Climate scientists report strong evidence for human global warming

International climate scientists, led by the Lawrence Livermore National Laboratory (LLNL) in the United States, have reported strong evidence of the human influence on climate change.

In a comprehensive study published in the Proceedings of the National Academy of Sciences of the USA (PNAS), the researchers analysed satellite temperature data over the past 34 years, whose measurements revealed “multidecadal tropospheric warming and stratospheric cooling, punctuated by short-term volcanic signals of reverse sign”, they said.

They then compared these data with results from several climate models driven by human-caused influences, focusing on the vertical structure of atmospheric temperature change (from the troposphere or lower levels of the atmosphere through to the stratosphere or upper reaches of the atmosphere).

“We show that a human-caused latitude/altitude pattern of atmospheric temperature change can be identified with high statistical confidence in satellite data,” the researchers said.

The study built on a previous LLNL study from 1996. The new study adds an extra 20 years of data - and evidence of human climate change - to the earlier work, according to researcher Professor Tom Wigley from the University of Adelaide’s Environment Institute.

While the original study was the first published work to clearly identify the human fingerprint in observed temperature changes, Professor Wigley says the new study has been able to better define the human signal in atmospheric temperature change.

“One of the standard sceptic ‘arguments’ is that all the observed changes are caused by natural variability, and often supposed to be due to solar activity,” he said.

But the researchers identified a clear pattern of warming temperatures in the troposphere and cooling temperatures in the stratosphere, and they claim, “Internal and total natural variability (as simulated by state-of-the-art models) cannot produce sustained global-scale tropospheric warming and stratospheric cooling.”

“There is simply no other way to explain the changes that have occurred since 1979 … other than as a result of human influences - primarily greenhouse gases and related pollutants like sulfur dioxide emissions and gases that affect the atmospheric concentrations of ozone,” Professor Wigley concluded.

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