Converging evidence on climate change

By Ken Perrott 31/01/2011

This graph thanks to Skeptical Science (Ten temperature records in a single graphic). As the web site says this graph of ten different temperature records provides “a vivid reminder that many independent lines of evidence all tell us the same thing.”

Pretty well underlines the fact that global temperature are rising. The Intergovernmental Panel on Climate Change (IPCC) describes this conclusion as unequivocal.

As for the cause – it’s worth recalling these figures from the last IPCC repport (I discussed these in Climate change is complex).

The figure below shows the results of simulations of global temperature from 1900 to 2005. Figure a included all the natural and anthropogenic influences.  The black line is the actual measured global temperature anomaly (obtained by subtracting the average temperature for 1901 to 1950).  The individual simulations are shown as thin yellow curves. The red line is the multi-model ensemble mean (see Figure 9.5 — AR4 WGI Chapter 9: Understanding and Attributing Climate Change).

Figure b is a similar plot using simulations which consider only the natural influences on climate. The individual simulations are shown as thin blue curves. The thick blue line is the multi-model ensemble mean.

So, climate scientist have considered both natural and anthropogenic influences. And they are unable to reproduce the global temperature changes since 1970 unless anthropogenic influences are included.

That is why the IPCC has concluded that there is a high probability (>90%) that human influences are contributing to the current observed global temperature increase.

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