is Climate Change? Crash Course Geography #14 - By CrashCourse

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00:0-1	In 2018 , I got to walk across the surface
00:02	of a receding glacier in Iceland , from where I
00:04	stood I could see a patch of snow and ice
00:06	off in the distance , the last remnants of another
00:08	glacier that had since melted away . That ice speckled
00:11	area was all that remained of 800 year old Nokia
00:14	coke or coke glacier , which was officially declared dead
00:17	in 2000 and 14 by Icelandic geologist odor Sigurdsson .
00:21	It once banned an area as large as 38 square
00:23	kilometres in 2000 and 19 . The loss of Okay
00:26	Uncle was commemorated with a plaque on the site of
00:28	the former glacier . It's the first monument dedicated to
00:31	a glacier lost to human induced global warming , looking
00:34	after our planet and all its dynamic ecosystems and landscapes
00:38	, including glaciers is everyone's job . We know rising
00:41	temperatures are correlated with rising carbon dioxide in the atmosphere
00:44	and the amount of carbon dioxide generated by our day
00:47	to day actions can have an effect on the other
00:49	side of the world . But while individual actions matter
00:51	who is emitting carbon dioxide is highly unequal , about
00:55	half of total US . emissions in 2019 were direct
00:58	emissions from corporations coming from sources like power plants and
01:01	oil and gas production facilities . So they also have
01:04	responsibility to share the burden knowing who or what is
01:07	emitting . Carbon dioxide is only part of understanding climate
01:10	change . We also study who emissions effect and the
01:12	geographical impacts of a warming planet . Climates are complex
01:16	, so I don't have all the answers . But
01:18	there's a lot we can learn . I'm Elise a
01:20	career and this is crash course . Geography . Even
01:30	with the problem is complicated as climate change . We
01:32	can start with a picture like this picture of Muir
01:35	glacier in Alaska from 2004 pictures and maps can show
01:38	us where landmasses , oceans and geographical features are located
01:42	, which is spatial information that we kind of take
01:44	for granted the earth is dynamic and we have to
01:47	remember that both pictures and maps are really snapshots of
01:49	a particular time . So if we compared this image
01:52	to past ones of the same area , we'd see
01:54	how it's changed and we could explore why changes happening
01:56	here . A photo taken in 1941 from the exact
01:59	same spot as the recent photo shows an entirely different
02:02	landscape . The glacier was much bigger after looking at
02:05	lots of old and new photographs , current glacial ,
02:08	logical surveys and the geologic record . We know glaciers
02:11	around the world . In places like Alaska , the
02:13	Swiss , ALps and Mount Kilimanjaro have shrunk dramatically muir
02:16	glacier is just one example to get deeper into the
02:19	why we know that ice and snow melt faster as
02:21	air temperatures get warmer , but glaciers also depend on
02:24	how much precipitation they get each year . If less
02:27	snow accumulates glaciers lose more ice on their bottom edge
02:30	. Then they can replace at the top that precipitation
02:32	comes from the hydro sphere and its regional patterns can
02:35	depend on temperature and wind patterns over distant oceans .
02:38	So mountain landscapes have changed as climate patterns have changed
02:41	. Which ties back to the global energy budget and
02:43	insulation and the beginning of the earth . It's a
02:45	complicated problem . The terms climate change and global warming
02:48	are often used interchangeably . But even though these phenomena
02:51	are closely related , there is a difference between them
02:54	. Climate change is the change in average weather patterns
02:56	in a region over a long period of time .
02:59	These changes can be natural or anthropogenic meaning human induced
03:02	. And when I say long I mean each climate
03:04	period can last for several decades or longer . For
03:07	example there was a little ice age that happened from
03:10	1300 to 18 50 C . E . Mountain glaciers
03:13	expanded worldwide and mean annual temperatures dropped by 500.6 degrees
03:17	Celsius in the northern hemisphere . That's a 550 year
03:20	climate pattern , which then changed to a different one
03:23	. On the other hand , global warming is the
03:25	increase in the average surface temperature of our planet .
03:27	In our current period of global warming there's been a
03:30	well documented rise of average temperatures around the globe since
03:33	the Industrial Revolution in the 17 and 18 hundreds .
03:36	So when scientists , our leaders talk about global warming
03:38	there almost exclusively referring to this recent warming which comes
03:41	from human activities that increase greenhouse gas emissions like carbon
03:44	dioxide , methane and nitrous oxide , they trap solar
03:47	energy . So more heat is held in the atmosphere
03:50	. That additional energy is changing not only the average
03:52	temperature , but also climate processes within the atmosphere and
03:55	oceans . These include more extreme storms , heat waves
03:58	, droughts , changing regional temperature and precipitation patterns that
04:02	cause vegetation zones to shift and glaciers to melt ,
04:04	which results in sea level rise and changing coastlines .
