In a study published on July 22, 2011 in the journal Science, Danish scientists report that massive extinctions occurred some 250 million years ago, due to a huge release of methane gas from the ocean floor, in a scenario that they say could parallel the path of climate change on Earth today.

http://www.physorg.com/news/2011-07-paleoecologists-mass-extinction-due-huge.html
http://www.sciencemag.org/content/333/6041/430
http://www.ibtimes.com/articles/184790/20110721/mass-extinction-earth-burp-carbon-methane-emission.htm

A meeting hosted in New Zealand, co-chaired with Mexico and South Africa on July 25 and 26, 2011, brings together international senior climate change negotiators in an effort to develop greenhouse gas monitoring methods for individual countries, which will be presented at the December summit in South Africa.

http://english.peopledaily.com.cn/90001/90777/90855/7448742.html,
http://english.cntv.cn/20110722/112012.shtml