7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 1/16
Global warming is the rise in the average temperature of Earth's atmosphere and oceans since
the late 19th century and its projected continuation. Since the early 20th century, Earth's mean
surface temperature has increased by about 0. !" #1.$ !%&, ith about to(thirds of the increaseoccurring since 190.)2* +arming of the climate system is uneuivocal, and scientists are more
than 90- certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation.)*)$*)/*)* hese
findings are recognied by the national science academies of all major industrialied nations.)3*)4*
"limate model projections ere summaried in the 2003 %ourth 4ssessment 5eport #45$& by
the 6ntergovernmental 7anel on "limate "hange #67""&. hey indicated that during the 21st
century the global surface temperature is li8ely to rise a further 1.1 to 2.9 !" #2 to /.2 !%& fortheir loest emissions scenario and 2.$ to .$ !" #$. to 11./ !%& for their highest.)* he ranges
of these estimates arise from the use of models ith differing sensitivity to greenhouse gas
concentrations.)9*)10*
%uture arming and related changes ill vary from region to region around the globe.
)11*
heeffects of an increase in global temperature include a rise in sea levels and a change in the
amount and pattern of precipitation, as ell a probable epansion of subtropical deserts.)12*
+arming is epected to be strongest in the 4rctic and ould be associated ith the continuing
retreat of glaciers, permafrost and sea ice. :ther li8ely effects of the arming include a morefreuent occurrence of etreme(eather events including heat aves, droughts and heavy
rainfall, ocean acidification and species etinctions due to shifting temperature regimes. Effects
significant to humans include the threat to food security from decreasing crop yields and the lossof habitat from inundation.)1*)1$*
7roposed policy responses to global arming include mitigation by emissions reduction,
adaptation to its effects, and possible future geoengineering. ;ost countries are parties to the<nited =ations %rameor8 "onvention on "limate "hange #<=%"""&,)1/* hose ultimateobjective is to prevent dangerous anthropogenic #i.e., human(induced& climate change.)1* 7arties
to the <=%""" have adopted a range of policies designed to reduce greenhouse gas
emissions)13*>10)1*)19*)20*>9 and to assist in adaptation to global arming.)13*>1)20*>10)21*)22* 7arties to the<=%""" have agreed that deep cuts in emissions are reuired,)2* and that future global arming
should be limited to belo 2.0 !" #. !%& relative to the pre(industrial level.)2*)?* 5eports
published in 2011 by the <nited =ations Environment 7rogramme )2$* and the 6nternationalEnergy 4gency)2/* suggest that efforts as of the early 21st century to reduce emissions may be
inadeuate to meet the <=%"""'s 2 !" target.
Contents
• 1 :bserved temperature changes
• 2 6nitial causes of temperature changes #eternal forcings&
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 2/16
o 2.1 @reenhouse gases
o 2.2 7articulates and soot
o 2. Solar activity
• %eedbac8
• $ "limate models
• / :bserved and epected environmental effects
o /.1 =atural systems
o /.2 Ecological systems
o /. Aarge(scale and abrupt impacts
• :bserved and epected effects on social systems
o .1 %ood security
o .2 Babitat inundation
• 3 5esponses to global arming
o 3.1 ;itigation
o 3.2 4daptation
• Cies on global arming
o .1 @lobal arming controversy
o .2 7olitics
o . 7ublic opinion
o .$ :ther vies
• 9 Etymology
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 3/16
• 10 See also
• 11 =otes
• 12 "itations
• 1 5eferences
• 1$ %urther reading
• 1/ Eternal lin8s
Observed temperature changes
;ain article> 6nstrumental temperature record
he increase in ocean heat content is much larger than any other store of energy in the EarthDsheat balance over the to periods 191 to 200 and 199 to 200, and accounts for more than
90- of the possible increase in heat content of the Earth system during these periods.)2*
o millennia of mean surface temperatures according to different reconstructions from climate
proies, each smoothed on a decadal scale, ith the instrumental temperature record overlaid in
blac8.
