In a number of portions of the report, graphs appear trying to show climate variations in absurdly narrow time windows. This helps the authors either a) blame long-term climate trends on recent manmade actions or b) convert natural variation on decadal cycles into a constant one-way trend. In a previous post I showed an example, with glaciers, of the former. In this post I want to discuss the latter.
Remember that the report leaps out of the starting gate by making the amazingly unequivocal statement:
1. Global warming is unequivocal and primarily human-induced. Global temperature has increased over the past 50 years. This observed increase is due primarily to human induced emissions of heat-trapping gases.
To make this statement, they must dispose of other possible causes, with variations in the sun being the most obvious. Here is the chart they use on page 20:
Wow, this one is even shorter than the glacier chart. I suppose they can argue that it is necessarily so, as they only have satellite data since 1978. But there are other sources of data prior to 1978 they could have used**.
I will show the longer view of solar activity in a minute, but let’s take a minute to think about the report’s logic. The chart tries to say that the lack of a trend in the rate of solar energy reaching Earth is not consistent with rising temperatures. They are saying – See everyone, flat solar output, rising temperatures. There can’t be a relationship.
Really? Did any of these guys take basic thermodynamics? Let’s consider a simple example from everyone’s home — a pot on a stove. The stove is on low, and the water has reached an equilibrium temperature, well below boiling. Now we turn the stove up — what happens?
In this chart, the red is the stove setting, and we see it go from low to high. Prior to the change in stove setting, the water temperature in the pot, shown in blue, was stable. After the change in burner setting, the water temperature begins to increase over time.
If we were to truncate this chart, so we only saw the far right side, as the climate report has done with the sun chart, we would see this:
Doesn’t this look just a little like the solar chart in the report? The fact is that the chart from the report is entirely consistent both with a model where the sun is causing most of the warming and one where it is not. The key is whether the level of the sun’s output from 1987 to present is a new, higher plateau that is driving temperature increases over time (like the higher burner setting) or whether the sun’s output recently is consistent with, and no higher than, its level over the last 100 years. What we want to look for, in seeking the impact of the sun, is a step-change in output near when temperature increases of the last 50 years began.
Does such a step-change exist? Yes. One way to look at the sun’s output is to use sunspots as a proxy for output – the more spots in a given 11 year cycle, the greater the sun’s activity and likely output. Here is what we see for this metric:
And here is the chart for total solar irradiance (sent to me, ironically, by someone trying to disprove the influence of the sun).
Clearly the sun’s activity and output experienced an upwards step-change around 1950. The average monthly sunspots in the second half of the century were, for example, 50% higher than in the first half of the century.
The real question, of course, is whether these changes result in large or small rates of temperature increase. And that is still open for debate, with issues like cloud formation thrown in for complexity. But it is totally disingenuous, and counts on readers to be scientifically illiterate, to propose that the chart in the report “proves” that the sun is not driving temperature changes.
**By this logic, they should only have temperature data since 1978 for the same reason, though by one of those ironies I am starting to find frequent in this report, all the charts, including this one, use flawed surface temperature records rather than satellite data. Why didn’t they use satellite data for the temperature as well as the solar output for this chart? Probably because the satellite data does not include upward biases and thus shows less warming. Having four or five major temperature indices to choose from, the team writing this paper chose the one that gives the highest modern warming number.