I teach, and when my students ask me questions, I never laugh at them, no matter how basic or "stupid" the question (or statement) is. They are trying to understand, and I have no problem with that. I'll do my best to help.
But when I meet people, online or in person, who have no interest in learning, but rather think that they can devise in 15 minutes, a better (and incredibly simple and obvious) "theory" than what professionals working their entire lives on the question, I am forced to conclude that they simply think everyone around them is stupid and they are smarter than everyone. These people aren't interested in anything but feeding their own ego, and it thrives on their own ignorance. Challenging them to their face isn't worth it. And certainly not in 140 characters.
But here, let's demolish the whole idea that there is a 789 year cycle that explains global warming/climate change, shall we?
Problem 1: no cycles in nature are exactly 789 years. An 800 year cycle would be more believeable in the sense that 800 sounds like an approximation. 789 sounds like an exact value, and nothing in nature is that exact. Even the orbits of planets wobble a bit. And complex systems driven by interactions with many things are even worse.
Problem 2: on page 1 it suggests that scientists have only been telling us about climate change for 10 years. Call bullshit bullshit, people. Global warming was originally proposed in 1895.
Problem 3: Let's go back to that 789 year cycle; they say: The cycle started on the 21st of December 1223 and ends on the 21st of December 2012. What can I say? This just confirms Problem #1, but it actually makes it worse, because they have exactly two data points. You don't get a cycle from two data points. And besides, the Medieval Warm Period (which is surely what he's referring to here), has been shown to be a local phenomenon only.
Worse, it goes on: The earth will then experience extreme weather conditions consisting of heavy torrential rain and snow. This will continue until the 21st of June 2013. I'm laughing even reading it, that someone takes it seriously. C'mon. June 2013... that sounds like an el Nino year, but what happens after that? Everything is hunky dory?
Problem 4: And oh, look! It's based on the Mayans!!
Problem 5: His charts don't make any sense, even when they exist. And frankly, I doubt we have the population data he claims to match up exponential growth as a "cycle". He totally ignores the Black Death, too.
Problem 6: He doesn't even understand the water cycle. How can he possibly hope to understand the carbon cycle?
Problem 7: The solution! Love it! He wants to evaporate sea water!!! Wait, water is a greenhouse gas....
Problem 8: He uses the Tsunami and clouds in Melbourne to prove his "theory"!
Problem 9: "relative data" is what you use, Peter, and is not the same thing as "relevant data" which is what everyone else uses.
I could go on, but that's enough to make the issues clear. Get over yourself, Peter.