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 4/16
he Earth's average surface temperature rose by 0.3$0.1 !" over the period 190F200/. he
rate of arming over the last half of that period as almost double that for the period as a hole
#0.10.0 !" per decade, versus 0.030.02 !" per decade&. he urban heat island effect is verysmall, estimated to account for less than 0.002 !" of arming per decade since 1900.)23*
emperatures in the loer troposphere have increased beteen 0.1 and 0.22 !" #0.22 and
0.$ !%& per decade since 1939, according to satellite temperature measurements. "limate proies sho the temperature to have been relatively stable over the one or to thousand years before
1/0, ith regionally varying fluctuations such as the ;edieval +arm 7eriod and the Aittle 6ce
4ge.)2*
he arming that is evident in the instrumental temperature record is consistent ith a iderange of observations, as documented by many independent scientific groups.)29* Eamples
include sea level rise #ater epands as it arms&,)0* idespread melting of sno and ice,)1*
increased heat content of the oceans,)29* increased humidity,)29* and the earlier timing of spring events,)2* e.g., the floering of plants.)* he probability that these changes could have occurred
by chance is virtually ero.)29*
5ecent estimates by =4S4's @oddard 6nstitute for Space Studies #@6SS& and the =ational
"limatic Gata "enter sho that 200/ and 2010 tied for the planet's armest year since reliable,idespread instrumental measurements became available in the late 19th century, eceeding
199 by a fe hundredths of a degree.)$*)/*)* Estimates by the "limatic 5esearch <nit #"5<&
sho 200/ as the second armest year, behind 199 ith 200 and 2010 tied for third armestyear, hoever, Hthe error estimate for individual years ... is at least ten times larger than the
differences beteen these three years.H)3* he +orld ;eteorological :rganiation #+;:&
statement on the status of the global climate in 2010 eplains that, Hhe 2010 nominal value of
I0./ !" ran8s just ahead of those of 200/ #I0./2 !"& and 199 #I0./1 !"&, although thedifferences beteen the three years are not statistically significant...H)*
=:44 graph of @lobal 4nnual emperature 4nomalies 19/0F2012, shoing the El =iJo(
Southern :scillation
emperatures in 199 ere unusually arm because global temperatures are affected by the El
=iJo(Southern :scillation #E=S:&, and the strongest El =iJo in the past century occurred during
that year.)9* @lobal temperature is subject to short(term fluctuations that overlay long term trendsand can temporarily mas8 them. he relative stability in temperature from 2002 to 2009 is
consistent ith such an episode.)$0*)$1* 2010 as also an El =iJo year. :n the lo sing of the
oscillation, 2011 as an Aa =iJa year as cooler but it as still the 11th armest year since
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 5/16
records began in 10. :f the 1 armest years since 10, 11 ere the years from 2001 to
2011. :ver the more recent record, 2011 as the armest Aa =iJa year in the period from 19/0
to 2011, and as close to 1993 hich as not at the loest point of the cycle.)$2*
emperature changes vary over the globe. Since 1939, land temperatures have increased about
tice as fast as ocean temperatures #0.2/ !" per decade against 0.1 !" per decade&.)$*
:ceantemperatures increase more sloly than land temperatures because of the larger effective heat
capacity of the oceans and because the ocean loses more heat by evaporation.)$$* he northernhemisphere arms faster than the southern hemisphere because it has more land and because it
has etensive areas of seasonal sno and sea(ice cover subject to ice(albedo feedbac8 . 4lthough
more greenhouse gases are emitted in the =orthern than Southern Bemisphere this does notcontribute to the difference in arming because the major greenhouse gases persist long enough
to mi beteen hemispheres.)$/*
he thermal inertia of the oceans and slo responses of other indirect effects mean that climate
can ta8e centuries or longer to adjust to changes in forcing. "limate commitment studies indicate
that even if greenhouse gases ere stabilied at 2000 levels, a further arming of about 0./ !"#0.9 !%& ould still occur .)$*
Initial causes of temperature changes (external forcings)
;ain article> 4ttribution of recent climate change
@reenhouse effect schematic shoing energy flos beteen space, the atmosphere, and earth's
surface. Energy echanges are epressed in atts per suare meter #+Km2&.
his graph, 8non as the Leeling "urve, shos the increase of atmospheric carbon dioide
#":2& concentrations from 19/F200. ;onthly ":2 measurements display seasonal oscillations
in an upard trendM each year's maimum occurs during the =orthern Bemisphere's late spring,and declines during its groing season as plants remove some atmospheric ":2.
