Scientists conclude we cause global warming

A team of international scientists has concludes there now is no doubt climatic changes are due to humans rather than any other natural factors.

Their report, published in the Proceedings of the National Academy of Sciences, builds on work previously done by scientists in the United States and presents a clear pattern of warming in parts of the atmosphere that is indicative of a human effect.

ABC News reports the only Australian researcher who was part of the team, Professor Tom Wigley of Adelaide University, says it analysed satellite temperature data over 34 years.

He said the team showed there was no other way to explain climatic changes at various atmospheric levels.

ABC News reports Professor Wigley said by looking at temperature changes across atmospheric layers from the Earth’s surface to about 20 kilometres skyward the results show clear characteristics of human interference.

“If the sun were the cause of the changes then one would see warming at the surface and in the lower atmosphere and in the upper atmosphere and in fact what we see is the opposite,” he said.

“We see warming at the surface and cooling in the upper atmosphere, so that immediately discounts the sun as a causal factor.

“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. What we have shown beyond a shadow of doubt is that the climate changes we are observing cannot be due to the sun or any other natural factors,” he told ABC News

Professor Wigley said the scientific team had concluded there was simply no other way to explain the changes that had occurred since 1979 when weather satellites were introduced.

ABC News reports the team found human influences, primarily greenhouse gases and related pollutants such as sulfur dioxide emissions and gases, had affected the atmospheric concentrations of ozone.

Professor Wigley said it was probably the most comprehensive study yet done to try to identify the human influence on climate.

“The main thing is that we can identify what is called a human fingerprint, or a distinctive pattern of change in the observational record, and that pattern is derived from climate modelling experiments,” he said.

“We look at patterns of change that can be attributed to other things, such as changing output of the sun for example, and we show that those cannot be identified in the observational record.

“We can see the human fingerprint, we can’t see the fingerprint of any other cause, and so it’s pretty obvious that the only explanation is there’s been a very distinctive human influence on the patterns of climate change.”

The scientists said more had been done to tackle ozone depletion than the effects of greenhouse gases.

“Greenhouses gases trap the warmth in, they allow radiation from the sun to penetrate to the lower layers of the atmosphere, but they don’t allow as much outgoing radiation and that’s what’s called the greenhouse effect,” Professor Wigley said.

Professor Wigley said the data relied on by scientists had a high degree of accuracy.

“The main workers are colleagues of mine that work in the Lawrence Livermore National Laboratory, which is part of the US Department of Energy in California.”