Apart from temperature and storm events, the biggest measurable change is in the ocean

In May 2013 the USA's National Oceanic & Atmospheric Administration (NOAA) revealed that the daily mean concentration of carbon dioxide in the atmosphere of Mauna Loa, Hawaii has surpassed 400 parts per million (ppm). This is the first time this has happened since measurements began in 1958. The world average is 394ppm.

Exactly how much is that? Well, it's the highest level in 800,000 years as can be seen in this great YouTube graphic, courtesy of NOAA.

So what does this all mean? It explains why we've had a steady increase in temperatures, and many more extreme weather events than previous decades. The ABC's Catalyst aired ‘Extreme Weather' on 4 July, which discusses these extremes of heat and cold over the last few years and explains how and why they come about.

This video from Berkeley Earth also shows the last 200 years of land temperature rise. My favourite part is that it shows the temperature readings starting in the British Colonies and spreading across the world. Australia's data either wasn't there, wasn't consistent or wasn't deemed accurate enough till the 1840s.

The Berkeley Earth data was gathered by Richard Muller, Professor of Physics at the University of California at Berkeley. He was one of the more qualified climate change sceptics. He gathered that data intending to prove that the climate change camp was manipulating data to show a rapid recent increase in temperature. He found out the climate scientists were wrong - the temperature change he found was actually higher. In the face of such overwhelming evidence, he changed his opinion and is now a staunch supporter of climate change.

Apart from temperature and storm events, the biggest measurable change is in the ocean. Below are two great TED talks about the impact of climate change on the ocean.

In the first one, Jame Balog gives a great TED talk about loss of Arctic and glacial ice. The talk is from a few years ago and it's now been turned into a movie documentary called Chasing Ice. Check out the trailer at http://www.chasingice.com/.

In the second TED talk, US Rear-Admiral David Titley makes some interesting strategic points about global warming and rising sea levels (you can skip to 15.30 to get to the juicy strategic stuff). He calls climate change "one of the pre-eminent challenges of this century". I tend to feel that by the time the military are talking about something openly, they've probably been talking about it privately for 20 years.

Some other great sites;

Australian Academy of Science http://www.science.org.au/nova/environment/climate-change/

Eureka Award winning Skeptical Science http://www.skepticalscience.com/