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 6/16
he climate system can respond to changes in external forcings.)$3*)$* Eternal forcings can
HpushH the climate in the direction of arming or cooling. )$9* Eamples of eternal forcings
include changes in atmospheric composition #e.g., increased concentrations of greenhousegases&, solar luminosity, volcanic eruptions, and variations in Earth's orbit around the Sun.)/0*
:rbital cycles vary sloly over tens of thousands of years and at present are in an overall cooling
trend hich ould be epected to lead toards an ice age, but the 20th century instrumentaltemperature record shos a sudden rise in global temperatures.)/1*
Greenhouse gases
;ain articles> @reenhouse gas, @reenhouse effect, 5adiative forcing, and "arbon dioide inEarth's atmosphere
he greenhouse effect is the process by hich absorption and emission of infrared radiation by
gases in the atmosphere arm a planet's loer atmosphere and surface. 6t as proposed by
Noseph %ourier in 12$ and as first investigated uantitatively by Svante 4rrhenius in 19.)/2*
4nnual orld greenhouse gas emissions, in 200/, by sector.
?ubble diagram shoing the share of global cumulative energy(related carbon dioide emissionsfor major emitters beteen 190(2003.)/*
=aturally occurring amounts of greenhouse gases have a mean arming effect of about !"
#/9 !%&.)/$*)"* he major greenhouse gases are ater vapor , hich causes about F30- of the
greenhouse effectM carbon dioide #":2&, hich causes 9F2-M methane #"B$&, hich causes $F 9-M and oone #:&, hich causes F3-.)//*)/*)/3* "louds also affect the radiation balance through
cloud forcings similar to greenhouse gases.
Buman activity since the 6ndustrial 5evolution has increased the amount of greenhouse gases inthe atmosphere, leading to increased radiative forcing from ":2, methane, tropospheric oone,"%"s and nitrous oide. he concentrations of ":2 and methane have increased by - and
1$- respectively since 13/0.)/* hese levels are much higher than at any time during the last
00,000 years, the period for hich reliable data has been etracted from ice cores.)/9*)0*)1*)2* Aess direct geological evidence indicates that ":2 values higher than this ere last seen about 20
million years ago.)* %ossil fuel burning has produced about three(uarters of the increase in ":2
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 7/16
from human activity over the past 20 years. he rest of this increase is caused mostly by changes
in land(use, particularly deforestation.)$*
:ver the last three decades of the 20th century, gross domestic product per capita and populationgroth ere the main drivers of increases in greenhouse gas emissions.)/* ":2 emissions are
continuing to rise due to the burning of fossil fuels and land(use change.)*)3*>31
Emissions can beattributed to different regions, e.g., see the figure opposite. 4ttribution of emissions due to land(
use change is a controversial issue.)*)9*>29
Emissions scenarios, estimates of changes in future emission levels of greenhouse gases, have
been projected that depend upon uncertain economic, sociological, technological, and natural
developments.)30* 6n most scenarios, emissions continue to rise over the century, hile in a fe,emissions are reduced.)31*)32* %ossil fuel reserves are abundant, and ill not limit carbon emissions
in the 21st century.)3* Emission scenarios, combined ith modelling of the carbon cycle, have
been used to produce estimates of ho atmospheric concentrations of greenhouse gases might
change in the future. <sing the si 67"" S5ES Hmar8erH scenarios, models suggest that by the
year 2100, the atmospheric concentration of ":2 could range beteen /$1 and 930 ppm.
)3$*
hisis an increase of 90F2/0- above the concentration in the year 13/0.
he popular media and the public often confuse global arming ith oone depletion, i.e., the
destruction of stratospheric oone by chlorofluorocarbons.)3/*)3* 4lthough there are a fe areas of lin8age, the relationship beteen the to is not strong. 5educed stratospheric oone has had a
slight cooling influence on surface temperatures, hile increased tropospheric oone has had a
somehat larger arming effect.)33*
4tmospheric ":2 concentration from /0,000 years ago to near present, using ice core proy
data and direct measurements
Particulates and soot
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 8/16
Ship trac8s over the 4tlantic :cean on the east coast of the <nited States. he climatic impactsfrom particulate forcing could have a large effect on climate through the indirect effect.
