(Well, at least the version that everyone knows it as- just simply "global warming")
Global Warming is the increase in the average global temperature of the Earth. It has been measured in recent decades and is now being predicted far into the future.
The Greenhouse effect is based on the fact that Greenhouse gasses like CFC's in aerosols, carbon dioxide, carbon monoxide, and sulfur rise into the atmosphere and linger there. As they linger there, they allow shorter wavelength light to pass through, but, longer infrared waves are absorbed by the gasses. These gasses also reflect more heat than our atmosphere does on its own, instead of heat radiating back into space, it comes back and heats us up even more!
These greenhouse gasses are produced every time you turn on a car, light a match, use spray-paint, or even breathe! I'm not telling you to stop breathing, the ecosystem can handle normal breathing, just not the other things we're pumping into it, and how we're using resources. In New Zealand, farmers deforested entire areas and replaced the trees with cows. Wow there are more cows, whoop-de freakin' do! Well guess what, each cow that replaced the oxygen producing tree, now emits carbon dioxide and methane into the air by farting a whole bunch!
I digress, you may be wondering how increased temperature gets rid of snow. if your thinking, in the winter, it's cold enough to cancel out the effects of global warming... No, it's not. the temperature change, however slight it is, doesn't allow snow to reach the ground as snow. it all melts on it's way down and just becomes rain.
Then it gets worse. because there is no snow on the ground, the Earth heats up a little bit more. Your snow-less town may not effect the Global temperature, but it will make it harder for snow to come down later in the winter. usually a major portion of the sunlight that comes down to Earth is reflected back into space by snow, but now, it is being absorbed by black asphalt and heating, creating a cycle.
There is a simple experiment you can try (if you are lucky enough to have snow). take a white cloth, a black cloth, and some other colors you may have. lay them all out in separet sections of the snow (give them about an inch or two between each other). then all you do is wait. Which one melts through the snow the fastest.
I bet it was the black cloth. the black cloth absorbed more of the sun's radiation than it reflected back. the same effect happens when there isn't any snow and the black asphalt on the road heats up, giving you less of a chance for the snow to stick when and if it ever comes.