Monday, 8 November 2010

Global Warming is Driven By the Sun?

One of the most common myths the climate deniers promulgate, is that changes in our star's output is large, and large enough to explain rising temperatures.

They will make a big thing out of this sort of plot:

So you can see that indeed, the Total Solar Irradiance varies at earths orbit to a degree significant enough to measured.

There is ups and downs.

But the vertical scale is zoomed in between 1356 W/m/m and 1365 W/m/m

which is a zoomed in range of only 9W

But in actual fact, solar TSI varies normally according to the data plot between a minimum of 1360.5 to 1363.0 W/m/m; so Solar CYCLIC variation is worth about +/- 2.5 W/m/m which in percentage terms is is about 0.09% just by looking at this plot.

Climate Deniers, without any actual solar TSI data that extends back further, claim that there is actually a trend. A so called 'super cycle'. And indeed, from the data that is available, the IPCC factors that possibility into the Radiative Forcing Components summary by giving a trend range of solar irradiance between 0.06 and 0.3 W/m/m.

In their confusion, perhaps they jump on this low figure of best estimate: 0.12 W/m/m and see that it is at least an order of magnitude divergent from the +/- 2.5 W/m/m natural oscillation of TSI? Then they get confused between TREND and maximum observed CYCLIC variation. And whenever a denialist gets confused, they assume conspiracy.

The denialist, 'its the sun wot did it' hypothesis has some predictions associated with it. If changes to the climate are dominated by changes in the suns output, then there will be a different distribution of heat build up and fall off in the atmosphere.

The stratosphere temperatures should rise with the upper troposphere, if solar forcing was the primary forcing component...

...BUT IT ISN'T:  Weather balloons (not affected by the ridiculous attacks of the reputation of weather stations (they put their weather stations next to a chimney type of argument)) show falling lower stratospheric temperatures with rising upper troposphere. This observation destroys the solar forcing hypothesis whilst backing CO2 Forced explanation.

So although solar forcing is a perfectly reasonable counter hypothesis, a falsifiable one, it has been shown to be false, as an explanation.

met office:

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