Australia’s "60 Minutes" has broadcast an item called "Crunch Time" which made much of the opinions of David Evans, a computer programmer with a PhD in electrical engineering who once worked on a mathematical modeling program for the Australian Greenhouse Office. Dr Evans put two arguments to support his view that global warming is not caused by carbon emissions. Dr Evans first point was that, although carbon emissions have continued to increase, global temperatures have not increased for the last eight years. Here is the graph of global temperatures from  the UK Met. Office’s Hadley Centre. It’s difficult to see Dr Evan’s evidence that temperatures have stopped going up.

Dr Evan’s other argument is that there is no "greenhouse signature". The signature that he says he has been searching for is greater warming of the troposphere over the tropics. Indeed, he said that if there was such a signature, he would accept that carbon emissions were causing global warming. Well. here is his "signature"

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What we’re looking for is the black line indicating high temperature in the upper middle of the second graph on the top row. Unfortunately, we can’t really demand that Dr Evans change his opinion of the basis of these graphs because he has been searching for the wrong thing. These tropical temperature graphs show that global warming is happening but tell us nothing about its cause. As we all know by now, greenhouse gases reflect heat back to the earth. This means that less heat gets through to the stratosphere above the greenhouse layer. So, the real signature of greenhouse gases is cooling in the stratosphere while the lower atmosphere is warming – which is exactly what we find:

The first graph shows decreasing temperatures in the stratosphere. The others show less decrease at lower altitudes. The "60 Minutes" programme didn’t raise any real questions about global warming – the only real question is why did they broadcast such a one-sided view?