@lobal dimming, a gradual reduction in the amount of global direct irradiance at the Earth's
surface, as observed from 191 until at least 1990.)3* he main cause of this dimming is
particulates produced by volcanoes and human made pollutants, hich eerts a cooling effect byincreasing the reflection of incoming sunlight. he effects of the products of fossil fuel
combustion F ":2 and aerosols F have largely offset one another in recent decades, so that net
arming has been due to the increase in non(":2 greenhouse gases such as methane.)39* 5adiative forcing due to particulates is temporally limited due to et deposition hich causes
them to have an atmospheric lifetime of one ee8. "arbon dioide has a lifetime of a century or
more, and as such, changes in particulate concentrations ill only delay climate changes due to
carbon dioide.)0*
6n addition to their direct effect by scattering and absorbing solar radiation, particulates have
indirect effects on the radiation budget.)1* Sulfates act as cloud condensation nuclei and thus lead
to clouds that have more and smaller cloud droplets. hese clouds reflect solar radiation moreefficiently than clouds ith feer and larger droplets, 8non as the omey effect.)2* his effect
also causes droplets to be of more uniform sie, hich reduces groth of raindrops and ma8es
the cloud more reflective to incoming sunlight, 8non as the 4lbrecht effect.)* 6ndirect effects
are most noticeable in marine stratiform clouds, and have very little radiative effect onconvective clouds. 6ndirect effects of particulates represent the largest uncertainty in radiative
forcing.)$*
Soot may cool or arm the surface, depending on hether it is airborne or deposited.
4tmospheric soot directly absorb solar radiation, hich heats the atmosphere and cools thesurface. 6n isolated areas ith high soot production, such as rural 6ndia, as much as /0- of
surface arming due to greenhouse gases may be mas8ed by atmospheric bron clouds.)/*
+hendeposited, especially on glaciers or on ice in arctic regions, the loer surface albedo can alsodirectly heat the surface.)* he influences of particulates, including blac8 carbon, are most
pronounced in the tropics and sub(tropics, particularly in 4sia, hile the effects of greenhouse
gases are dominant in the etratropics and southern hemisphere.)3*
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 9/16
Satellite observations of otal Solar 6rradiance from 1939F200.
"ontribution of natural factors and human activities to radiative forcing of climate change.)*
5adiative forcing values are for the year 200/, relative to the pre(industrial era #13/0&.)* he
contribution of solar irradiance to radiative forcing is /- the value of the combined radiativeforcing due to increases in the atmospheric concentrations of carbon dioide, methane and
nitrous oide.)9*
Solar activity
;ain articles> Solar variation and Solar ind
Since 193, output from the Sun has been precisely measured by satellites.)90* hese
measurements indicate that the Sun's output has not increased since 193, so the arming during
the past 0 years cannot be attributed to an increase in solar energy reaching the Earth. 6n thethree decades since 193, the combination of solar and volcanic activity probably had a slight
cooling influence on the climate.)91*
"limate models have been used to eamine the role of the sun in recent climate change.)92* ;odels are unable to reproduce the rapid arming observed in recent decades hen they only
ta8e into account variations in solar output and volcanic activity. ;odels are, hoever, able tosimulate the observed 20th century changes in temperature hen they include all of the most
important eternal forcings, including human influences and natural forcings.
4nother line of evidence against the sun having caused recent climate change comes from
loo8ing at ho temperatures at different levels in the Earth's atmosphere have changed. )9*
;odels and observations sho that greenhouse arming results in arming of the loer
atmosphere #called the troposphere& but cooling of the upper atmosphere #called the
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 10/16
stratosphere&.)9$*)9/* Gepletion of the oone layer by chemical refrigerants has also resulted in a
strong cooling effect in the stratosphere. 6f the sun as responsible for observed arming,
arming of both the troposphere and stratosphere ould be epected.)9*
eedbac!
;ain article> "limate change feedbac8
Sea ice, shon here in =unavut, in northern "anada, reflects more sunshine, hile open oceanabsorbs more, accelerating melting.
he climate system includes a range of feedbacks hich alter the response of the system tochanges in eternal forcings. 7ositive feedbac8s increase the response of the climate system to an
initial forcing, hile negative feedbac8s reduce the response of the climate system to an initial
forcing.)93*
here are a range of feedbac8s in the climate system, including ater vapor , changes in ice(albedo #sno and ice cover affect ho much the Earth's surface absorbs or reflects incoming
sunlight&, clouds, and changes in the Earth's carbon cycle #e.g., the release of carbon from soil&.
