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Geography • ScienceENVIRONMENT
The planet is warming, but understanding why isn’t easy. These
12 questions and answers will help you grasp the basics.BY LAURA
ANASTASIA
Two degrees Fahrenheit.That’s roughly how much Earth’s average
temperature has risen since the 1880s. While it may not sound like
much, the change is having effects all over the globe: Ice is
melting at the North and South poles. Ocean levels are rising. In
some places, rainfall is
getting heavier; in others, droughts are becoming more
severe.
This shift in Earth’s average temperature and precipitation over
a long period of time is called climate change. (You’ve probably
also heard the term global warming. That refers to one specific
part of climate change: the increase in
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Watch a Video / / ( I ) Download Skills Sheets12 APRIL 23, 2018
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IndiaD R O U G H T
A m a n c ro s s e s a p a r c h e d w a t e r re s e r v o ir n
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C h e n n a i, o n e o f In d ia ’s
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Earth’s average temperature, which has been linked to human
activities.)
Some people don’t believe humans are causing the warming or that
it’s happening. (In a 2016 Pew Research Center survey, 20 percent
of Americans said there’s no solid proof of global warming.) But
the vast majority of climate scientists say
the problem is urgent. If dramatic steps aren’t taken, they say,
life on Earth could become very difficult.
“We built our cities, our water systems, our food systems, our
energy systems... on the assumption that you can have heat waves
and cold waves, but over time, it all averages out,” says
climate scientist Katharine Hayhoe. “That assumption was
accurate for the last few thousand years, but it doesn’t work
anymore.”
The good news is that people are working to keep the worst
effects of climate change from happening— and you can help. But
first, here’s what you need to know. —►
JUNIOR.SCHOLASTIC.COM 13
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ENVIRONMENT
W h a t a re g re e n h o u s e
gases, a n d h o w d o th e y cause g lo b a l w a rm in g ?
Greenhouse gases are invisible gases in the air that act like
the glass panes of a greenhouse, trapping some of the sun’s heat
close to Earth (see graphic, right). Some of them occur naturally
in our atmosphere. But when we burn fossil fuels (such as coal and
oil) to power homes, cars, and factories, we release even more
greenhouse gases, such as carbon dioxide.
The so-called greenhouse effect is a good thing—to a certain
extent. Without it, our planet would be a frozen wasteland. The
problem is that we are producing too much of these greenhouse
gases. Since the Industrial R evolution, the amount of carbon
dioxide in the atmosphere has increased by more than 40 percent.
That means more heat is being trapped and, as a result, Earth’s
average temperature has been rising.
2 H o w d o w e k n o w th a t h u m an a c t iv ity is re s p o
n s ib le fo r th e in c re a s e in g re e n h o u s e
gases?Carbon dioxide levels did rise and fall naturally long ago,
but those changes occurred gradually over thousands of years. Now,
through the burning of fossil fuels, humans are releasing carbon
dioxide into
the air much faster than nature has ever done, scientists say.
That explains the rapid warming better than anything else, many
scientists have concluded. Experts have also looked at the natural
factors known to affect Earth’s temperature and believe that these
factors are not changing nearly enough to cause the current
warming.
E n e r g y f r o m th e su n ( in th e fo r m o f
l ig h t a n d h e a t ) t r a v e ls
th r o u g h E a r th ’s
a tm o s p h e r e . A b o u t h a lf o f
th is e n e r g y is a b s o r b e d
b y E a r th ’s s u rfa c e .
How the Greenhouse Effect Works
C lo u d s , s n o w , la n d , a n d th e o c e a n s r e f le
c t m u c h o f th e re s t o f th e
s u n ’s e n e r g y b a c k to w a r d s p a c e .
G re e n h o u s e g a s e s t r a p s o m e o f t h a t r e f
le c te d e n e r g y
in th e a tm o s p h e r e , w a r m in g th e
p la n e t fu r th e r . T o o m u c h o f th e s e
g a s e s in th e a ir re s u lts In g lo b a l
w a r m in g .
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3 If Earth is gettingwarmer, why is it still so cold in some
places?To understand how cold weather occurs in a warming world, it
helps to know the difference between climate and weather. Weather
is what’s going on outside in a certain place on any given day. It
can change quickly and be hard to predict. Climate describes what
weather conditions are usually like in a place over a prolonged
period of time—and it changes slowly. Scientists say that Earth’s
climate has been getting hotter for decades (see chart, below).
“Two weeks of really cold temperatures don’t negate decades of
warming,” says Jake Crouch of the National Oceanic and Atmospheric
Administration.
In Canada, for example, winters are still bitterly cold—but not
as consistently cold as they used to be. The warming trend means
that the ice in the country’s outdoor skating rinks is melting
earlier in the season. Researchers estimate that the number of
outdoor ice-skating days will drop by 34 percent in Toronto and 19
percent in Calgary by 2090.
“The fact that this could be taken away and is tied to climate
has been
Som aliaD R O U G H T K ids w a it fo r a id in a re fu g e e ca
m p . M illio n s o f S om alis a re s tru g g lin g to fin d fo o
d a fte r d ro u g h t k ille d o ff th e ir c ro p s and liv e s
to c k .
a real eye-opener,’’says Colin Robertson, a Canadian geography
professor who tracks ice-skating conditions in North America.