04:07	Essentially when the planet gets warmer climates change , we
04:10	know the earth has had many different climates , thanks
04:12	to paleo climatologists who study past climate through proxy data
04:16	or data that provides clues about the past . Comparing
04:19	multiple proxies , gives us a more complete picture of
04:21	what happened and helps us anticipate the changes we need
04:24	to prepare for . For example , they used tree
04:26	rings that show dry and wet years , fossilized bugs
04:29	that tell us about moisture and temperature levels of bygone
04:31	ecosystems or deep sea sedimentary records that reveal the oceans
04:35	passed like the deep sea sedimentary record shows that the
04:38	earth overall had one of two extreme climates and glaciers
04:41	advanced and retreated across the earth at least 28 times
04:44	during the past 2.6 million years . We can see
04:47	that when glaciers advance in the climate is colder ,
04:49	glaciation occurs and sea levels drop and when the climate
04:53	is warmer , glacier's retreat and sea levels rise ,
04:55	ushering in an interglacial period , Which is what we're
04:58	in right now , one of the most useful kinds
05:00	of proxy data for atmospheric conditions and how climates changed
05:03	year to year . Our ice core data from ice
05:06	, we can extract the chemical composition of past atmospheres
05:09	using special drills , paleo climatologists have extracted long tubes
05:12	of ice from ice sheets and alpine glaciers all over
05:15	the world and estimated climate's going back at least 400,000
05:18	years . Let's go to the thought bubble . On
05:20	the top is fresh snow that fell this year and
05:22	the year before and the year before that Underneath is
05:25	the snow that fell when Marco Polo travelled the Silk
05:28	Road and beneath that , when the Buddha gained enlightenment
05:31	and the deepest layers were laid down long before recorded
05:33	history . The very bottom of ice sheets in places
05:36	like Greenland and Antarctica have snow that fell before the
05:39	beginning of the last ice age , 115,000 years ago
05:42	or more , just like snow on a sidewalk ,
05:44	can get compressed by boots into sheets of slippery ice
05:47	. The snow and ice sheets is compacted into huge
05:50	solid masses and buried in each layer of ice is
05:53	evidence of past atmospheric conditions . Tiny air bubbles which
05:57	act like time capsules . Once an ice core has
05:59	moved from the field to the lab , scientists use
06:02	isotope dating to tell whether the carbon dioxide in those
06:04	frozen bubbles was released from burning materials like wood or
06:07	coal in the little sphere , or if it was
06:09	airborne during a nuclear explosion or if it was part
06:12	of the natural cycling of carbon paleo . Climatologists have
06:15	collected polar ice core samples and analyzed historical air bubbles
06:18	from Greenland and Antarctica , tropical glaciers in the mountains
06:21	of the Andes , in kenya and mid latitude glaciers
06:23	in the alps and Himalayas . When all these data
06:26	are lined up , scientists can compare them with each
06:28	other and see atmospheric trends , which in turn shows
06:31	climate change over thousands of years . Analysis shows that
06:34	it can take just a few decades to change from
06:36	colder to warmer climate patterns that might not sound fast
06:39	, but when you're a 4.5 billion year old planet
06:42	like the Earth , that's nothing thanks thought bubble by
06:45	analyzing proxy data like bubbles in ice cores , we
06:48	know the Earth's climate has changed significantly many times .
06:51	As geographers , let's go deeper into why these drastic
06:54	changes happen . Based on that proxy data , paleo
06:56	climatologists hypothesized that climates changed because of any combination of
07:00	several driving forces . First past climates could have changed
07:04	because of orbital causes like changes in the shape of
07:06	the earth's orbit , its tilt on its axis and
07:08	the time of year when the sun is closest to
07:10	the earth . Like calculations by the mathematician Milutin Milinkevich
07:13	show that lots of glacial cycles occur every million years
07:16	. Second volcanic activity can release enormous amounts of volcanic
07:20	dust into the stratosphere . Strong winds spread that dust
07:23	around the world darken the skies and reduce the amount
07:25	of insulation that can reach the surface , which lowers
07:28	temperatures . This is related to the albedo effect or
07:30	the amount of sunlight a surface reflects back into space
07:33	. Volcanic dust and even the color of surfaces change
07:36	. Earth's albedo . White surfaces like ice reflect the
07:39	sun's energy , creating a cooling effect . So when
07:42	there's less ice , the opposite happens , darker surfaces
07:45	, absorb sunlight and warm the surface of the earth
07:47	. Similarly , when something big like an asteroid strikes
07:50	, it can cause an impact winter like volcanic activity
07:54	. A big impact throws dust and debris into the
07:56	air , blocking out insulation and lowering temperatures . Such
08:00	an impact may have caused the extinction of the dinosaurs
08:02	65 million years ago . Another reason that climate change
08:05	is when continents and oceans get rearranged , like when
08:08	the isthmus of Panama formed , it broke the connection
08:10	between the Atlantic and Pacific Oceans , which redirected ocean
08:13	circulation and created the Gulf Stream . This changed how
08:16	moisture and ocean currents moved around the globe , which
08:18	, as we know , contributes to climate patterns .
