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Climate change
t’snosecretthatEarthisintrouble,
anditislargelyourfault.Sincethe
IndustrialRevolutionwehavebeen
pumpingsomuchcarbondioxide
andothergreenhousegasesintotheatmosphere
thatourplanetisrapidlywarming.Theraceis
ontokeeptherisetounder1.5degreesCelsius
(2.7degreesFahrenheit),butitisa targetweare
predictedtomiss.Theconsequencescouldbe
dire:risingsealevels,watershortages,increased
migrationandthepossibilityofmorefrequentwars
aswebattleeachotherforresources.
Itcouldturnouttobethegreatestfoewehave
everfaced,anditislargelyofourownmaking,
yetthereisstilltimetoturnthingsaround.Public
awarenessoftheissuehasneverbeenhigher,
andgovernmentsandindividualsalikeareslowly
startingtowakeuptotheirresponsibilities– but
willitallbetoolate?Partofthetroubleisthatthe
climateofa planetisanincrediblycomplexsystem
witha lotofmovingparts.Throughoutitshistory
Earthhaswarmedandcooledallonitsown,
alternatingbetweeniceagesandmoretemperate
phases.Howdoweteaseoutourcontributionfrom
thesebackgroundupsanddowns?AccordingtoDr
NicholasAttree,a researchfellowattheUniversity
ofStirling,wecoulddoa lotworsethantolookat
ourneighbours.“WhatweseeonEarth
isnaturalclimatecycles,plushuman
inf luence,”hesays.“Lookingatthe
cyclesofotherplanetsmeans
I
we can better understand our cycles and better
understand our inf luence.”
Attree has been looking closely at Mars’ past
climate. It is the most explored planet in the Solar
System, with a host of active rovers trawling the
surface and satellites whizzing around it examining
the ground from on high. We have discovered
that,likeEarth,Marscyclesthroughperiodswith
differentclimaticconditions.Thereasonissimple:
gravity.UnlikeEarth,MarshasnolargeMoonfor
stability.Combinethatwiththefactitiscloserto
theSolarSystem’sbigboys– JupiterandSaturn–
anditgetsbulliedbyitsgiantneighbours.Being
pulledthiswayandthatleadstoa changeinMars’
obliquity– thetiltoftheaxisonwhichitrotates.
ItalsochangestheshapeofMars’orbitovertime,
makingissuccessivelymoreandlesscircular.
Theupshotisthattheintensityofsunlightfalling
onMarsisconstantlychanging,butina regular
way.Asinglecyclelaststensofthousandsofyears.
Attreehasbeenlookingatwhethertheseclimatic
moodswingscouldhavelefta detectablesignature
onMarstoday.“Duringwarmerperiodsthere
wouldbeanincreasedheatf lowundertheMartian
surface,”hesays.“We’vemodelledhowthatheat
wouldbuildupovertime.”InNovemberlastyear
hepublisheda predictionthatNASA’sInSight
maybeabletodetectthatexcessheat.
InSightlandedontheRedPlanetin
November 2018 andisequipped
witha self-hammering‘mole’
VENUS
BY THE NUMBERS
Average temperature –
about twice as hot as
an oven
Venus’ albedo – it reflects
69 per cent of sunlight
Days for Venus to rotate,
leading to a static climate
Atmospheric pressure
compared to Earth – same
as being one kilometre (0.62
miles) underwater
of the Venusian atmosphere
is carbon dioxide
Winds move 60-times faster
than Venus spins
464°C
0.69
243
92
96.5%
60
Venus’ age when runaway
greenhouse effects began
600
million years
Above:The
thickcloudson
Ve nu spreve nt
usseeingthe
surfacein
visiblelight
Below:The
HP3probeon
NASA’sInSight
missionis
measuring
Mars’
internalheat
© NASA
A regular
cycleof ice ages
Earth’stiltchanges over time,
ochanging levels of
rgyhitting the planet.
erageincreases and
htice reflects more
htback into space,
herreducing the
emperature.
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leadingt
solarener
Icecove
thebrig
sunligh
furth
te
Heat flow probe
HP^3 instrument
© NASA