What Is the Purpose of Chemtrails?

It's easy to think the worse-- but we really just have idea what they are doing. There's just too much lack of info and disinfo on this topic.

One possible good thing they are doing would be to try to mitigate the effects of global warming, by putting up particles to block the sun. But I doubt they are doing anything completely beneficial.

It's worth noting, that chemtrails are something done by our government, to the benefit on someone or something in this country. 

In the simplest terms, perhaps they are simply trying to alter the weather, to help the growth of crops-- by promoting rain or such. Weather modification is undoubtedly real. But wouldn't the temptation be huge, to adversely affect the weather sometimes, and negatively effect crops by inducing drought. People who did this would be able to make a killing in the stock market.

But we just don't know.  Almost certainly, it is not being done for the benefit of most people, otherwise it wouldn't be done in such secrecy.

So, what are the chemtrail options?

1) spraying compounds to counter-act global warming
2) weather modification for the benefit of farmers
3) weather modification with ulterior motives
4) military mapping of US topography
5) chemical agents to make Americans more sick
6) biological agents to make Americans more sick
7) chemical agents to dumb down Americans
8) chemical agents to enhance or mimic global warming
9) some combination of the above?

I really just don't know what to believe on this topic.