08:20	And finally , climates change when greenhouse gases in the
08:23	atmosphere change . We know from ice core data that
08:26	carbon dioxide levels in the atmosphere decreased when glaciers formed
08:29	during ice ages and increased during interglacial periods . However
08:33	, what's happening now is unlike anything in the past
08:36	, were in an interglacial period now , and glaciers
08:38	are melting faster than ever before . In the geologic
08:41	record , Average annual global temperatures have risen between .3°C
08:45	and .6°C, , and sea level has risen between 10
08:48	and 25 cm during the past 100 years . And
08:51	in 2016 , global atmospheric carbon dioxide levels past the
08:55	400 parts per million mark , which is higher than
08:57	at any time in the past million years . More
09:00	carbon dioxide increases the amount of heat trapped in the
09:03	lower atmosphere , enhancing the natural greenhouse effect that makes
09:06	life possible . So our climates are entering new patterns
09:09	. If this upward trend in global temperatures was caused
09:11	by natural processes alone , Geographers would consider it natural
09:15	climate change , but like I said , what's happening
09:18	now is unlike anything we've ever seen on earth .
09:20	So scientists have used multiple lines of evidence like tree
09:23	ring and ice core data , glacial retreat and sea
09:25	level rise , isotope dating changes in atmosphere and changes
09:29	in weather phenomena to study the climate . And they've
09:32	concluded that there is a greater than 95% probability that
09:35	human activities like burning fossil fuels , industrialization . Modern
09:39	agriculture and deforestation have caused most of the Earth's warming
09:42	since the mid-20th century . We are experiencing anthropogenic global
09:46	warming , but not all areas will be affected equally
09:49	by global warming and modern climate change . While materially
09:52	rich countries are the main producers of greenhouse gas emissions
09:55	. Materially poorer countries will bear most of the impacts
09:58	like becoming climate refugees , people being forced to flee
10:01	their homes for safer places . Thousands of low lying
10:04	islands and coastal cities face a threat of rising sea
10:06	levels by the end of the 21st century , when
10:08	sea levels are predicted to have risen 26 to 77
10:11	centimetres , That's pretty significant considering over half of the
10:15	world's people live within 100 km of coastline . For
10:18	example , located halfway between Australia and Hawaii care ,
10:21	Abbas has 33 atolls that sit less than two m
10:24	above sea level and average only a few 100 m
10:26	wide . The government of Carrabba's is planning a two
10:29	phase migration with dignity and has purchased several 1000 acres
10:32	of land in Fiji as a potential resettlement location for
10:35	its 102,000 residents . But migration with dignity isn't an
10:39	option for all countries and communities . For some places
10:42	, adaptation is the only option like building seawalls or
10:45	raising streets and homes and for some , that will
10:47	mean moving to higher elevations after the flooding without government
10:50	support for the process , flooding from sea level rise
10:52	is just one of many changes that we can anticipate
10:55	. Other places . For example , will experience drier
10:58	conditions with the potential for droughts , heatwaves and wildfires
11:01	. The current ways the earth's climate is changing because
11:03	of global warming will affect all of us as individuals
11:06	. So it's our collective responsibility to pay attention and
11:09	take action . Here's the thing about human induced climate
11:12	change . Knowing that we humans are the main cause
11:14	means it's also in our power to try and stop
11:17	it . We still have a small window of time
11:19	to work together and aggressively reduce our emissions to save
11:22	communities around the world from disaster . To do that
11:25	, our individual choices can make a difference . But
11:27	we also have to hold corporations and governments responsible for
11:30	the policies and large scale emissions that affect our atmosphere
11:33	and climate . This will ensure safer , healthier and
11:36	more biodiverse futures for the next generation who inherit our
11:39	planet . I know the problem of global warming may
11:41	sound overwhelming . You're not alone , but from decades
11:44	of science , we know what the problem is and
11:47	what the solutions are . It's now just about finding
11:49	ways to successfully integrate them into society in future episodes
11:53	will continue to examine how geography can help us work
11:55	on the problems that pop up where climate change intersects
11:58	with society . This has been the focus of my
12:00	research for the last several years and even though it's
12:03	an urgent area of work , it's also incredibly motivating
12:06	and exciting to be a part of finding the solutions
12:09	. Many maps and borders represent modern geopolitical divisions that
12:12	have often been decided without the consultation permission or recognition
12:16	of the land's original inhabitants . Many geographical place names
12:19	also don't reflect the indigenous or aboriginal peoples languages .
12:22	So we at Crash Course want to acknowledge these people's
12:24	traditional and ongoing relationship with that land and all the
12:27	physical and human geographical elements of it . We encourage
12:30	you to learn more about the history of the place
12:31	you call home through resources like native land dot C
12:34	A . And by engaging with your local indigenous and
12:36	aboriginal nations through the websites and resources . They provide
12:39	thanks for watching this episode of Crash Course Geography which
12:42	is filmed that the team Sandoval Pierce studio and was
12:44	made with the support of all these nice people .
12:47	If you want to help keep Crash Course free for
12:49	everyone forever , you can join our community on Patreon

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