Royal Society & NAS: Sun’s variations have played very little role in climate change

The Royal Society, in collaboration with the NAS has published a long document about the evidence and causes of climate change. Section’s 4 & 5 deal with the Sun. Count the misleading statements and omissions:

4. What role has the Sun played in climate change in recent decades?

The Sun provides the primary source of energy driving Earth’s climate system, but its variations have played very little role in the climate changes observed in recent decades. Direct satellite measurements since the late 1970s show no net increase in the Sun’s output, while at the same time global surface temperatures have increased (see Figure 2).

Figure 2. Measurements of the Sun’s energy incident on Earth show no net increase in solar forcing during the past 30 years, and therefore this cannot be responsible for warming during that period. The data show only small periodic amplitude variations associated with the Sun’s 11-year cycle. Figure by Keith Shine. Source: TSI data from Physikalisch-Meteorologisches Observatorium Davos, Switzerland, adjusted down by 4.46 W m-2 to agree with the 2008 solar minimum data from Kopp and Lean, 2011; temperature data from the HadCRUT4 dataset, UK Met Office, Hadley Centre (larger version)

For earlier periods, solar changes are less certain because they are inferred from indirect sources — including the number of sunspots and the abundance of certain forms (isotopes) of carbon or beryllium atoms, whose production rates in Earth’s atmosphere are influenced by variations in the Sun. There is evidence that the 11 year solar cycle, during which the Sun’s energy output varies by roughly 0.1%, can influence ozone concentrations, temperatures, and winds in the stratosphere (the layer in the atmosphere above the troposphere, typically from 12 to 50 km, depending on latitude and season). These stratospheric changes may have a small effect on surface climate over the 11 year cycle. However, the available evidence does not indicate pronounced long-term changes in the Sun’s output over the past century, during which time human-induced increases in CO2 concentrations have been the dominant influence on the long-term global surface temperature increase. Further evidence that current warming is not a result of solar changes can be found in the temperature trends at different altitudes in the atmosphere (see Question 5).

5. What do changes in the vertical structure of atmospheric temperature – from the surface up to the stratosphere – tell us about the causes of recent climate change?

The observed warming in the lower atmosphere and cooling in the upper atmosphere provide us with key insights into the underlying causes of climate change and reveal that natural factors alone cannot explain the observed changes.

In the early 1960s, results from mathematical/physical models of the climate system first showed that human-induced increases in CO2 would be expected to lead to gradual warming of the lower atmosphere (the troposphere) and cooling of higher levels of the atmosphere (the stratosphere). In contrast, increases in the Sun’s output would warm both the troposphere and the full vertical extent of the stratosphere. At that time, there was insufficient observational data to test this prediction, but temperature measurements from weather balloons and satellites have since confirmed these early forecasts. It is now known that the observed pattern of tropospheric warming and stratospheric cooling over the past 30 to 40 years is broadly consistent with computer model simulations that include increases in CO2 and decreases in stratospheric ozone, each caused by human activities. The observed pattern is not consistent with purely natural changes in the Sun’s energy output, volcanic activity, or natural climate variations such as El Niño and La Niña.

Despite this agreement between the global-scale patterns of modelled and observed atmospheric temperature change, there are still some differences. The most noticeable differences are in the tropical troposphere, where models currently show more warming than has been observed, and in the Arctic, where the observed warming of the troposphere is greater than in most models.

_________________________________

So, we’ll start at the beginning. Here’s the first misleading statement:

“Direct satellite measurements since the late 1970s show no net increase in the Sun’s output”.

That’s because since 2004, solar activity level has slumped to a centennial low. However according to the direct measurements, solar activity was rising to that date, as shown in Scafetta and Willson’s recent paper. The PMOD model is wrong.

Next we have Fig2. With a little use of freely available plotting facilities (thanks Paul) we can see that solar activity strongly affects global surface temperature on the decadal timescale.

The next falsehood lies in this statement:

“Sun’s energy incident on Earth show no net increase in solar forcing during the past 30 years, and therefore this cannot be responsible for warming during that period.”

Utter bollocks. The ocean is 5km deep and water has a high heat capacity. The later C20th solar activity was much higher than the long term average all the way from 1936 to 2004. The ocean would have carried on warming even if the peak amplitudes of the solar cycles were descending gently from the historic record high of 1958. Which incompetent wrote this nonsense?

Onto the next:

“TSI data from Physikalisch-Meteorologisches Observatorium Davos, Switzerland, adjusted down by 4.46 W m-2 to agree with the 2008 solar minimum data from Kopp and Lean,”

How convenient. Adjusted to make TSI flat. At least they’ve stopped using the aperture reflections excuse and admit it’s an arbitrary decision.

“the available evidence does not indicate pronounced long-term changes in the Sun’s output over the past century”

Taking the 60 year oceanic oscillation into account, sea surface temperature has only increased by 0.3% or so over the last century, changes in the Sun wouldn’t have to be “pronounced” to explain most of global warming.

I’ll leave the rest of section 5 to our readers to criticise. Stephen Wilde and ren probably have something to say about it.