Scientists from Livermore National Laboratory. E. Lawrence (LLNL) and five other organizations conducted a study that showed that human impact on the environment significantly affects the size of the seasonal temperature cycle in the lower atmosphere.
To demonstrate this, they used the so-called “fingerprint,” or human footprint method. This method aims to separate the human influence on the climate from the natural one. It relies on patterns of climate change that have averaged over many years or decades. In a new study, the team looked at seasonal patterns and found that human-induced warming significantly affected the seasonal temperature cycle.
The researchers focused on the troposphere, which extends up to 16 kilometers in the tropics and 13 kilometers at the poles. They analyzed the changes over time in the size of the seasonal tropospheric temperature cycle at different locations on the Earth's surface. This pattern provides information about temperature contrasts between the warmest and coldest months of the year.
Far from the softening effect of the oceans, the mid-latitude regions of the Northern Hemisphere continents have a large seasonal atmospheric temperature cycle with cold winters and hot summers. Satellite temperature data are consistent with models that show that this seasonal "heartbeat" is getting stronger as anthropogenic carbon dioxide emissions rise.
Observations and models also show small changes in the tropical seasonal temperature cycle and a decrease in the seasonal cycle in the Antarctic region. "Our results provide powerful new evidence of significant human influence on the Earth's climate," said climatologist and lead author Benjamin Sunter.
The research is published in the journal Science.