Some things destabilize--others stabilize. There's no scientific evidence to back the claim that cold water melt screws up ocean currents (ocean currents are propelled by warm water--melting ice adds cold water, and then only to spots of water that are already cold--which doesn't destabilize the current, it reinforces it). Deserts shrink. Farmland becomes more productive.
Good god, I think I literally twitched.
Let's see. Ocean currents are propelled by the interchange of cold and warm water, not by either warm or cold water alone. Areas in which cold water sinks towards the ocean bottom and warm water rises to the top are the pulleys which make our ocean currents trundle along.
Cold water from, say, the Greenland glacier melting, would flood the region of the Labrador current, which is at present not particularly strong, and sinks underneath the Gulf Stream (which, I trust, you will not dispute is pretty important to the regulation of Western European climate). This meltwater would be primarily
fresh water, which is, in fact, scientifically proven to be less dense than sea water of a comparable temperature, and significantly so. Thus, this water will tend to ride higher than it should, and will screw up the Gulf Stream.
Now. Some deserts will shrink, eventually, and some will grow. And the people living on the edge of those deserts which are growing will be
displaced. These people will
move elsewhere. This will likely cause them to
move towards people whose deserts are shrinking. Oh nuts, suddenly you have widespread population movement, which will probably lead to armed conflict.
Will farmland grow? Overall? Who knows, the models are conflicting. But again, you'll have widespread population movement, and on top of that, glaciers melting
generally means you cannot use the water in them later, so certain rivers which are glacially fed (read: Indus, Ganges, Brahmaputra) will very suddenly
not flow as heavily. And an area with
hundreds of millions of people will have less irrigation water.
And so on.
Stop trying to paint a rosy picture. Significant global temperature changes are not going to do nothing in the net -- they're going to create very large problems with complicated solutions where solutions exist at all.
As always, you're only pointing out those things that go wrong and ignoring those things that go right.
"As always." I, uh, would question how well you know me, but...
Yes, certain areas receive more rainfall. Certain areas will also become beachfront property. Also, in a thousand years, the Earth will end up better off, biomass wise, for an increase in temperature.
Does that mean it's going right? Depends on your point of view. The change is usually pretty nasty.
Yes they do. What is a greenhouse gas? It's an insulator. It reflects heat back the way it came. Insulators reduce temperature gradients. Example: the insulation on your house. What does that do? It keeps the house warm in winter and cool in summer. More greenhouse gases make the planet warmer and eliminate radical temperature changes. They're the only reason the Earth isn't boiling hot on the day side and a popsicle on the night side--as Mercury is.
*blinks*
Yes, greenhouse gasses are an insulator. Between the Earth's surface and the vacuum of outer space.

They do little to insulate between different regions of the Earth's surface. The difference in temperatures is not caused by some sort of weird distribution of greenhouse gasses, as you seem to be implying. The difference in temperatures are caused by differing amounts of solar insulation. So, warm or cold, you're still going to get convection cells in the atmosphere, you're probably still going to get a jet stream, and you're probably going to get fronts moving across continental landscapes due to irregular cooling and warming during the winter and summer months compared to the nearby water areas.
You're still going to have storms.
On top of that, in a point which you seem to be continually ignoring, the eventual outcome of Earth's temperatures in a thousand years is largely irrelevant to our own day and I have already acknowledged that, all other factors equal, the earth will end up doing all right if you ignore the intervening years.
The problem is that we will be living in the intervening years. And the problem there?
The Earth will not warm up evenly. So, unfortunately, YES, an increase in solar temperatures WILL end up making more funky gradients than ever.
Further: why is a desert a desert? Lots of people fall for the misconception that deserts are hot. They're not. At night deserts become literally ice cold. The average temperature in a desert is the same as in adjacent areas that are not desert. It's not daytime heat that eliminates the water and produces a desert--it's the other way around. It's loss of water that causes daytime heat. Lack of water (i.e. loss of insulation) is what causes the land to fry during the day and then lose all that heat at night.
*blinks again*
Well, yes, the lack of water stems from a high pressure band in a region between the two convection cells in the atmosphere, which dries out the landscape and makes it a lifeless hellhole, providing little forest cover and utterly lacking the moderating influence of open water.
While you have managed to finally demonstrate scientific competence, the point is
utterly irrelevant to the problem of climate change.
More greenhouse gas means a warmer and more stable climate. Which is a hodgepodge of good and bad things. And I never listen to people who only list the bad things; the mere act of doing that is a gigantic red flag. (I myself am highly skeptical of global warming, yet instead of pointing out only the good things about it and ignoring the bad, as most global warming skeptics might be expected to do, I say "it's a hodgepodge of good and bad things"; that's how you know I'm on the level)
No, saying, "It all evens out!" does not mean you're taking the rational point of view. Moderation between two extremes does not automatically grant you the upper hand morally. e.g. If you take the median between the two extremes between condoning and condemning murdering people you're not going to be making a very rational choice.
Because, frankly, sometimes it does
not even out.
And sure, in the long run, as I have, in fact, repeatedly acknowledged in numerous climate change "debates", the Earth will be fine! The period before the Cenozoic was pretty darn fun, and the Earth in, say, a thousand years, will look rather attractive, with new open lands in Antarctica, new seas, etc.
But you are missing the point and until you address it adequately you can never be taken seriously on this issue:
We do
not get to skip the next thousand years. We, personally, will live through much of the next century. And while gaiogenic climate change happens over very long timescales,
anthropogenic climate change happens over a very short scale. The wild increase in temperature will lead to freak weather, as explained above, rising sea levels, large-scale population displacements, declining river flows, and potentially massive climate problems on a continental scale.
We have to live through this.
This is the problem that anthropogenic climate change poses. You can't rationalize around it, and you can't just hope the problems go away. Islands are going to submerge, nations are going to move, there will be feasts and famines, and a lot of people will want to kill other people. We
need to plan for the future. So don't whitewash it all, saying, "it'll even out eventually!" Because we're talking about human lives here, and cultures, and societies, under threat.