Here's an interesting 
BBC report on 
the role that litigation might play in the climate change debate over the next 10 years - with those suffering a material loss likely to attempt to sue those reponsible for emitting greenhouse gases such as 
carbon dioxide + methane at some point in the future.
There are obvious difficulties associated with establishing the existence, extent + 
causes of 
recent climate change + even more with attributing 
blame but Earth-Info.Net still suspects that 
companies + countries in denial about global warming could eventually find themselves in a vulnerable legal position... 
In 2001, the 
IPCC's 
third climate change assessment report stated that it was "
likely" - meaning a 
better than a two in three chance - that human activities were forcing the global climate to warm up + 
Peter Roderick, a lawyer who works with 
Friends Of The Earth International, has recently said that "Civil courts usually require a 
51% proof of certainty, which is an interesting issue in terms of scientific levels of proof - and legal levels of proof."   
Visit the Met Office's 
Hadley Centre or the 
Tyndall Centre website for details on climate research + the 
Centre for International Environmental Law for a run down on the legal situation.
Also take a look at this 
graph of the global temperature record from 1860-2000!