First a couple of local ones, in May:
Then, this one looks interesting: The World Climate Conference, in Geneva at the end of August. It looks like most of the program will be invited, but they will be accepting abstracts for a poster session. Given that the theme is to do with how climate information is generated and used, it sounds very appropriate.
Followed almost immediately by EnviroInfo2009, in Berlin, in September. I guess the field I want to name “Climate Informatics” would be a subfield of environmental informatics. Paper deadline is April 6.
Finally, there’s the biggy in Copenhagen in December, where, hopefully, the successor to the Kyoto agreement will be negotiated.