The argument here is that global warming is caused by the presence of methane in the dams. The larger the dam, the more methane that is collected in the dam. The growing amount of rotted organic material that is present in the dam helps to generate the methane that traps more heat within it than carbon dioxide. The belief here is that the bigger the dam, the more methane is generated, and the more heat is trapped and then eventually released into the atmosphere. The dam building industrial complex is not comfortable with this information being released because building dams is a very profitable business. Yet, it is in this light where the cause for concern arises. It is for this reason that climate change advocates believe that there has to be some level of remedy in the policy making arena to address this concern:
"There is now more than enough evidence to show that large dams are a major source of climate-changing pollution," says Patrick McCully, Executive Director of International Rivers. "Climate policy makers must address this issue."
The presence of methane is the root of the argument behind how dams can contribute to the issue of global warming.