I haven't written much on climate change, mainly because it's incredibly complex (simplistic Al Gore movies aside) and I'm hardly qualified to tease it all out. But it's a topic I needed to think about for my upcoming book on marine life. Among the sources I've perused, this is a very helpful one. A couple of graphs in this story have been useful in grasping the basic thrust of what's going on. The first lists the hottest years on record, and there's an irregular but dominant trend of such years clustering toward our present day, The second is the slowdown in the rise of surface temps, the Global Land-Ocean Temperature Index.
These obviously seem to be at least partly contradictory. The current belief among most climatologists is that the heat is being absorbed by the deep oceans and is gradually warming the subsurface water, not the surface where we do our measuring.
I posted a comment asking why the "switch" from surface warming to ocean warming might have taken place: The article here says Pacific wind circulation is most likely to blame: see the ADDED note below for another response.
There are a few other things I understand so far, or at least I think I do.
One opinion I've formed is that climatologists can be their own worst enemies. Things like the East Anglia climate emails seem to me to indicate a desire to make good science look like perfect science, to take a public view that all questions were settled when they are not. I agree the overall trend of the last century or two (how's that for precision) is toward a slow warming, and I agree that human activity is playing a role. It's not believable, though, to read a boiled-down statement that warming will increase X degrees and that human activity accounts for Y of those degrees when there are all kinds of variables. Some publications explain this, others do not. Part of that is the media summarizing complicated reports by bodies like the IPCC in a paragraph or a headline, but I think I detect an underlying feeling that "If we tell people there are doubts and variables, they'll dismiss the whole subject." Science is often messy.
This is a big planet under a myriad of intertwined and complex influences. No trend will be unambiguously clear. We should expect temporary flattening out, even the occasional reversal, of any tendencies in global temperature graphs. We should also expect very disparate local effects (such as some areas of Antarctica gaining sea ice while others lose it) regardless of what the big picture is.
These graphs are helpful in getting that big picture. But they also remind us that modeling something as complex as climate is not yet an exact science. No one predicted the recent leveling out in surface temperatures: those temperatures should, according to climatologists, have been rising more quickly if anything. Certainly models should be adjusted for real-world input: when the real world doesn't match the model prediction, you have to find out why and use that to improve the model. But you shouldn't have advertised the modeling publicly as near-perfect in the first place - even if you thought it was pretty good. Climatologists have tended to do that.
By the way, there's no excuse for labeling everyone who argues with the theory a corporate tool and a "denier" equavelnt to "Holocaust deniers" and saying they should be put on trial (which people I previously thought sane have actually advocated). Sometimes deniers have raised good questions. Honest dissent in science is as vital as free speech in politics.
One thing that is not deniable is that we are, in Carl Sagan's words, conducting a giant experiment on ourselves. There is no control group, no spare planet, just a one-time experiment with pumping combustion products into the atmosphere and seeing what will happen.
Logic is on the side of those who advocate restricting that experiment as much as possible. But they have to admit, as James Hansen tends not to, that there are real human costs in every course of action as well as benefits. There's not an inexhaustible sum of money in the "rich people" or "the developed world" that can be redirected with no negative impacts. Everything has costs and tradeoffs. Put $50M into converting a coal plant to natural gas, or put it into mosquito nets and vaccinations? Give electricity to rural Ghana, or forgo it if the economics require it be fossil fuel generated? This is hard stuff, and political leaders are not good at hard stuff. Everyone, scientists and Presidents and Congressmen and Prime Ministers and industrialists, have to agree that there is a problem AND that the answers require difficult choices.
ADDED: John Holman wrote back to me thus: "Ocean Heat Content Anomaly - It's the amount of energy being added to the oceans each year. The imbalance at the top of the atmosphere results in more energy coming into the earth system than leaving; hence, warming. In general, once heat is stored in the deep ocean it will not come back out until the imbalance at the TOA reverses: like in an ice age. What Trenberth means by "coming back out" is a period where of the amount of energy coming in, less goes into the ocean and more warms the atmosphere, and then goes back to outer space: a lower OHC anomaly and a higher SAT anomaly. Also known as periods of ocean dynamics that tend to warm the SAT. The atmosphere does not store much energy. That is why running trend lines off of 1998, or any other hottest year, is as stupid as it gets."