A Habi­tat for Hu­man­ity

The at­mos­phere is chang­ing. What is caus­ing it – and what comes next?

Asian Geographic - - Front Page - Cli­mate change is the defin­ing chal­lenge of our time. Our abil­ity to rise to this chal­lenge is only as good as our knowl­edge of the science of the sit­u­a­tion. Here are the es­sen­tials that you need to know.

planet is un­der­go­ing un­ex­pected and com­pli­cated – but un­der­stand­able – changes. Sun­light pen­e­trat­ing the Earth’s at­mos­phere is be­ing trapped, and the world is stor­ing heat en­ergy more than it used to. Why is this change oc­cur­ring? It is pri­mar­ily caused by ris­ing lev­els of sev­eral green­house gases – pri­mar­ily car­bon diox­ide (CO2), fol­lowed by meth­ane, which are part of the at­mos­phere shroud­ing the planet. The more of these gases (and water vapour) are in the at­mos­phere, the more ef­fi­ciently the sun’s heat is cap­tured.

These gases are im­por­tant parts of bi­o­log­i­cal sys­tems. In fact, you – and all of the other an­i­mals on the planet – are re­leas­ing CO2 with ev­ery ex­ha­la­tion. We breathe in oxy­gen to al­low us to burn su­gars within our cells, and these are bro­ken down into water and CO2 mol­e­cules. Each CO2 mol­e­cule is com­prised of one car­bon atom bound to two oxy­gen atoms, whereas water (H2O) is two hy­dro­gen atoms bound to one oxy­gen atom.

Mir­ror­ing this process, but not nec­es­sar­ily bal­anc­ing it, is the col­lec­tion of CO2 by plants. Pow­ered by sun­light, plants col­lect and com­bine CO2 with water to cre­ate the very mass of life. This in­cludes the su­gars that we break down to fuel our lives. Your body, the blades of grass, the wood of the forests, and al­most all other liv­ing things are formed from that which is pro­duced by green plants dur­ing pho­to­syn­the­sis.

Un­der­stand­ing the flow of car­bon atoms through the planet is es­sen­tial to un­der­stand­ing our chang­ing at­mos­phere. Car­bon is re­leased into the at­mos­phere from biomass when it is bro­ken down by fire or de­com­po­si­tion. You could think of our

The

cells’ di­ges­tion of food as tiny bi­o­log­i­cal ovens burn­ing su­gar. Sim­i­larly, car­bon is re­leased from biomass dur­ing for­est fires or when it is bro­ken down by fun­gus or other or­gan­isms.

How­ever, the amount of car­bon that is mo­bile within the at­mos­phere is only a frac­tion of what is ac­tu­ally on the planet. The el­e­ment of car­bon com­bines with other atoms to form dif­fer­ent com­pounds, and only a small por­tion of the planet’s car­bon is in the at­mos­phere as CO2.

More than half of the Earth’s car­bon is present in rocks, such as lime­stone (bound to cal­cium and oxy­gen) or sand­stone (pri­mar­ily sil­i­con). About a quar­ter is stored in the Earth’s oceans, and a minis­cule por­tion trav­els into space by way of as­tro­nau­tics or me­te­ors. The long and the short of it is that the rapid changes to Earth’s cli­mate are pri­mar­ily a story of veg­e­ta­tion clear­ing and the dis­cov­ery of fos­sil en­ergy.

The fos­sils and the forests

An­cient fos­silised car­bons are the crit­i­cal piece to the puz­zle: They un­der­pin our mod­ern civil­i­sa­tion and have granted us in­cred­i­ble re­serves of en­ergy. These fos­sil fu­els – coal, oil, and nat­u­ral gas – are the stored biomass or out­gassing of bi­o­log­i­cal ma­te­rial that has some­how been en­cap­su­lated on a vast scale. We dig them up, burn them, and re­lease them into the at­mos­phere where they act as green­house gases. Over­all, there is prob­a­bly 20 times as much car­bon stored as fos­sil fu­els than there is liv­ing plant mat­ter on Earth. These an­cient or­ganic ma­te­ri­als have been housed in the rocks of the Earth for mil­lions of years. In some forms, such as coal, you can clearly iden­tify the leaves of plants that have ac­cu­mu­lated into coal beds.

