CONSESUS ON CLI­MATE CHANGE

Jamaica Gleaner - - IN FOCUS - GUEST COLUM­NIST A. An­thony Chen

IREGARD Martin Henry as one of the bet­ter com­men­ta­tors in your news­pa­per. How­ever, in his ar­ti­cle ‘Hur­ri­canes and cli­mate change’ (The Sun­day Gleaner, Septem­ber 10, 2017), he ap­pears to have fallen into a trap set by USA rightwing think tanks scep­ti­cal of cli­mate change.

In dis­cussing the work of cli­mate-change de­nier Dr Ju­dith Curry, Mr Henry states, “A num­ber of coura­geous and ac­com­plished sci­en­tists, who are by no means flat-earth­ists, have en­dured the per­se­cu­tion to present al­ter­na­tive views. Con­sid­er­ing how much is at stake for the fu­ture of hu­mans on the planet, one would think that the sen­si­ble thing to do is to al­low a va­ri­ety of views to flour­ish, which would al­low us to pick sense out of non­sense and to chal­lenge or­tho­dox­ies in search of the real truth. This used to be the spirit of sci­ence.”

Mr Henry should re­alise that the spirit of sci­ence is ex­actly what pre­vails in con­fronting Dr Curry and oth­ers, as I will ex­plain be­low.

Let me start by stat­ing a very cru­cial piece of statis­tics: 97 per cent of the ex­perts on cli­mate change, the cli­mat­e­change sci­en­tists them­selves, agree that hu­mans have been the main cause of cli­mate change since the 1950s. (See, e.g.), Con­sen­sus on con­sen­sus: A syn­the­sis of con­sen­sus es­ti­mates on hu­man-caused global warm­ing, by John Cook, et al, in En­vi­ron­men­tal

Re­search Let­ters. This con­sen­sus is dif­fer­ent from an­other sur­vey that used non-ex­perts such as eco­nomic ge­ol­o­gists and a self-se­lected group of those who re­ject the con­sen­sus.)

Con­sen­sus is very cru­cial in the sci­en­tific process. The sci­en­tific process in the case of cli­mate change works in the fol­low­ing man­ner. Ob­served me­te­o­ro­log­i­cal data and other data called proxy data are an­a­lysed to de­ter­mine if there is a change in cli­mate, i.e., a change in long-term av­er­ages. If there is an ob­serv­able change, other anal­y­sis and com­puter ex­per­i­ments are car­ried out to de­tect the cause of cli­mate change.

HU­MANS MAIN CAUSE FOR CHANGE

Con­sen­sus is ar­rived at through peer re­view of re­search pa­pers. The fact that 97 per cent of the ex­perts whose pa­pers have been re­viewed agree that hu­mans have been the main cause of cli­mate change since 1950 is re­mark­able, given the chaotic na­ture of the cli­mate sys­tem. The other three per cent who do not agree have ei­ther found that their anal­y­sis does not de­tect a hu­man sig­na­ture or are swayed by other con­sid­er­a­tions, such as eco­nomics (in the pay of fos­sil fuel com­pa­nies), in­stincts, or re­li­gious be­liefs.

That up to three per cent of sci­en­tists may not have found a ma­jor hu­man sig­na­ture in their data is not sur­pris­ing, given the chaotic na­ture of cli­mate, and I stressed the ‘may’ be­cause other con­sid­er­a­tions could have in­flu­enced their de­ci­sion.

How­ever, the fact that there is 97 per

cent con­sen­sus that hu­man fac­tor has been a ma­jor cause of cli­mate change is more than suf­fi­cient for gen­eral ac­cep­tance, and I will say more about this in the next para­graph. But I want to point out, that in ad­di­tion, peer re­views of Dr Curry’s re­search and that of other cli­mate-change de­niers have pointed out flaws in their con­clu­sions, one of which I will men­tion at the end of this ar­ti­cle for those in­ter­ested.

And while it would be ac­cept­able that three per cent of sci­en­tists did not de­tect a ma­jor hu­man sig­na­ture in their data, what is not ac­cept­able is that they are say­ing the ma­jor­ity of sci­en­tists who find a hu­man sig­na­ture are not cor­rect, and it is the three per cent that is cor­rect. So let us ex­plore con­sen­sus and ac­cep­tance a lit­tle fur­ther.

Sci­en­tific con­clu­sions are ac­cepted when there is a great deal of cer­tainty. For physics sys­tems, such as the be­hav­iour of atom, the cer­tainty re­quired is ex­tremely high. For plants and an­i­mals, al­lowance has to be made for vari­a­tions, and sim­i­larly for the Earth sys­tem.

Yet there is ac­cep­tance when there is a high de­gree of con­sen­sus. Take, for in­stance, the harm­ful ef­fect of nico­tine on hu­man health. There is a mi­nor­ity of sci­en­tists who have not found a con­nec­tion be­tween nico­tine and hu­man health, but the con­sen­sus is high that this is the case. Are we to al­low cig­a­rette com­pa­nies to do as they please just be­cause a small mi­nor­ity of sci­en­tists have not found a con­nec­tion be­tween nico­tine and

hu­man health? Sim­i­larly, are we to al­low the fos­sil fuel com­pa­nies to do as they like be­cause a small mi­nor­ity of sci­en­tists do not agree that fos­sil fuel is a ma­jor con­trib­u­tor to cli­mate change, es­pe­cially when flaws can be found in their ar­gu­ments?

