Climate Change having "Natural Causes" is Far More Alarming

It strikes me that the set of climate deniers who say "yes the earth is warming, but it is natural causes not human behaviour" think somehow this is a sufficient and comforting explantion.  Actually it would be a far far more alarming explantion for the phenomena if one considers it rationally:

• First off it means the world's collected climate experts know absolutely nothing about what could actually be causing this, since they have looked into every possible natural cause they can think of, and found no evidence to support any of them as driving the observed climate change.  No one should ever think smugly that science knows everything there is to know about something, but the idea that a major climate driver could elude human understanding means we are missing something huge, and it's hard to view that with any kind of aplomb.  This kind of scientific gap in our understanding of the world would almost certainly have to be much larger than climatology, it would likely be some form of physics or chemistry of which we have not even a theory to account for.  What mystery energy source could be injecting or retaining additional energy into the climate? 
• Secondly and tied to the first, if we have no idea what is warming the planet, it means we have no possible way of knowing how bad this problem will get, how fast, and whether there is any possible way to stop it.  At least we know if we are causing global warming with our emissions, we can stop adding to the problem by reducing emissions, and maybe even solve the problem if we can find a way to remove carbon from the atmosphere (or in extremis, treat the more catastrophic symptoms through some kind of risky geoengineering scheme).  Will it warm 1 degree per decade?  10 degrees?  Maybe the Earth will actually end up like Venus, completely uninhabitable. Even geoengineer schemes, as suspect as they already are would be doubly dubious in an environment where we didn't actually understand the causes of climate change. 
• Last, and I've made this point before, but a naturally warming planet is still something we need to deal with and prepare for.  Sea walls don't build themselves.  Coastal settlements still need to move inland.  Agricultural land suitable for growing food under new climate norms will still need to be located, and prepared for growing food, water supplies for areas destined to become especially arid must be located or those communities moved.  All of this is expensive, and you either invest up front and ameliorate some of the effects, or you pay through the nose to recover from various disasters. 

None of this should reflect any doubt on my part about the veracity of the science telling us that human greenhouse gas emissions are the overwhelming cause of global warming.  But it is more a statement on the irrationality of this particular (and in my experience, now most common) denialist position.  If you really do believe "natural causes" are the reason for warming you should be a major advocate for huge additional resources for science to get to the bottom of the actual causal mechanisms, and for money being spent to prepare for the predictable effects of such warming.

And no, you can't rely on some airy fairy idea of "natural cycles" - wheels turn until they break.  Mars was once warm enough to have liquid water on it.  Something about its climate cycle 'broke' and now it is far too cold for that (and its atmosphere too thin, as well).  The Earth was not always a place that life as we know it could survive.  It had vastly different atmospheric compositions, temperature ranges and so forth.  Think we could survive an atmosphere that was half as thick?  Or twice as thick?  Or with half the oxygen?  Or twice as much?  

You needn't be surprised that I have yet to see any climate change deniers of this sort make such calls.  Somehow the mystery source of knowledge they have (I believe they sit on it) also tells them that the warming will be modest and slow and adaptation is no problem.  But if you don't actually know what is causing the warming, you can't really have that assurance. The past 10,000 years or so have seen a climate pretty well suited to humans.  There is no reason to think that must continue.  A giant asteroid on course to hit earth would be "natural" too, but in no way would that obliviate any need to do anything about the problem.