Clouds can amplify climate change but are not a root cause of it, a U.S. researcher says in a study that rebuts claims that clouds are prime climate suspects.

Texas A&M researcher Andrew Dressler says decades of data support the view that clouds are primarily acting as a so-called "feedback" that amplifies warming from normal climate cycles and human activity.

Cycles such as El Nino and La Nina, when waters in the central Pacific Ocean tend to get warmer or colder, have a huge impact on much of the world's weather systems for months or even years.

Texas is currently experiencing one of the worst droughts in the state's history, believed to be a direct result of La Nina conditions that have lingered in the Pacific Ocean for many months, a university release said Tuesday.

Clouds play a very small role in initiating these climate variations, Dressler said, and human activity remains a strong factor in climate warming.

"The bottom line is that clouds have not replaced humans as the cause of the recent warming the Earth is experiencing," Dressler said.

"Over a century, however, clouds can indeed play an important role amplifying climate change."