The Sun (4):
This is the fourth of a series on the Sun in the Earth-Sun climate system. The first three entries are linked at the end. This one starts with some news sent to me by Judith Lean. There’s a sunspot! There’s a news story at Spaceweather.com
. And here is a picture from that website credited to the SOHO/MDI
instrument. (I’ve also put a couple of news and information links at the end.)
Figure 1: This figure shows in the circle a sunspot. The minimum of sunspots at the end of the last solar cycle (#23) has extended for a long time. While long, the minimum is still not outside of the natural variability of the observed record (1 standard deviation). The polarity of this new sunspot shows that it is the beginning of Solar Cycle 24. Picture is credited to Michelson Doppler Imager
on the Solar and Heliospheric Observatory
As noted in the figure caption and the article by Irene Klotz, Sunspot Record Reveals Little to Space Weather Watchers
from the American Geophysical Union’s Space Weather Website
, the length of this sunspot minimum is still within the statistical norm of previous observations. Like the Earth, we have far more observations of the Sun than in the past. The climate problem brings extensive scrutiny to these observations, and hence increases our sensitivity to information being collected. This new sunspot is, seemingly, the start of the next solar cycle, # 24.
Let me summarize the points from the last three blogs. There is a measurable solar signal that we can measure in the Earth’s climate. There is about a 0.1 degree centigrade signal that can be measured over the, approximately, 11 year sunspot cycle. This variability is included in models, but models underestimate the variability. That is, the observed variability is greater than the modeled variability. This model shortcoming is an important aspect of modeling to address. Currently models do not seem able to communicate changes high in the atmosphere to the Earth’s surface. There needs to be some mechanism in the atmosphere that modulates or amplifies this signal. This is likely to be related to the state of the atmosphere, meaning persistent weather patterns. This potential relation to the atmosphere is postulated because if the solar cycle is investigated taking into account, for example, the phase of the Northern Atlantic Oscillation
, the clarity of the solar signal is enhanced.
While the weakness of the modeled versus observed solar cycle is a challenge that climate modelers still need to address, in general, it is possible to evaluate what this model weakness might mean to observed and predicted climate change. For example, we have the observational information of the sun and the climate and the observed contribution of solar variability to the Earth’s warming is more than 10 times smaller than that due to greenhouse gases. And, this relative size of solar-related warming to the greenhouse gas warming is getting smaller in recent years – explicitly, the observed warming is dominated by the greenhouse gas effect, and this domination is getting larger.
In the last blog, The Sun (3)
, I tried to set the foundation for thinking about the warming due to the greenhouse effect by following a ray of sunlight through the atmosphere. Ultimately, an enormous component of the radiative heating that keeps the Earth’s surface warm are due to the greenhouse gases in the atmosphere --- more that twice the heating than comes directly from the Sun. Therefore, it is relatively simple to both attribute and understand the warming at the Earth’s surface to the systematic increase of greenhouse gases.
The data show the greenhouse gas warming to be much larger than the warming associated with changes in the Sun. Since the models underestimate the solar signal, the likelihood of the model obscuring some fundamental, underlying mechanism that is fooling us about greenhouse gas warming is very low. There are many ways to add strength to this conclusion; I remind you of the series of blogs on attribution
The plan is that the next blog will be the last in the series on the Sun-Earth climate connection. I want to point out an interesting and well written on line document The Sun and the Earth’s Climate
by Joanna Haigh
. The next blog will talk about solar variability in the projections of the future climate.
Postscript some news items:
Jeff Masters recently did an update of the 2008 sea ice. It was very low again. Here is a link
Here is a website with some pictures important to global warming. It’s a wiki and has community participation. Global Warming Art
. Here are thumbnails of all the figures in their archive
Here is a website that documents the societal debate about global warming. Climate Debate Daily
. Thanks to reader Aaron for pointing this one out.
Blogs on the Sun. The Sun (1) The Sun (2) The Sun (3)
Blogs on radiative balance Absorbing Reflections Ice Water Clouds Cool and Warm Aerosols Cool and Warm