Via Tamino, I learned of a not particularly large, $250 bet with Scott Supak over whether there will be statistically significant warming in 25 years starting in 1997 (details posted at Roy Spencer's blog).
This is an update to a bet offer that Michaels' newsletter made in 1998 for a 10 year period. James Annan learned of that offer in 2005 and tried to accept, but the new editor Chip Knappenberger pulled a Lindzen (defined here) and declined to keep that bet. Seems like a pretty good bet for Scott despite starting in the 1997-1998 El Nino, some uncertainty about defining statistical signficance, and despite using HADCRUT which as I understand it leaves out the rapidly-warming high Arctic.
I btw have my own series of bets with up to $9,000 on the line, starting with 2007 five-year average and ending with 2017, 2022, and 2027 five-year averages. So far it's not going well for me, but it's early days. Best case scenario is at the end of 2029, I've lost my shirt. Worst case scenario is I've won every bet. Almost-worst case scenario is that statistical or a real temporary lull cost me on the 10-year bet (which will slow down efforts to address the problem) while I win on the 20.