The atmospheric chemistry would be upset by cutting out sunlight. It would be like a nuclear winter and could last for tens of thousands of years. These comets are 200-300km (186 miles) in diameter they are sheer monsters and could sterilise the earth if we are hit by one.
Heat stress â Another reason for rose leaves turning yellow is the rose bush is under some sort of stress. A common cause of stress is heat stress. The rose bush turns yellow and drops its foliage in an effort to cool down in the case of heat stress.
Pests or disease â Roses with yellow leaves can also be a sign that the rose has a pest or disease. There are many rose pests and roses diseases that cause yellow leaves. To help determine which it may be, look carefully on the rose bush for other signs of damage or symptoms of disease.