)9* he main negative feedbac8 is the energy hich the Earth's surface radiates into space asinfrared radiation.)99* 4ccording to the Stefan(?oltmann la, if temperature doubles, radiated
energy increases by a factor of 1 #2 to the $th poer&.)100*
%eedbac8s are an important factor in determining the sensitivity of the climate system to
increased atmospheric greenhouse gas concentrations. :ther factors being eual, a higherclimate sensitivity means that more arming ill occur for a given increase in greenhouse gas
forcing.)101* <ncertainty over the effect of feedbac8s is a major reason hy different climate
models project different magnitudes of arming for a given forcing scenario. ;ore research isneeded to understand the role of clouds)93* and carbon cycle feedbac8s in climate projections.)102*
he 67"" projections given in the lede span the Hli8elyH range #greater than - probability, based on epert judgement&)$* for the selected emissions scenarios. Boever, the 67""'s
projections do not reflect the full range of uncertainty.)10* he loer end of the Hli8elyH rangeappears to be better constrained than the upper end of the Hli8elyH range.)10*
Climate models
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 11/16
;ain article> @lobal climate model
"alculations of global arming prepared in or before 2001 from a range of climate models under
the S5ES 42 emissions scenario, hich assumes no action is ta8en to reduce emissions and
regionally divided economic development.
7rojected change in annual mean surface air temperature from the late 20th century to the middle
21st century, based on a medium emissions scenario #S5ES 41?&.)10$* his scenario assumes that
no future policies are adopted to limit greenhouse gas emissions. 6mage credit> =:44 @%GA.)10/*
4 climate model is a computeried representation of the five components of the climate system>4tmosphere, hydrosphere, cryosphere, land surface, and biosphere.)10* Such models are based on
physical principles including fluid dynamics, thermodynamics and radiative transfer . here can
be components hich represent air movement, temperature, clouds, and other atmospheric propertiesM ocean temperature, salt content, and circulationM ice cover on land and seaM the
transfer of heat and moisture from soil and vegetation to the atmosphereM chemical and biological
processesM and others.
4lthough researchers attempt to include as many processes as possible, simplifications of theactual climate system are inevitable because of the constraints of available computer poer and
limitations in 8noledge of the climate system. 5esults from models can also vary due to
different greenhouse gas inputs and the model's climate sensitivity. %or eample, the uncertaintyin 67""'s 2003 projections is caused by #1& the use of multiple models )10* ith differing
sensitivity to greenhouse gas concentrations,)103* #2& the use of differing estimates of humanities'
future greenhouse gas emissions,)10* #& any additional emissions from climate feedbac8s thatere not included in the models 67"" used to prepare its report, i.e., greenhouse gas releases
from permafrost.)10*
he models do not assume the climate ill arm due to increasing levels of greenhouse gases.
6nstead the models predict ho greenhouse gases ill interact ith radiative transfer and other physical processes. :ne of the mathematical results of these comple euations is a prediction
hether arming or cooling ill occur.)109*
5ecent research has called special attention to the need to refine models ith respect to the effect
of clouds)110* and the carbon cycle.)111*)112*)11*
;odels are also used to help investigate the causes of recent climate change by comparing the
observed changes to those that the models project from various natural and human(derived
causes. 4lthough these models do not unambiguously attribute the arming that occurred from
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 12/16
approimately 1910 to 19$/ to either natural variation or human effects, they do indicate that the
arming since 1930 is dominated by man(made greenhouse gas emissions.)/0*
he physical realism of models is tested by eamining their ability to simulate contemporary or past climates.)11$*
"limate models produce a good match to observations of global temperature changes over the
last century, but do not simulate all aspects of climate.)11/* =ot all effects of global arming are
accurately predicted by the climate models used by the 67"". :bserved 4rctic shrin8age has been faster than that predicted.)11* 7recipitation increased proportional to atmospheric humidity,
and hence significantly faster than global climate models predict.)113*)11*
Observed and expected environmental effects
;ain article> Effects of global arming
HGetectionH is the process of demonstrating that climate has changed in some defined statistical sense, ithout providing a reason for that change. Getection does not imply attribution of the
