This is one of those situations where understanding of science is lacking.

They saw the actual data deviating from projections, and started investigating why it was deviating. In the meantime, they noted that there's no reason to assume the deviation will sustain itself, so short-term predictions were adjusted but they just increased the margin of error on longer predictions.

What caused the deviation? The model had failed to account properly for how the southern Pacific Ocean interacts in terms of heat. You've heard of El Nino and La Nina, right? Under El Nino, the Pacific releases heat from deep underwater into the atmosphere. Under La Nina, the Pacific absorbs more heat from the atmosphere. Until the early 2000s, the world was experiencing El Nino. Then it switched to La Nina, and the rate of warming of the atmosphere dropped - it kept warming, but at a much slower rate, because the Pacific was absorbing more heat.

It switched back to El Nino in the middle of last year. So it shouldn't surprise anybody that the warming jumped back into action at full force - hence why there's articles talking now about how 2015 was the hottest year on record, up 0.16 C on 2014.

When they added this effect, which is related to what they call the "Trade Winds", into the models, it became a lot more accurate. And the long-term predictions didn't change much.

There was actually a second thing that was influencing the result, though - it turned out that there was a statistical flaw in the aggregation of the data - when this flaw was corrected, the reduction in rate of warming wasn't as significant as it was before the correction. It was a mathematical flaw, not an interpretation flaw, that was fixed, so this isn't a "fudging the numbers" kind of thing.

Note that the whole thing about the 97% wasn't to say "you should trust it, because scientists say so", it was to say "stop listening to those people who are arguing that it's not happening because of 'no consensus' or 'the science is still out'". It was about countering an existing political message, not about creating a new assertion. It's the science that says it's happening, the 97% statistic shows that it's not a controversial scientific conclusion - scientists, especially those with expertise in the field, aren't doubting the findings in large numbers. There will always be those who challenge any scientific theory or result, but the vast majority view the science as solid.

In other words, it's not "scientists say it, so it's true", it's "the science is solid, so scientists are supporting it".

Much like the creationism vs. evolution "controversy," global warming is only controversial amongst members of the general public. It is not a controversial theory within the sciences. This whole "debate" should never have been about the merits of the science itself, but instead it should have been about what policy measures we would take to solve the problems of a changing climate. Unfortunately, ideology seems to always trump evidence in the minds of many. It seems that certain belief systems are so revolted, so existentially terrified of the implications of science towards said belief system that they dismiss the science out of hand. I don't believe conservatives reject global warming because an objective assessment of the evidence on their part led them to reject it, but rather because the public policy implications of AGW are so repugnant to their belief in unfettered free markets that they choose to reject the science. Since they refuse to acknowledge that it's a problem, this leads them insist that all these scientists are engaging in a massive hoax and are presumably part of some nefarious cabal of "leftists/socialists/Marxists/[insert ism of choice]" whose goal is global domination.

I wasn't implying that they fudged the numbers. I was implying that they really don't understand the systems of the atmosphere enough to even make accurate computer models predicting future warming. They seem to have acknowledged this in the latest assessment report and aren't making computer model predictions anymore. In fact they really seem to have toned down the alarmism overall. I'm not sure if this is reflective of the latest evidence showing less need for alarm or if they have weeded out some of the activists that were authoring previous reports.

Physics remains the same in closed and open systems, but the models we use become increasingly complex in an open system.  It's possible to detect a decrease in temperature while carbon dioxide concentration increases, but then there must be another force more dominant than carbon dioxide.  Imagine I'm pushing a box in one direction.  In order to push the box in the other direction some one else must overcome the weight of the box and the force of my push.  If some one else only observed my force, they might believe that motion occurs in the direction opposite of the direction of the force.  But they'd be incorrect because they missed the opposing force.  

I'm nitpicking, but your listed carbon dioxide concentration is off by magnitudes...

Many factors contribute to the global temperature, but it would be unfortunate to ignore one due to its size.  It would take an aluminum sphere with a large volume to match the mass of a small lead ball.  Much like different elements have different densities, different gases will absorb and emit radiation more or less effectively.  I would be surprised if the fluctuations of the sun's emission (measureables) are not considered in models unless they are shown to have no effect.  

Also CO2 doesn't just stay as CO2 in the atmosphere, there are lots of chemical reactions in the atmopshere that occur which changes one thing to another.

They know. (see Ocean acidification levels).

You know those Vostok charts you posted never go above 300, while current ppm is over 400? 

Yes, but they don't know everything that happens is the point. And if you knew anything about the vostok charts you'd realise why, but to enlighten you, they're the data from ice cores, so are a historical record, we have a pretty good record for the past near 100 years, it's before that we have no idea, and that's what the vostok ice core mission is all about.