A friendly discussion about the inlfuence of the sun on climate....

DPinBucks

Thanks for that.

I purposely didn't mention specific solar cycles, because there is no reason to single out any of them as having more or less influence on climate than any other. This is especially true of any, such as the 11 year sunspot cycle, with periods of a few 10s of years or fewer. They influence the weather (eg El Niño and La Niña), but don't affect the climate, because that is established over longer periods. There are longer solar cycles which do cause climate shift, but of all the factors I list above, the Sun is by far the most predictable, and nearly the most stable (only the Earth's magnetic field and meteors have less effect over the very long term). It must be so, or we wouldn't be here.

In climate modelling nothing can be ignored, but the Sun is certainly no more than just another player, and a minor one at that.

Miyazaki

Time to close the thread then.

NikB

The sun may be stable but our orbit around it varies as does the angle of obliquity which works on a 24000 year cycle. This may have a significant impact on climate. Another influence which I suspect may be very difficult to measure is the region of space we are in. In recent times there has been more activity at the sun's heliopause which has suggested we've entered a higher energy region of space.

DPinBucks

Possibly. 24,000 years is certainly into climate territory.OK, add
Cosmic Neighbourhoodto my list above, if you want. Mind you, I'm not at all sure what a 'higher energy region of space' might mean. What energy? Where from?

NikB

Cosmic radiation I believe, it's a while since I read it so I can't remember for certain. The way I understand it is that the solar system moves above, into and below the galactic plane (y axis) and also through the arms (x axis) and presumably the particle density of those regions has an influence on radiation levels.

johntheexpat

That's all very well, but surely the Global warming 'problem' is lot more urgent?  If we start talking about the vagaries of 24,000 year cycles, we take our eye off the ball concerning the relevant MMGW problem.  For the sake of the next hundred years or so when MMGW and CC are supposed to kick off in a big way, surely the Sun and our Cosmic Neighbourhood can be taken as reasonably stable elements in the equation.

Its quite possible the proximity is relevant to climate change when measured over tens of millenia.  But over the next 100 years?

DPinBucks

As a mechanism, it sounds plausible, but when you slot figures in you start to wonder a bit.

I can't find out the inclination of the sun's orbit to the galactic plane, but let's say it's 30deg (it's almost certainly much less than this). Its orbital velocity is about 220km/sec, so along the z-axis it will be 220 x cos60 = 110km/sec. It does wobble a bit as well, so it's not as simple as all that.

Any variation in cosmic ray background would surely be spread over distances measured in light years. At 110km/sec, it will take about 1,400 years to travel 1 light year, and the sun will cross the galactic plane every 115 million years or so.

It seems to me that, even if the effect is real, it is too infrequent to have any significant effect on climate, and even if did its effects would take too long to be noticeable over any period of less than a thousand years or so.

Still, it's plausible, so let's leave it on the list.

DPinBucks

I completely agree; the Sun is largely irrelevant. But remember the question was about random effects. I was listing all those I could think of, to see how random they are, and to some extent how significant. Although far and away the most urgent is fossil fuel consumption, I would not want to be accused of selectivity.

And I thought we were trying to steer clear of MMGW in this thread? If we don't, it's going to get closed again.

GasDad

Can we add plate tectonics to the list ?

BISHI

Other things to consider
- Shift of agriculture from arable to lifestock in the developing world to facillitate the increasing demand for meat, resulting in less vegetation to act as a carbon sink and massively increased production of methane.
- Increased demand for petrol in the same developing areas of the world
- Increasing number of coal fired power stations particularly in China.
-Perhaps the most important factor is sea pollution which kills the plankton responsible for the greatest volume of carbon absorbtion on the planet.

I am also wondering if the polar wobble may affect the amount of solar radiation absorbed by different areas on the planet surface, we are overdue a flip in polarity and that must have an effect on the consistency of the magnetic fields around the planet deflecting the solar wind...