It's significant because we've spent billions (and almost spent trillions) on a problem that doesn't exist - AGW. And this is from one of the leaders of the movement that created a false impression of that problem.
That is a very, very dramatic claim, and one that requires extraordinary amount of evidence. In order to say that AGW does not exist, the burden of proof is very much on you-- the body of scientific evidence confirming AGW is extensive and well-confirmed. You cannot simply say that because fighting AGW is expensive, it can't exist, which is in essence what is being done.
By the way, citing the Daily Mail doesn't count as providing an extraordinary amount of evidence. The Daily Mail has made their position on this issue very clear, and has shown that they will lie and cheat to embarrass scientists at every turn. Since their reporting here does not cite original sources, the article simply cannot be taken at face value. Even if they were being completely honest here, one scientist saying something to a reporter does not contradict the massive body of peer-reviewed studies demonstrating AGW. What it would show at the absolute worst is that you have a scientist that is willing to say stupid shit in front of a microphone. In order to support your claim, you would need at the very least to show that long-term warming has not occurred, or that if it has, it is completely natural. Since both such claims run counter to all that we know about the climate, you would need a lot of data on temperature records, CO2 levels, etc. and to convince us as to why all collected data is invalid.
It's AGW that is the extraordinary claim that needs extraordinary proofs. Ridiculously bad computer models with 'adjusted' data from cherry picked stations are not proof of anything, so we have no idea what our net contribution is to the temperature. And (if we can ever prove it), whether it will continue and if it is harmful.
That's quite the contortion. The computer models are not "ridiculously bad," and there is absolutely no credible evidence (that is to say, there's no evidence outside of the Daily Mail) to even suggest, much less prove, deliberate tampering of data. Moreover, that there is harm caused by the changes in our climate has also been very well established. I have little patience for continually rehashing the same unfounded assertions, so please be so kind as to show us the evidence of tampering. In other words, put up or shut up.
The models have obvious warming biased 'adjustments' built into them and there is no model, which when given the correct inputs at a point in time would successfully predict the climate for a following period of time. The 'Hockey Stick' graph, which eliminates the Midieval Warm period and the Little Ice Age is the most obvious sign of how bad the models are.
Thank you for citing your claims. Now I am not familiar with the particulars of the alleged manipulations by GISS in Australia, but I would note a few things. One, the analysis in your citation was missing any sort of error analysis, and so it is impossible to formulate a statistical hypothesis test of the claimed manipulations. Being a personal blog, I wouldn't expect more, but without that sort of detailed statistical analysis, the claims have very little weight to them. Second, climate change is not my area of scientific expertise, and so if there are errors in his analysis, I am not likely to notice them; thus, I refer you to a group of people who have expertise in this area: http://www.realclimate.org/. Third, even if the alleged claims are true, they are far from showing a systemic error in all climate data. Our understanding of climate change is far broader than GISS's efforts, even though they are important in that understanding. In any field of study, there will be errors and failures of the review process, and so to conclude anything about the validity of climate data as a whole would require some sort of evidence that the alleged manipulations are occurring on a large scale and across organizations. This has not been provided, and thus your earlier assertions are still not backed up by evidence.
On the issues of the the Hockey Stick, the Medieval Warm Period and the Little Ice Age, there is decidedly more to say that has been said by people much smarter than I. In particular, the scientists at realclimate.org have prepared excellent resources for those interested in learning more about these topics. For instance, with respect to the MWP, their guide available at http://www.realclimate.org/index.php/archives/2004/11/mediev... cites studies which show that the MWP is at least partially an effect of strong regional variations in temperature. Moreover, the same guide cites a review that provides evidence that the MWP is not an anomalous warming period. They have a similar guide for understanding the LIA available at http://www.realclimate.org/index.php/archives/2004/11/little....
Finally, I would refer you to http://www.realclimate.org/index.php/archives/2004/12/myths-... for more on the Hockey Stick, since you haven't provided me with any specifics on your claims that it has been manipulated to hide the MWP and LIA. In lieu of more specific claims, I think that the best I can do is to refer you to that comprehensive guide.
Some of the hacked emails from the University of East Anglia discussed how to manipulate discussion on realclimate.org by passing AGW-supportive comments through moderation quickly while allowing AGW-skeptical ones to linger indefinitely.
Is it responsible to keep assuming, then, that the ideas presented at RealClimate.org are a legitimate indicator of the state of scientific opinion on this topic? Can you provide links to other sources?
You should also moderate your tone. A lot. I've been reading and talking to people about global warming since the early 90s, and I'm strongly predisposed to take scientists at their word. If the stridency in your writing can make me want to close my laptop and take a nap, it's certain to stir up angry feelings in people who vehemently oppose to the idea of global warming. They will respond in kind, HN will get a little less civil, hence a little less useful for everyone. And you will bear part of the responsibility.
By the way, citing the Daily Mail doesn't count as providing an extraordinary amount of evidence. The Daily Mail has made their position on this issue very clear, and has shown that they will lie and cheat to embarrass scientists at every turn. Since their reporting here does not cite original sources, the article simply cannot be taken at face value. Even if they were being completely honest here, one scientist saying something to a reporter does not contradict the massive body of peer-reviewed studies demonstrating AGW. What it would show at the absolute worst is that you have a scientist that is willing to say stupid shit in front of a microphone. In order to support your claim, you would need at the very least to show that long-term warming has not occurred, or that if it has, it is completely natural. Since both such claims run counter to all that we know about the climate, you would need a lot of data on temperature records, CO2 levels, etc. and to convince us as to why all collected data is invalid.