1986 air chernobylnuclearaccident chornobylʹ climaticchanges environmentalaspects environmentaldegradation environmentalexposure globalenvironmentalchange globalwarming mathematicalmodels models nuclearenergy nuclearenergyandmeteorology nuclearindustry politicalaspects pollution radioactivefallout radioactivepollution radioactivepollutionofsoils radioactivepollutionofwater radioactivewastedisposal radioisotopes renewableenergysources restorationecology safetymeasures theoretical transporttheory ukraine wn420s4331995