Oct 24 was 350 day, with people in 181 countries around the world held 5,200 events to highlight the importance of the number 350.

350 stands for 350 parts per million of carbon dioxide in the atmosphere.  This is the levelof carbon dioxide that scientists say we should aim for to avoid catastrophic climate change.

At the begining of the industrial revolution in 1850, before we started burning coal, oil and gas a huge levels, the amount of carbon dioxide in the air was around 280 parts per million (ppm).  In the 160 years since, humans have burnt so much fossil fuels and chopped down so much forest, that there are 385ppm in the atmosphere.

Yes, that is already over the safe level of 350, so we actually need to work to bring the level down below 350ppm by restoring forests and drastically lowering carbon emissions.

To see all the wonderful photos of 350 around the world goto: www.350.org

In Sydney various climate action groups marked the day with different events:

350 at Sydney Opera House

Ice berg built outside the Newtown Neighbourhood Centre

350 at Clovelly, Sydney

350 at Middle Harbour and Mosman public schools

School Children at Rozelle

350 at Vinson Massif, Antarctica