“So­lar geo­engi­neer­ing alone could not sta­bilise the world’s cli­mate. For that, we must both stop pump­ing car­bon pol­lu­tion into the at­mos­phere and learn how to re­move what is al­ready there. That is why emis­sions cuts should re­ceive the lion’s share of reso

Financial Mirror (Cyprus) - - FRONT PAGE -

The last time the at­mos­phere held as much car­bon diox­ide as it does to­day was about three mil­lion years ago – a time when sea lev­els were 10-30 me­tres higher than they are now. Cli­mate mod­els have long strug­gled to duplicate those large fluc­tu­a­tions in sea lev­els – un­til now. In­deed, for the first time, a high-qual­ity model of Antarc­tic ice and cli­mate has been able to sim­u­late th­ese large swings. That is smart science, but it brings dev­as­tat­ing news.

The new model shows that melt­ing in Antarc­tica alone could in­crease global sea lev­els by as much as one me­ter by the end of this cen­tury – well above prior es­ti­mates. Worse, it sug­gests that even ex­tra­or­di­nary suc­cess at cut­ting emis­sions would not save the West Antarc­tic Ice Sheet, lock­ing in even­tual sea-level in­creases of more than five me­ters. As lit­tle as one me­ter could put at risk en­tire cities, from Mi­ami to Mum­bai, and cause enor­mous eco­nomic dis­rup­tion.

We need to turn down the heat – and fast. To this end, albedo mod­i­fi­ca­tion – a kind of geo­engi­neer­ing in­tended to cool the planet by in­creas­ing the re­flec­tiv­ity of the earth’s at­mos­phere – holds tremen­dous prom­ise.

In­ject­ing syn­thetic aerosols that re­flect sun­light into the strato­sphere, for ex­am­ple, could help counter the warm­ing caused by green­house gases. The mech­a­nism is sim­i­lar to wear­ing a white shirt in the sum­mer: white re­flects sun­light and cools what is un­der­neath, whereas darker colours ab­sorb sun­light and heat.

To be sure, even in the best-case sce­nario, so­lar geo­engi­neer­ing alone could not sta­bilise the world’s cli­mate. For that, we must both stop pump­ing car­bon pol­lu­tion into the at­mos­phere and learn how to re­move what is al­ready there. That is why emis­sions cuts should re­ceive the lion’s share of re­sources de­voted to com­bat­ing cli­mate change.

But, as the re­cent study shows, emis­sions cuts alone can­not save the West Antarc­tic Ice Sheet and pre­vent a dras­tic sea-level rise. If they are pur­sued in con­junc­tion with mod­er­ate albedo mod­i­fi­ca­tion, how­ever, there is a chance of halt­ing ris­ing tem­per­a­tures, helping to keep the world un­der 1.5 de­gree Cel­sius above pre-in­dus­trial lev­els, the more am­bi­tious target agreed at the Paris cli­mate talks last De­cem­ber. (It should be noted that, given car­bon-cy­cle feed­backs, such as the thaw­ing of per­mafrost, there is a chance that the world would face a 1.5C rise, even if emis­sions were elim­i­nated to­day.)

Most of the world’s state-of-the-art cli­mate mod­els have ex­plored albedo mod­i­fi­ca­tion, and each of them has found that the process does have the po­ten­tial to mit­i­gate cli­mate change. Be­yond lim­it­ing to­tal warm­ing, it can help to check the rise in peak tem­per­a­tures, de­creas­ing the risk of de­struc­tive heat waves. And it seems to be par­tic­u­larly ef­fec­tive at re­duc­ing ex­treme rain­fall, which holds pro­found im­pli­ca­tions for min­imis­ing flood dam­age.

Albedo mod­i­fi­ca­tion re­mains uncertain and risky, ow­ing partly to a dearth of or­gan­ised re­search into the sub­ject. And, in fact, albedo mod­i­fi­ca­tion would un­doubt­edly make some things worse. But there is not a sin­gle cli­mate model run that shows that a mod­er­ate in­ter­ven­tion would make any re­gion worse off over­all. More­over, the large po­ten­tial up­side, mea­sured in tril­lions of dol­lars, con­trasts with low di­rect costs – in the sin­gle-digit bil­lions for full-scale de­ploy­ment. In fact, albedo mod­i­fi­ca­tion is so cheap that di­rect costs will not be the de­cid­ing is­sue. In­stead, it is a risk-risk trade-off – one that will re­quire more re­search to as­sess.

Given the lack of knowl­edge, no sen­si­ble per­son would push for de­ploy­ing albedo mod­i­fi­ca­tion to­day. But it would make no sense to ig­nore its po­ten­tial. Af­ter all, no one would

Newspapers in English

Newspapers from Cyprus

© PressReader. All rights reserved.