"Our results suggest that attribution studies with the changing seasonal cycle provide powerful and novel evidence for a significant human effect on Earth's climate," Benjamin Santer, LLNL climate scientist and lead author on the new work, said in a statement.  

Climate fingerprint research, which originated in the 1970's, studies climate patterns to find the source of large climate changes. It takes into account natural factors that contribute to climate like ocean heat, the water cycle, circulation in the atmosphere, sea ice, and extreme natural events, according to the statement. In this study, researchers studied model climate simulations driven by historical changes in human behavior.  

The team found a highly significant "pattern match" between seasonal temperature trends and the human influence, or "fingerprint," on the troposphere, according to the statement. This shows that observed changes in our atmosphere and seasonal tropospheric temperature cycles are most likely caused by human action, the study said.

This is the first formal fingerprint study that has ever been conducted with the changing seasonal tropospheric temperature cycle, according to the statement.

This work was published July 20 in the journal Science.