Global warming
When people burn stuff like the aerosols, for example smoke, are bad because when people breath them they make people ill. But some people say that in a climate change emergency the Earth could be kept cool by reflecting some sunlight back into space, for example by putting aerosols very high in the air or making clouds whiter. They say this would give more time to do a proper fix. This is so easy and cheap that even a middle-size country could do it. But there are a lot of problems: for example it might be good for that country but bad for some other countries.