I'm from the future.  I'm from your future.  With amazing technologies, we have discovered how to transgress time itself with words and change the very fabric of the earth.  But... But people do not believe that we should.  They say we should leave the past as it is, accept what is and what has happened and move on.  Leave the Earth to rot with neglect and misuse. 
    Some friends and I don't think so.  We managed to get the technology to send this message.  We can't say if it will make it through or if people will even believe it, but it is the best we can do.  We believe it is our duty and responsibility to warn and inform you.  Those problems you think are minor? Well, they aren't.  The ice has melted, the sea engulfed entire countries, and diseases that we couldn't cure fast enough ran rampant across the earth, killing anything that moved.  Plants withered and burned and the remaining humans banded together in a struggle to survive, forced to stay out of the intensified sun by the near complete lack of an ozone layer.  Nights are below freezing and days are well above boiling.  It is a miracle that anyone could survive there at all.
    Eventually we managed to scrape together technology and work with it.  We had been using specially designed buildings for quite a time to grow food and preserve water, so we were able to transfer that technology to the transportation we gathered and when the temperature was just starting to warn, we escaped into space.
    We have not found anything that we can use to sustain life yet.  We know about those other biosphere plants, but there is no way we will reach them anytime soon.  That light speed technology you were considering?  We haven't created it yet.  This voyage will likely continue until we run out of fuel, and we will live out the rest of our lives in this strange gravity and this small ship.
    So you see why I have turned to you.
    You can change everything for us.  /Help/ the Earth, don't destroy it.  Stop killing all the animals and plant species, each of which play a vital role in the biosphere of the Earth.  Leave what should be left alone alone and find alternative energy and resources.  Everything you do changes the lives of your children and their children and generations of your family. 
    Please, I only have 5 minutes to save the world, and you are my best hope.