In spite of the sim­i­lar­ity be­tween ac­cep­tance of the ef­fect of nico­tine on hu­man health and the ef­fect of fos­sil fuel on cli­mate, I pre­fer to con­sider the sim­i­lar­ity be­tween ac­cep­tance of hu­man evo­lu­tion and the ac­cep­tance of hu­man-in­duced cli­mate change, be­cause in the

case of evo­lu­tion, all de­ci­sions are not based on sci­ence, and sim­i­larly in the case of cli­mate change.

HU­MAN EVO­LU­TION

There is a mi­nor­ity of bi­o­log­i­cal sci­en­tists and a great num­ber of lay per­sons who do not buy into hu­man evo­lu­tion, de­spite sci­en­tific ev­i­dence. Do we give equal sci­en­tific cre­dence to them as to the vast ma­jor­ity of bi­o­log­i­cal sci­en­tists who ac­cept hu­man evo­lu­tions? Do we give equal space to the be­lief of cre­ation­ists as to the sci­ence of

evo­lu­tion in sci­en­tific text­books? No, maybe in a church fo­rum, but not in a sci­ence fo­rum.

In the world of sci­ence, we ac­cept the con­sen­sus of the ma­jor­ity of bi­o­log­i­cal sci­en­tists, so sim­i­larly, we should ac­cept the 97 per cent ma­jor­ity con­sen­sus on cli­mate change and not al­low a “va­ri­ety of views to flour­ish”. I said that Mr Henry has fallen into a trap set by right-wing cli­mate-change de­niers be­cause this is the strat­egy they pur­sue. They wish us to give equal time to the scep­tics as to the ma­jor­ity of sci­en­tists.

Be­cause the stakes are so high, we can­not give equal treat­ment to mi­nor­ity cli­mate scep­tics and the ma­jor­ity cli­mate sci­en­tists, just as we can­not give equal treat­ment to white su­prem­a­cists and the Amer­i­cans of good­will who protest against them, as Pres­i­dent Trump would have us do.

BIG SWING IN CLI­MATE

Mr Henry has also quite rightly said that “over the long haul, the planet has seen many big-cli­mate swings, sev­eral in recorded his­tory”. But im­ply­ing that the present change is just such a swing is ne­glect­ing what the data are show­ing us. Proxy and in­stru­ment data show that tem­per­a­tures have never been as high over the last two mil­len­nia as it cur­rently is, so this is not a swing; it is an out­lier.

In ad­di­tion, the in­crease in tem­per­a­ture over the last 50 years has been ex­po­nen­tial, coin­cid­ing with the ex­po­nen­tial in­crease in car­bon diox­ide, and there is a well-es­tab­lished sci­en­tific con­nec­tion be­tween car­bon diox­ide and plan­e­tary tem­per­a­ture. And this brings us to one of the flaws in Dr Curry’s anal­y­sis.

Dr Curry and other cli­mat­e­change de­niers have said that their data show a pause or ‘hia­tus’ in warm­ing since 1998. The data set they use is de­rived from satel­lite data, from which they de­ter­mine lower at­mo­spheric tem­per­a­ture. They skip ocean tem­per­a­tures (which ac­counts for more than 90 per cent of the warm­ing), mea­sure­ment at the sur­face of the Earth us­ing in­stru­men­ta­tion (ther­mome­ters) and ice loss, which re­quires warm­ing.

Oth­ers who use a more com­plete data set see a con­tin­ued warm­ing. For ex­am­ple, Iselin Med­haug, et al, in the lead­ing journal, Na­ture, in May 2017 showed that “ap­par­ently con­tra­dic­tory con­clu­sions stem from dif­fer­ent def­i­ni­tions of ‘hia­tus’ and from dif­fer­ent datasets. A com­bi­na­tion of changes in forc­ing, up­take of heat by the oceans, nat­u­ral vari­abil­ity and in­com­plete ob­ser­va­tional cov­er­age rec­on­ciles mod­els and data. Com­bined with stronger re­cent warm­ing trends in newer datasets, we are now more con­fi­dent than ever that hu­man in­flu­ence is dom­i­nant in longterm warm­ing.”

And to top it all, Carl A. Mears and Frank J. Wentz, in Journal of Cli­mate in June 2017, us­ing the same satel­lite data as the scep­tics, but cor­rect­ing a prob­lem with satel­lite data, viz, drift in al­ti­tude and their or­bital hor­i­zon­tal drift, show that there was “more warm­ing than most sim­i­lar data sets con­structed from satel­lites or ra­diosonde data”. In other words, even satel­lite data showed that there was no hia­tus, agree­ing with other meth­ods of de­ter­min­ing tem­per­a­tures.

Lo­cally, the Cli­mate Stud­ies Group at Mona found that there is a warm­ing trend from 1992 to 2012, cer­tainly no hia­tus in Ja­maica. The moral of the story is that sci­ence is ob­jec­tive and cal­cu­lat­ing; it gives equal time to both sides of a de­bate if they have equal weight­ing, but in the end, it aims for con­sen­sus, which is achieved by ex­per­i­men­tal and an­a­lytic agree­ment.

AP

In th­ese Septem­ber 11 pho­tos, Larry Di­mas sur­veys his de­stroyed trailer in Immokalee, Florida. Irma badly dam­aged Di­mas’ mo­bile home and de­stroyed an­other he used for rental in­come, mak­ing his tough life even harder.

AP

De­bris sur­rounds a de­stroyed struc­ture in the af­ter­math of Hur­ri­cane Irma, last Wed­nes­day, in Big Pine Key, Forida. Any­one who suf­fered dam­age from hur­ri­canes Har­vey or Irma will be thank­ful if they have home­own­ers or wind­storm cov­er­age and flood in­sur­ance.

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