The proliferation of jellyfish in the oceans may be a fairly bad sign, although to what extent the problem is climate change vs all the other bad things humans do to the oceans is up for grabs. The science--like the science of climate itself--is not even remotely close to "settled", but there is cause for concern:
http://www.wunderground.com/news/oceans-may-be-primed-jellyf...
It's also worth remembering that the Earth's climate over most of the 20th century was amazingly stable by historical norms. Year-to-year variation was fantastically small compared to the kind of thing seen pretty routinely in the past few thousand years. There were no multi-decadal mega-droughts, no dramatic swings in northern hemisphere temperatures of the kind seen in the Little Ice Age or the Medieval Warm Period, and so on.
It follows from this that even a return to natural variability is going to be challenging for us, and it's unlikely that the 1.6 W/m^2 that anthopogenic greenhouse gasses are adding to the mix is going to make things any calmer. Adding energy to chaotic systems rarely makes them more stable, and while the detailed consequences of the additional energy are unclear (despite what the "science is settled" folks claim) there is very little doubt that we are adding 1 - 2 W/m^2 to the Earth's energy budget.
That said, here's a relatively agnostic argument for carbon taxes, which the data show are pretty effective at curtailing greenhouse emissions: most carbon tax schemes are designed such that the revenue they generate allows governments to lower corporate taxes and person income taxes. Now, unless you're a wild-eyed socialist revolutionary who hates wealth and capitalism, you're likely in favour of lower corporate taxes and personal income taxes. I know I am. I would far rather have a tax on something bad (dumping waste into the atmospheric commons) than something good (income!) So I think there's an argument to be made for carbon taxes that even the most ardent capitalist can like, if not love.