Your first and third arguments hold the most merit. It's always interesting to consider the existence of aliens, and the sheer size of the known universe provides nearly endless possibilities.
Some food for thought:
Humans are weak physically, and not very resilient to weather. So, of course it is true that historical civilizations on Earth have eventually collapsed (when weather conditions changed, resources dried up, or conquerors arrived). But what is to say that an alien race would be remotely similar to us biologically? That is a heck of a stretch based on the [nothingness] we currently know about alien life.
Also, you should check into Co2 a bit more. It follows a logarithmic curve, where each additional molecule contributes to less of a warming effect than the previous. Additionally, increased Co2 in the atmosphere significantly increases the rate at which plant life grows on this planet. The catastrophic views about our climate are blown way out of proportion - as they have been for the last twenty years. There have been dozens of climate models predicting catastrophe in that time - and guess how many have come close to getting it right as time went by? Zero. I know this wasn't a climate post, so if you disagree, no worries. Just something that curious minds in the past have found intriguing; thought I'd share.
Thank you for explaining how Co2 works, but global warming could also happen even if each molecule does less than the previous, because our planet can't absorb Co2 at enough speed to counter it's effects.
Global warming may take more time than people say but gradually it will be happening in the future
Well, yes and no. Logarithmic curves essentially hit a point where they stop having a meaningful increase for each additional input, and we're nearing that point. Meaning that even if the levels continue to rise, they have an irrelevant impact.
As a corollary, are you familiar with the fertilization effect of Co2? Additional Co2 in the atmosphere causes a significant (both literal and statistical) increase in the growth of plants - meaning that the earth has a growing capacity to remove Co2 from the atmosphere.
I don't deny global warming, but the question we really need to understand and answer is: Is it bad? As I mentioned, many catastrophists have said it would be terrible, yet none of the predictions have ever been remotely accurate. Climate related deaths are dropping as the temperature changes and our technology improves.
Humans fundamentally change their environment. It's how we survive. We adapt, and every indication leads to the notion that we will continue to do so, even as our planet warms (or fluctuates, as it has always done).
Thanks for responding in a positive way!
What about other animals, they don't improve their technollogy so every time there are less species in the earth, maybe humans can survive but I thing we should take care of the other live beings.
Maybe plants absorb Co2 faster when there's more of it, but isn't there a limit to?
Also in order to absorb more, plants produce less protein and zinc so we would need some other way to supply humans from these essential things.
In conclusion global warming will be bad for earth's biodiversity.
If i don't reply to this in the next few days leave me a comment on one of my posts - id like to respondto you in some detail but I'm embarking on a 4-week, 5 state trip in the morning and things are crazy right now.
Okay, just talk when you have time ;)