Nevertheless, even if there is such decrease in the solar activity, there is a high confidence that the TSI RF variations will be much smaller in magnitude than the projected increased forcing due to GHG. – IPCC AR5 Chapter 8
Section 8.4.1 of the IPCC AR5 Report provides 2 pages of discussion on observations of solar irradiance. But they conclude that all this doesn’t matter for the climate. I agree that the TSI RF variations are much less than projected increased forcing due to the GHG. But the solar-climate connection is probably a lot more complex than this statement implies.
Climate Etc. has had 6 previous posts on the sun-climate connection [link]
Henrik Svensmark has an essay While the Sun Sleeps, that has been translated by WUWT. Excerpts:
The star that keeps us alive has, over the last few years, been almost free of sunspots, which are the usual signs of the Sun’s magnetic activity. Everything indicates that the Sun is going into some kind of hibernation, and the obvious question is what significance that has for us on Earth.
If you ask the Intergovernmental Panel on Climate Change (IPCC) which represents the current consensus on climate change, the answer is a reassuring “nothing”. But history and recent research suggest that is probably completely wrong. Why? Let’s take a closer look.
Solar activity has always varied. Around the year 1000, we had a period of very high solar activity, which coincided with the Medieval Warm Period. But after about 1300 solar activity declined and the world began to get colder. It was the beginning of the episode we now call the Little Ice Age.
It’s important to realise that the Little Ice Age was a global event. It ended in the late 19th Century and was followed by increasing solar activity. Over the past 50 years solar activity has been at its highest since the medieval warmth of 1000 years ago. But now it appears that the Sun has changed again, and is returning towards what solar scientists call a “grand minimum” such as we saw in the Little Ice Age.
The match between solar activity and climate through the ages is sometimes explained away as coincidence. Yet it turns out that, almost no matter when you look and not just in the last 1000 years, there is a link. Solar activity has repeatedly fluctuated between high and low during the past 10,000 years. In fact the Sun spent about 17 per cent of those 10,000 years in a sleeping mode, with a cooling Earth the result.
You may wonder why the international climate panel IPCC does not believe that the Sun’s changing activity affects the climate. The reason is that it considers only changes in solar radiation. That would be the simplest way for the Sun to change the climate – a bit like turning up and down the brightness of a light bulb.
Satellite measurements have shown that the variations of solar radiation are too small to explain climate change. But the panel has closed its eyes to another, much more powerful way for the Sun to affect Earth’s climate. In 1996 we discovered a surprising influence of the Sun – its impact on Earth’s cloud cover. High-energy accelerated particles coming from exploded stars, the cosmic rays, help to form clouds.
[C]limate scientists try to ignore this possibility. If the Sun provoked a significant part of warming in the 20th Century, then the contribution by CO2 must necessarily be smaller.
The outcome may be that the Sun itself will demonstrate its importance for climate and so challenge the theories of global warming. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable. A forecast saying it may be either warmer or colder for 50 years is not very useful, and science is not yet able to predict solar activity.
So in many ways we stand at a crossroads. The near future will be extremely interesting. I think it is important to accept that Nature pays no heed to what we humans think about it. Will the greenhouse theory survive a significant cooling of the Earth? Not in its current dominant form. Unfortunately, tomorrow’s climate challenges will be quite different from the greenhouse theory’s predictions. Perhaps it will become fashionable again to investigate the Sun’s impact on our climate.
Vahrenholt and Luning
The authors of The Neglected Sun, Fritz Vahrenholt and Sebastian Lüning, present a compelling series of reasons to say that not only is the belief in human-induced CO2 warming over-stated but that it ignores by far the most obvious influence of the Earth’s climate: the Sun.
The core argument is simple. The Sun may be a minor star in an insignificant part of our galaxy but in human terms it generates a staggering quantity of energy. Every second, it produces 620 million metric tons of hydrogen. It has been doing this for something like four billion years. It is estimated that it will continue to do so for a further 5.4 billion years.
That said, it is subject to a series of cycles: short, medium and longer term. These have clearly played the key role in the Earth’s climate. In the mid term, the most obvious are a series of ice ages, played out over thousands of years, briefly interrupted by warmer periods. The last five of these ice ages each lasted 100,000 years, the intervening warm periods about 10,000 years. Over the last 8,000 years or so, there has a period of unusually benign solar activity. Perhaps co-incidentally, this has precisely coordinated with what, historically, has been called the birth of human civilisation: settled communities, writing, agriculture, the domestication of animals.
In the shorter term still, every subsequent advance in human society has coincided with warmer periods, every reverse with cooler periods. Fast forward again and we find that since about 1850 a further period of modest warming has occurred. The IPCC contends that this warming, in stark contrast to all earlier periods of warming, can only be the consequence of increased CO2 emissions.
Never less than politely, Vahrenholt and Lüning tear this simplistic argument into minute shreds. They reserve their major criticisms for the debasement of the science. The West can clearly cite the scientific method as among its most obvious triumphs. Yet this painstakingly-won advantage is now being sacrificed, they contend, in the interests of activists, egos, political necessity and headlines. In short, the science has been corrupted in the interests of political expediency.
We can take some comfort from this. Truth has a way of winning, however painfully. Patently, Vahrenholt and Lüning have laid out what at the very minimum must be a serious case for calling into question the IPPC orthodoxy. To ignore their arguments can only be an act of deliberate obfuscation or deliberate ignorance.
There is a recent report, “The Effects of Solar Variability on Earth’s Climate,” available from the National Academies Press. A NASA press release entitled Solar Variability and Terrestrial Climate provides a good overview. The punchline is:
There is, however, a dawning realization among researchers that even these apparently tiny variations can have a significant effect on terrestrial climate. A new report issued by the National Research Council (NRC), “The Effects of Solar Variability on Earth’s Climate,” lays out some of the surprisingly complex ways that solar activity can make itself felt on our planet.
Note, this report was published early Jan 2013. Something else the IPCC ignored.
JC conclusion: What a relief that the IPCC consensus has decreed with high confidence that solar variations won’t influence the 21st century climate. For a minute there, after reading the NRC Report, Svensmark and Vahrenholt, I thought us scientists might have more work to do to figure out how the Earth’s climate system works.