As these ma­te­ri­als have been brought into fur­naces to power en­gines, and into lab­o­ra­to­ries to cre­ate new com­pounds such as plas­tic, we have ex­tracted the en­ergy to build the man­made world around us. When these en­er­gies are used to clear forests and drain swamps, the car­bon stored in or­ganic mat­ter be­gins to de­com­pose, or is burnt, and it finds its way into the at­mos­phere. That, in a nut­shell, is the foun­da­tion of the cur­rent cri­sis.

Past changes

There is a clear cor­re­la­tion be­tween lev­els of CO2 in the at­mos­phere and the fluc­tu­a­tions in tem­per­a­ture of the planet. The Earth has ex­pe­ri­enced pe­ri­ods of great cold and great heat in its ge­o­log­i­cal past, but it has been rel­a­tively sta­ble for al­most two mil­lion years.

There is a clear cor­re­la­tion be­tween lev­els of CO2 in the at­mos­phere and the fluc­tu­a­tions in tem­per­a­ture of the planet

The cli­mate of the last 1,000 years, and prior to the wide-scale burn­ing of fos­sil fu­els in the 1800s dur­ing the In­dus­trial Rev­o­lu­tion, has been part of a nat­u­ral warm­ing pe­riod af­ter the most re­cent Ice Age.

Over the last half a mil­lion years, CO2 has shifted be­tween 180 and 280 parts per mil­lion. Since 1950, pri­mar­ily due to the burn­ing of fos­sil fu­els, it has sky­rock­eted to just over 400 parts per mil­lion, and it is not lev­el­ling out.

If this con­tin­ues, we will ex­pe­ri­ence a hot­ter cli­mate in the years to come. We will need to find ways to ei­ther store CO2, or mit­i­gate the green­house ef­fect to avoid this un­cer­tain, and in­creas­ingly omi­nous, fu­ture.

The dis­cov­ery

Un­der­stand­ing global cli­mate gases is built upon upon care­ful mea­sure­ments and ex­per­i­men­ta­tion across dis­ci­plines in­clud­ing me­te­o­rol­ogy, chem­istry, ge­ol­ogy, as­tron­omy, oceanog­ra­phy, botany, engi­neer­ing, and physics. The Swiss nat­u­ral­ist de Saus­sure’s 1767 ex­per­i­ment with so­lar ovens led to Fourier’s 1824 re­al­i­sa­tion that the Earth could warm by sun­light’s heat en­ergy fail­ing to re­flect back into space, devel­op­ing fur­ther to pro­duce Ar­rhe­nius’s 1859 cal­cu­la­tions of cli­mate change based on at­mo­spheric gases.

Pre­ci­sion mea­sure­ment of at­mo­spheric CO2 be­gan in 1958 on the peak of the Hawai­ian vol­cano Mauna Loa; 100,000 years

of world­wide en­ergy-re­lated CO2 emis­sions, com­pared to

17 per­cent in 1990 Sev­eral tens of bil­lions of dol­lars will be needed an­nu­ally to help devel­op­ing coun­tries tran­si­tion to low-car­bon and cli­mate-re­silient economies, with USD40 bil­lion an­nu­ally for adap­ta­tion in Asia and the Pa­cific alone 20 mil­lion Bangladeshis would be dis­placed by a one me­tre rise in sea level by 2050 More than 60 per­cent of the re­gion’s pop­u­la­tion works in agri­cul­ture, fish­eries, and forestry, which are the sec­tors most at-risk to cli­mate change

60%

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