This global event will take place on October 15, 2009. For this year, the topic is Climate change. One day. One issue. Thousands of voices.

Here's how to join:

• Register your blog.
• Get a badge for your blog.
• Promote via Twitter or Facebook.
• Submit your post on October 15, 2009.

Here's a clip about this year's topic from the Blog Action Day homepage.

Climate change affects us all and it threatens more than the environment. It threatens to cause famine, flooding, war, and millions of refugees.

Given the urgency of the issue of climate change and the upcoming international climate negotiations in Copenhagen this December, we think the blogosphere has the unique opportunity to mobilize millions of people around expressing support for finding a sustainable solution to the climate crisis.