Observational evidence

I had a conversation recently with someone who claimed that "global warming theory" is not supported by observational evidence. It's true that on any given day or week in your own neighborhood, what you see cannot necessarily be linked to climate change, as weather and climate occur on two entirely different scales. Weather is short-term while climate trends are detected over much longer periods (like 30 years at minimum) so particular weather events are not really evidence of global warming, but the longer-term patterns are.

I see plenty of observational evidence around the world that's being reported on longer term patterns. For example, in today's news, Europe's Worst Drought In 100 Years Is Getting Worse says that England is the driest it's been since 1910 and the warmest since 1659.

For more on recent climate trends, see NOAA: 2010 Tied For Warmest Year on Record.