Here's a graph showing the extent of arctic sea ice as measured directly and indirectly for the last several hundred years:
Solid red line is the reconstructed 40 year smoothed, late-summer Arctic sea ice extent from Kinnard et al. (2011). Shaded area shows 95% confidence interval. Blue dashed line shows modern observations.
This graphic is from Skeptical Science, where you can also download a higher res version and learn more about the background for these data. Also, on that page is a link to a large number of useful graphics related to climate change.
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Soon To Be Hurricane Isaac
Time to start watching the Arctic Sea Ice breakup. This happens every year, but as you know, the total amount of ice left each summer has been reducing, and the "old ice" which forms a basis for the arctic ice refreeze is disappearing.
You want to look away as this Andrew Bolt post comes off the rails, crashes and burns, but you can't.
Here are a few links with that graphic:
http://www.skepticalscience.com/Arctic-sea-ice-hockey-stick-melt-unprec…
http://skepticalscience.com/past-Arctic-sea-ice-extent.htm
http://skepticalscience.com/graphics.php
Global warming is a lie because I hate Al Gore!
Global warming is a lie because scientists are stupid!
Global warming is a lie because my car needs gas!
Global warming is a lie because Lush Rimballs says so!
Global warming is a lie because it goes against my politics!
Global warming is a lie because even if it is true, who doesn't like warm weather!
Global warming is a lie because it was cold in Winnipeg last winter!
Global warming is a lie because only Lord Jeebus can change the weather!
Answer that, you smarty pants libs!