I came across a comment that simply must be addressed.
"During 2001 the IPCC made a number of predictions as to what would happen as a result of the climate change. It now turns out that the actual effects measured today are _worse_ than what was predicted. For example, the rise of the ocean level is 80% greater."
This is shoddy science at its worst and the fact that this meme is actually catching on is disturbing, to say the least.
First of all, I have to laugh at the use of "For example". The writer is apparently unaware of the fact that the claimed 80% increase is the only one of the 2001 predictions that is being held up as coming to pass. It is, in fact, the only one being talked about because none of the other predictions are even coming close.
So has there been an 80% increase in sea level measured in recent years? In words of one syllable of less, no, there has not. The only way this 80% number is achieved is by using two different sources for the beginning and ending figures. The 2001 predictions were based on tidal gauge measurements. The current claim of an 80% increase is based on satellite measurements. Anyone else notice how those two sentences do not contain the same words?
The difference here is important. We have been collecting data from sea level tidal gauges for over 200 years in some places (for example, data exists for Amsterdam as far back as 1700). We only began using satellites to measure sea levels in the mid-to-late 1990s. If you're counting, that's just over a decade, which is where a major problem comes in. According to studies using the larger tidal gauge data set, sea levels can vary widely from decade to decade and it requires multi-decade observation of data in order to identify discernible trends and understand the margin of error. We haven't been collecting satellite data for decades - we've only barely started the second decade of satellite observation of sea levels - so we cannot make accurate trend predictions from nor do we have anything resembling an accurate margin of error with satellite sea level measurements.
What makes this situation worse is that data from the two sources do not agree with each other. We are told that satellite data indicates an 80% increase, but that uses tidal gauge data as a starting point, and using tidal gauge data as an end point indicates no increase at all. I repeat: If you use tidal gauge data for the starting point and tidal gauge data for the ending point, there is no measurable increase in the rate of sea level rise. Tidal gauge data shows a sea level increase of approximately 1.8 mm per year for the last century and tidal gauge data still shows a sea level increase of approximately 1.8 mm per year. There seems to be something funny in this 80% math.
There are those who will claim that satellite data is more accurate than tidal gauge data. That may or may not be true, but it doesn't alter the point here in the slightest. Satellite data could be the most accurate data ever collected in the history of data collection and it would still be wrong if it used disagreeing, non-satellite data as its starting point. Tidal gauge data indicates sea levels and sea level increases far below those indicated by satellite data. If you're on a diet, do you use two different scales calibrated in different manners and to different degrees to determine your starting weight and how much weight you lose over time? Of course not! You don't have to be a climatologist or a physicist to know that would not give you accurate results, yet that is exactly what is being done with this 80% increase claim. There can only be one logical result when you start with a source that is measuring low and end with a source that is measuring high: a grossly inflated and highly inaccurate "increase".