Absolute baloney. The glacier level did not drop below the 1700 level until 1870. After 1700 there was a slow build up which then started reversing in 1820. Obviously none of this had to do with human CO2 emmsions from fossil fuels. It could be natural or due to changes in Earth's albedo from farming, fire or volcanic activity. This is the key issue with models, they strain our computing capacity and they can't account for every variable we can think of especially random events, events that we can't predict, or events for which we have little or no data (such as past farmland to forest ratios). Expecting a model to predict the planets temperature profile every year exactly is a ridiculous bar. Looking at 5 and ten year trends is more rational and even those will be off due to random events from time to time.

As for slope that's not relevant when you are looking at entirely different measures. Look at the pattern. It's not perfect, but real world data from complex systems seldom is.

Regards,
Mark