All About Space - UK (2020-02)

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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