I take a slightly different tact on that whole front. Based on just the satellite-collected data, I'm perfectly happy stipulating to the fact that there's been a small, observable, upward trend in the global average temperature over the past century. However, we lack sufficiently data with sufficient accuracy OR precision to say whether the upward trend has any significance in terms of differences in historic climate shifts. Certainly we've seen sudden, massive shifts in climate within human history (e.g. the Little Ice Age) which were obviously not caused by human activity. Further, many of those sudden, massive shifts don't show up in our typical climate measurement techniques. Sticking with the Little Ice Age, we have huge amounts of data from human accounts to say that the entire planet cooled significantly during this period. Yet when we look at indicators like glaciers, they don't tell us anything about it.
Let's repeat that: with our current climatology methods and techniques, we can't find a 300-year long mini ice age that human beings around the planet all observed, and it only happened 350 years ago.
So yeah, when someone tells me "omg we've NEVER seen temperatures change so fast and it's because people and carbon and stuff!", it'd be laughable if the ignorance weren't so sad. We can't track a 300 year long mini ice age using the best techniques we have for reconstructing historical global climate changes, and we can't do it with the cleanest, clearest, easiest data. New flash, boys and girls, we know Jack F. Shit about what kinds of sudden shifts happened thousands of years ago, let alone millions of years ago. Any sudden shifts - ANY sudden shifts - are lost in the data smoothing. Using everything we have today, there's zero chance we'd be able to detect the warming that's happened over the past 100 years from AD2300.
Why is that important? It means we have no idea if the warming we're observing is anything abnormal. We don't know what's happened before now, we barely know what's happening right now, and we don't know what actually drives changes in the global climate. If we knew how the global climate functioned, we'd be able to construct a functional model of the climate, pop in historical data from around the world, and get pretty accurate results about the next several years or decades following the last year of data entered. What we actually have are models where you have to fudge the data going in and/or add arbitrary constants within the model to make the results reasonably accurate for more than about a year (which is a joke). Even when arbitrary constants and false data are entered into the models we have to skew them in the direction we know they ought to go, their results become completely wrong within 18 months to two and a half or three years. In other words, they don't work because we don't build them correctly because we don't actually know what drives the planet's climate. And I'm not even getting into issues like tree ring data which totally throw off the whole thing.
So we don't have good data, we don't have a functional understanding of the Earth's climate, and we're supposed to believe that humans are destroying the planet and making it uninhabitable. Worse, we're supposed to sign on to proposals intended to alter the course of Earth's climate change with horrifyingly misguided geo-engineering schemes. My God, some people actually want us to sit down at the controls of the machine we don't understand but which we need in order to live and to start smashing buttons on it because they're convinced (without any real evidence) that we hit a button along the way that caused a problem.
This is sheer idiocy on a scale beyond imagination. It's like putting a small child at the controls of a 747 mid-flight and screaming at him to fix the plane. The result can only be a predictable and stupendous catastrophe in which an arrogant, stupid species causes its own extinction and the extinction of much of the rest of the organized life on this world.
Humans are dumb.