detected change to a particular cause. H4ttributionH of causes of climate change is the process of
establishing the most li8ely causes for the detected change ith some defined level ofconfidence.)119* Getection and attribution may also be applied to observed changes in physical,
ecological and social systems.)120*
Sparse records indicate that glaciers have been retreating since the early 100s. 6n the 19/0s
measurements began that allo the monitoring of glacial mass balance, reported to the +orld
@lacier ;onitoring Service #+@;S& and the =ational Sno and 6ce Gata "enter #=S6G"&
"atural systems
;ain article> 7hysical impacts of climate change
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 13/16
@lobal arming has been detected in a number of natural systems. Some of these changes are
described in the section on observed temperature changes, e.g., sea level rise and idespread
decreases in sno and ice etent.)121* ;ost of the increase in global average temperature since themid(20th century is, ith high probability,)G* attributable to human(induced changes in
greenhouse gas concentrations.)122*
Even ith policies to reduce emissions, global emissions are still epected to continue to gro
over time.)12*
6n the 67"" %ourth 4ssessment 5eport, across a range of future emission scenarios, model(based
estimates of sea level rise for the 21st century)12$* range from 0.1 to 0./9 m. hese estimates,
hoever, ere not given a li8elihood due to a lac8 of scientific understanding, nor as an upper bound given for sea level rise. :n the timescale of centuries to millennia, the melting of ice
sheets could result in even higher sea level rise. 7artial deglaciation of the @reenland ice sheet,
and possibly the +est 4ntarctic 6ce Sheet, could contribute $F metres #1 to 20 ft& or more to
sea level rise.)12/*
"hanges in regional climate are epected to include greater arming over land, ith most
arming at high northern latitudes, and least arming over the Southern :cean and parts of the
=orth 4tlantic :cean.)12* Sno cover area and sea ice etent are epected to decrease, ith the
4rctic epected to be largely ice(free in September by 203.)12*
6t is calculated that, ith high statistical confidence, certain eather events, such as the heat
aves in eas and the 200 European heat ave, ould not have occurred ithout global
arming. Etremely hot outliers, defined as three standard deviations from climatology records,no cover about 10- of the land surface and, under present trends, ould be the norm by 20/0.
hese temperatures are epected to eacerbate the hydrological cycle, ith more intense
droughts and floods.
)123*
he effect on hurricane activity is less certain.
)12*
#cological systems
;ain article> "limate change and ecosystems
6n terrestrial ecosystems, the earlier timing of spring events, and poleard and upard shifts in
plant and animal ranges, have been lin8ed ith high confidence to recent arming.)121* %utureclimate change is epected to particularly affect certain ecosystems, including tundra,
mangroves, and coral reefs.)12* 6t is epected that most ecosystems ill be affected by higher
atmospheric ":2 levels, combined ith higher global temperatures.)129* :verall, it is epected
that climate change ill result in the etinction of many species and reduced diversity ofecosystems.)10*
Gissolved ":2 increases ocean acidity. his process is 8non as ocean acidification and has
been called the Heually evil tinH of global climate change.)11* 6ncreased ocean aciditydecreases the amount of carbonate ions, hich organisms at the base of the marine food chain,
such as foraminifera, use to ma8e structures they need to survive. he current rate of ocean
acidification)12* is many times faster than at least the past 00 million years, hich included four
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 14/16
mass etinctions that involved rising ocean acidity, such as the 7ermian mass etinction, hich
8illed 9/- of marine species. ?y the end of the century, acidity changes since the industrial
revolution ould match the 7alaeocene(Eocene hermal ;aimum, hich occurred over /000years and 8illed /F/0- of benthic foraminifera.)1*
$arge%scale and abrupt impacts
"limate change could result in global, large(scale changes in natural and social systems.)1$* oeamples are ocean acidification caused by increased atmospheric concentrations of carbon
dioide, and the long(term melting of ice sheets, hich contributes to sea level rise.)1/*
Some large(scale changes could occur abruptly, i.e., over a short time period, and might also beirreversible. 4n eample of abrupt climate change is the rapid release of methane from
permafrost, hich ould lead to amplified global arming. )1* Scientific understanding of abrupt
climate change is generally poor .)13* Boever, the probability of abrupt changes appears to be
very lo.)1*)1* %actors that may increase the probability of abrupt climate change include higher
magnitudes of global arming, arming that occurs more rapidly, and arming that is sustainedover longer time periods.)1*
