235, A large nuclear war vculd cause the injection of substantial quantities ofnitrogen oxides into the upper atmosplrere, especially if a nultitude of explosionsin the rnegaton range r,rere to occur. These oxides ffou1d then reach the ozone fayerin the stratosnhere and might, through chemical reactions, partiar-1y destroy it ina fei'/ months. A reriod of about 5 years is believed to be iequired to restore thelayer again. Since ozone is an effective trarrier to solar uttraviolet radiation,a depletion of the ozone colunn wourd. result in an increase of this radiation atthe surface of the earth. unfortunately, the fufl t,iorogical irnplications of anincreased ul-traviolet rad-iation tc ecosysterns at various latitudes are not knoryr.Hor^rever ' the incidence of skin cancer is thought to be related to the anount ot.u-Itraviclet radiation received. Mutations in plents and animals rnight alsoinc rease . 235- The extent to which the refease of a given quantity of nitrogen oxides wcurddeplete the ozone Layer is at present not enbirely clear. A 1975 ;tudy by theunited states l\rational Acad.emy of sciences reported a 30 to f0 per ceni reductionof the ozone layer if a total yield of l0,O0O Mt. r.rere to be exploded. Laterinvestigations have 1ed to a better und.erstanding of the cheraistry involved. rt isnov believed that such a heavy depr-etion courd occur onfy if most of the totalyield derived from multi-negaton veapons. ?37. A sizable change of ozone coneentration in the stratosphere would seriouslyaffect stratospheric heating. This in turn wou-ld change tenperature conditionsin the troposphere and hence cause possibre clirnatic changes- at the earthrssurface. r,arge amounts of dust inJected in the atmosphere rnight further add tothese charges, ft has been estimated that l0,0OO Mt. vould potl_l_,t" th"stratcsDhere vith 107-19E 1..rtr. of -stFl^iet I .injectei by the erupti;;;;"1:"o:i.li"iii"';r*l;r:'";:;*::";:i3";.':"::::ed to besmal'ler in tropical and subtropical zoiEs and targer at higher latitudes. rnthe latter regions, howeverr.even sma11 changes, such as a cooling of 10 C.rIrouldhave serious consequences. (rt is esti[ated that the Krakatoa event at mostcaused a ternperatu"e reduction of O.5o C, over a fev years.) The lu C, coolingcould severely hamper wheat growing in Canada and parts of the USSR, for instance,clue to a reduction of the nrmber of frost-free days. Although the recovery trmeassociated r'rit h possible g1obal clirnatic changes due to a large nuclear varvould probably be only a fev years, present knowledge is insuiticient to d.efiniteryru]e out nore persistent effects. Social, economic and politicaf effects
**Analysis**
The text primarily discusses the potential environmental and climatic consequences of a large nuclear war, specifically focusing on the depletion of the ozone layer, changes in temperature, and potential effects on agriculture and ecosystems. The text also touches on the uncertainty and potential long-term effects of such an event. Given this focus on the environmental and ecological implications, I hypothesize that the most fitting category is likely to be related to natural resources and environment, possibly combined with agriculture and forestry.

**Category**
Natural resources and environment, Agriculture, forestry and fishing