4 1s clim ate change to blame for all the recent wild
weather?Scientists have published strong evidence that the warming
trend is making heat waves more frequent and intense. Coastal
flooding is also increasing as the oceans rise. As for
hurricanes and other storms, while climate change doesn’t
necessarily cause them, it likely makes them worse. For example,
during Hurricane Harvey last August, up to 40 percent more rain
poured down than would have if the exact same hurricane had
happened decades earlier, experts say. Climate change, says Hayhoe,
“takes the natural risks that we’ve always faced and exacerbates
them.”
Tracking the W arm ing TrendScientists began recording Earth’s
average global tem peratu re in the 1880s.Nine o f the 10 hottest
years on record took place in the 21st century. How m any have
occurred since 2010?Note: Average global temperature includes land
and ocean surface areas.
2016201520172014201020132005200919982012
SOURCE: National Oceanic and Atmospheric Administration
5 W hy are the seas rising— and how fast?Sea water levels are
rising for two main reasons. The oceans are getting warmer—and
water expands as it heats up, causing sea levels to rise. Plus,
melting glaciers and ice sheets are adding more water to the oceans
(see map, p. 16).
The seas are now rising at an average rate of about 1 foot per
century. If that were to continue, the increase would probably be
manageable, some experts —►
JUNIOR.SCHOLASTIC.COM IS
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ENVIRONMENT
say. The risk is that the rate will increase even more. Because
of the changes that have already happened, some experts fear an
eventual sea level rise of more than 20 feet. That’s enough to
flood many coastal cities, but just how long it will take to happen
is unclear. Our best bet, experts say, is to try to slow the
process of sea level rise by cutting emissions.
6 W h ic h p la c e s w ill be th e f irs t to fe e l th e e ffe
c ts o f c lim a te ch an g e?People around the world are already
feeling the effects. In Cape Town, South Africa, for example, years
of warmer weather—coupled with less rainfall—have led to three
straight years of drought. The city of 4 million people now faces a
water shortage so extreme that its water supply may run out in
2019.
In other places, too much water is the problem. Because of sea
level rise, the Marshall Islands in the Pacific Ocean flood
frequently and
Shrinking Arctic IceThe A rctic is warm ing m ore than tw ice as
fast as the rest o f the w orld, and its sea ice is disappearing.
Som e scientists pred ict A rctic sea ice will be com plete ly gone
during sum m er m onths w ith in the next generation.
could be unfit for human habitation within decades, scientists
say.
7 So w h a t ’s th e w o rs t-c a s e scen ario ?Over the next
25 or 30 years, the climate is likely to continue to warm, causing
more extreme weather, scientists say.
In the long term, if greenhouse gas emissions rise unchecked,
climate effects could become so
severe that they lead to unrest in some countries and produce
waves of refugees—as well as eventually cause a mass extinction of
both plants and animals.
8 C an th e w a rm in g b e s to p p e d ?Scientists say the
warming can be slowed to a potentially manageable pace—z/humans
stop producing greenhouse gas emissions. Some countries, such as
Sweden, have already seen their emissions fall after investing in
renewable energy. Other countries have set emissions limits for
power plants. But experts say we need to do much more to avoid the
worst effects of climate change.
9 W h a t e lse a re c o u n trie s d o in g to h e lp p re v e
n t c lim a te chan g e?Nearly all 196 countries have signed a pact
known as the Paris Agreement, which took effect in 2016. The
agreement is a vow to voluntarily limit future greenhouse gas
emissions.
The goal is to keep Earth's temperature from rising more than
3.6 degrees Fahrenheit this century.
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H ouston , TexasFLOODINGLast August, Hurricane Harvey brought
record rainfall that submerged parts of the city, including this
major highway.
That would “hold warming to something we actually can largely
adapt to without fundamental changes and impacts on our
civilization,” says Hayhoe.
Is the U.S. dropping out of the agreement?
That’s the plan, but formally exiting the deal will take a
while. Last year, President Donald Trump said that the U.S.—the
second-largest emitter of carbon dioxide after China—would withdraw
from the Paris Agreement. He says the pact imposes unfair
environmental standards on American businesses and could hurt the
economy.
However, under the rules of the deal, the soonest any country
can drop out is November 4, 2020. (That’s coincidentally the day
after the next U.S. presidential election.)
In the meantime, a growing number of U.S. cities, businesses,
universities, and individuals have pledged to reduce greenhouse
gas
emissions on their own in order to help meet the original Paris
goals.
Can we get energy without producing so
many greenhouse gases?Yes, and those alternative energy sources
may end up being cheaper than burning fossil fuels, some scientists
say. Wind turbines, solar panels, hydroelectric dams, and nuclear
power plants produce among the fewest emissions. Converting to such
power sources would be more expensive now, but ultimately they
could pay for themselves by reducing climate damage and health
problems associated with air pollution.
This is all pretty overwhelming. What
can I personally do about it?A lot, actually. You can start by
cutting greenhouse gas emissions in easy ways, like making sure the
lamps in your house use energy-
efficient bulbs and turning off the lights when you leave a
room. Also, wasting less food helps because uneaten or spoiled food
ends up in landfills and releases methane, a greenhouse gas. Walk,
bike, or opt for public transportation when possible to help curb
emissions and air pollution.
You can also try to shop at businesses that are working to
reduce their carbon dioxide emissions—and use social media to
encourage other companies to reduce their emissions as well.
Finally, share what you have learned about climate change with
your friends and family. After all, Hayhoe says, “talking about it
is one of the most important things we can do.” ♦
Additional reporting by TheNewYork
Times and Tricia Culligan
CORE QUESTION What are the main ways climate change is affecting
people?
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