Observed and expected effects on social systems
%urther information> Effects of global armingOSocial systems and 5egional effects of globalarmingO5egional impacts
Culnerability of human societies to climate change mainly lies in the effects of etreme(eather
events rather than gradual climate change.)19* 6mpacts of climate change so far include adverseeffects on small islands,)1$0* adverse effects on indigenous populations in high(latitude areas,)1$1*
and small but discernable effects on human health.)1$2* :ver the 21st century, climate change isli8ely to adversely affect hundreds of millions of people through increased coastal flooding,
reductions in ater supplies, increased malnutrition and increased health impacts.)1$* ;osteconomic studies suggest losses of orld gross domestic product #@G7& for this)clarification needed *
magnitude of arming.)1$$*)1$/*
ood security
See also> "limate change and agriculture
<nder present trends, by 200, maie production in Southern 4frica could decrease by up to 0-
hile rice, millet and maie in South 4sia could decrease by up to 10-.)1$* ?y 200, yields indeveloping countries could decrease by 10- to 2/- on average hile 6ndia could see a drop of
0- to $0-.)1$3* ?y 2100, hile the population of three billion is epected to double, rice and
maie yields in the tropics are epected to decrease by 20F$0- because of higher temperatures
ithout accounting for the decrease in yields as a result of soil moisture and ater suppliesstressed by rising temperatures.)1*
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 15/16
%uture arming of around !" #by 2100, relative to 1990F2000& could result in increased crop
yields in mid( and high(latitude areas, but in lo(latitude areas, yields could decline, increasing
the ris8 of malnutrition.)1$0* 4 similar regional pattern of net benefits and costs could occur foreconomic #mar8et(sector & effects.)1$2* +arming above !" could result in crop yields falling in
temperate regions, leading to a reduction in global food production. )1$*
&abitat inundation
%urther information> Effects of climate change on humansOGisplacementKmigration
See also> "limate refugee
6n small islands and megadeltas, inundation as a result of sea level rise is epected to threatenvital infrastructure and human settlements.)1$9*)1/0* his could lead to issues of statelessness for
populations in countries such as the ;aldives and uvalu)1/1* and homelessness in countries ith
lo lying areas such as ?angladesh.
'esponses to global warming
itigation
;ain article> "limate change mitigation
5educing the amount of future climate change is called mitigation of climate change.)citation needed * he 67"" defines mitigation as activities that reduce greenhouse gas #@B@& emissions, or
enhance the capacity of carbon sin8s to absorb @B@s from the atmosphere.)1/2* ;any countries,
both developing and developed, are aiming to use cleaner, less polluting, technologies.)3*>192)1/* <se of these technologies aids mitigation and could result in substantial reductions in ":2
emissions. 7olicies include targets for emissions reductions, increased reneable energy
commercialisation, energy conservation, and increased energy efficiency. Studies indicate
substantial potential for future reductions in emissions.)1/$*
6n order to limit arming to ithin the loer range described in the 67""'s HSummary 5eport
for 7olicyma8ersH)1//* it ill be necessary to adopt policies that ill limit greenhouse gas
emissions to one of several significantly different scenarios described in the full report.)1/* his
ill become more and more difficult ith each year of increasing volumes of emissions and evenmore drastic measures ill be reuired in later years to stabilie a desired atmospheric
concentration of greenhouse gases. Energy(related carbon(dioide #":2& emissions in 2010 ere
the highest in history, brea8ing the prior record set in 200.)1/3*
daptation
;ain article> 4daptation to global arming
:ther policy responses include adaptation to climate change. 4daptation to climate change may be planned, either in reaction to or anticipation of climate change, or spontaneous, i.e., ithout
7/21/2019 Global Warming
http://slidepdf.com/reader/full/global-warming-56d96df91c4c4 16/16
government intervention.)1/* 7lanned adaptation is already occurring on a limited basis.)1/$* he
barriers, limits, and costs of future adaptation are not fully understood.)1/$*
4 concept related to adaptation is Hadaptive capacity,H hich is the ability of a system #human,natural or managed& to adjust to climate change #including climate variability and etremes& to
moderate potential damages, to ta8e advantage of opportunities, or to cope ith conseuences.)1/9* <nmitigated climate change #i.e., future climate change ithout efforts to limit greenhouse
gas emissions& ould, in the long term, be li8ely to eceed the capacity of natural, managed andhuman systems to adapt.)10*
Top Related