UN: Sun plays significant role in global warming.

Since the PETM (a climate we'd never want to repeat!) ~55 million years ago, Earth has generally gotten colder. There is no evidence that solar output has generally decreased over that time (assuming y'all know about the paleo isotopic proxies). At the same time, (other) paleo isotopic proxies for atmospheric CO2 suggest that it has generally decreased over that time. There are geological and biological reasons for that. Even in the absence of knowledge that CO2 absorbs IR, one would be inclined to consider the T/CO2 correlation.

A wide range of climates happened during that time, without humans messing with the carbon cycle. But now we are sending new CO2 to the atmosphere 100 times faster than volcanoes that used to dominate the 'new' supply side. As we know that CO2 absorbs IR, and we know that generally that solar output will increase, no one should be surprised that this is a topic of great interest.

It can be considered at a range of time scales, but that of most interest for us (I'd say) is decades to century. At that scale, marine redistribution of heat and its trapping of CO2 seems pretty lively, and I'm not sure that it is well captured by the current coupled models. But, maybe that's just me.

Invoking unnecessary confusion about time scales probably won't help, and it seems to me that both Al Gore and our own mojo do so (but with different goals ).

The current solar cycle is relatively weak. But to suppose that it will go next to another Maunder minimum requires that you put all your money on Penn & Livingston, and set aside the recent CMEs. El Sol is not dead!

But, OK, let's just suppose that we could get 2 (or more) weak solar cycles back to back. This happened a century ago, at about 300 ppm CO2, and Earth did not ice over. Now, with 400 ppm CO2, will we? Wanna bet?

I don't think that the current models are good enough to predict whether another solar Maunder minimum would ice the Earth, mostly because of that ocean thing. But (a) hopefully invoking a future extended solar minimum and (b) hopefully presuming that CO2 doesn't absorb IR, well, that doesn't quite cut it. Our prosperity depends on climate being 'just so' as it has been (more or less) for about 50 centuries.

Even more so now, because we are so many more and need rain much more for agriculture and thermal energy production. In these ways, we are narrowing the range of acceptable climates.

We could continue to increase the IR absorption by fossil-C burn, and hope that the sun will get the memo and benevolently tune down just the right amount so that we continue to get great climates.

Yeah, we could.

 

I absolutely agree here, but I would say the transfer function of solar radiation and of methane because of various feedback's should be at least 100 years if properly modeled. I have done heat transfer models as parts of NSF grants but nothing in climate change. Since we have only been accurately recording solar radiation for about 50 years there is much uncertainty here and in the proxies of sun spots. That may help explain my hope that lower radiation in the current solar cycle may help remove some of the uncertainty. The changes will help us gauge both the relation of sun spots to solar radiation and the heat transfer function.

Hansen has hypothesized that particulates, and gasses like SO2 and NOx have been higher sensitivities to explain why his low solar sensitivity models may have been off. Future data should help support or contradict this hypothesis also.

+1

Absolutely the boundary conditions for the little ice age were quite different, and there is great uncertainty on the solar cycle. That places anouther maunder minimum at quite a low probability, and the changes that it would cause another little ice age very low.

I have seen nothing scholarly that would predict a little ice age under that scenario. What I see is some raw speculation that appears to me as unlikely as a 6 meter sea level rise by 2100. What two weak solar cycles would do would be to slow the warming, it would not ice the earth over. To do that would take many more weak solar cycles.

 

Here is the big question, and one that I don't think you can possibly address if you only look at the last 50 years. How long does it take for the heat from solar radiation to fully adjust temperatures. If we assume it only takes a few years all of the models of ice ages are wrong. This is why paleo climate proxies are important.

If you end up getting the temperatures wrong by a large factor over say 200 years, there is no way to validate a model. It is difficult to separate natural from man made. We need a good model of how high the temperature would be today if man did the same level of paving the planet and deforestation and farming but did not release fossil fuel methane or co2 or particulates, NOx, etc. It would almost certainly been higher today than 1880, but how much? Then we can back out the additional fossil fuel burned products.

 

Nova just had a 2 hr episode on the Earths' weather and how it is affected by our star. Satellites (Goes, etc) are compiling interesting data from weather systems around the Earth. Newer satellites are seeing interesting data being viewed in infrared to uttraviolet spectrum as a start.
this Nova espisode was on public service tv. Season 40, episode 6.

Catch it if you can.

DBCassidy

 

Given the amount of heat required to raise the emperor urge of water, and given the vast volume of liquid volume (on the surface) on the planet, I would posit that the rate of global warming from addition of GHG is quite small. With that in mind, the amount of warming we have seen in a relatively short time is even more alarming.

It has been suggested that we are seeing the effect on current climate from GHG emitted decades ago (as concentrations have been growing for ~200 years!) it is only rational to assume that the future is more likely to get warmer, faster as a result of the emissions of more recent times.

Add in emissions from melting permafrost, sea water methane, not to mention decreased albedo of snow and ice covered areas, less thermal mass encased in ice, and the potential is bleak.

Icarus