Skeptics of climate change have been given a fresh round of ammunition in the wake of recently exposed emails from the University of East Anglia's Climate Research Unit (CRU), dubbed the climategate scandal.

The practices of climate researchers are being called into question as emails show how scientists worked together to quiet dissidents, suppress information, and collaborate to advocate preconceived conclusions.

While nothing in the leaked email episode indicate global warming is a hoax, it gives weight to what skeptics have long called politically motivated and biased science.

The following are major arguments against climate change that come from the climategate documents.

The data used is not good, and has been manipulated, therefore all conclusions are not to be believed

Scientists, led by Dr. Phil Jones at the CRU, are charged with reconstructing the earth's climate profile deep into the past, when no measurements of the weather are actually to be found. The discipline, called paleoclimatology, uses proxy data to estimate temperatures when instrumental data was not available. This means, instead of reading a measurement off a thermometer, they used the sizes of tree-rings instead to estimate what the temperature must have been.

But where the tree-ring data and instrumental data overlapped from 1960 and on, the proxy data showed a decline in temperatures, while instrumental data showed an increase. This is where the infamous trick was deployed to hide the declines.

In fact, some computer code the researchers used even print reminders that the data has been manipulated: 'IMPORTANT NOTE: The data after 1960 should not be used. The tree-ring density records tend to show a decline after 1960 relative to the summer temperature in many high-latitude locations. In this data set this 'decline' has been artificially removed in an ad-hoc way, and this means that data after 1960 no longer represent tree-ring density variations, but have been modified to look more like the observed temperatures. 'NOTE: recent decline in tree-ring density has been ARTIFICIALLY REMOVED to facilitate calibration. THEREFORE, post-1960 values will be much closer to observed temperatures then they should be which will incorrectly imply the reconstruction is more skilful than it actually is. See Osborn et al. (2004). [sic] '

If the relationship between proxy and actual instrumental data breaks down at a certain point, it would be difficult to justify if the relationship was sound before that date.

It's not just the CRU, but climate model institutions have colluded together to falsify data

The CRU isn't the only institution that analyses and builds historical climate models.

CRU teams with the Hadley Center for Forecasting at the UK Meteorological Office to produce its findings, while NASA's Goddard Institute for Space Studies works with NOAA's National Climatic Data Center, in the US to generate another set.

Proponents of manmade global warming say even if there was a chance that CRU data was compromised, the data from the other institutions arrive at similar institutions, and therefore the science behind the IPCC reports remains sound.

The clearest evidence is in the emails themselves, which record a continuing conversation between a couple of dozen leading climatologists on both sides of the Atlantic over at least a decade, said Christopher Monckton, a former adviser to Margret Thatcher.

The emails show the team went out of their way to subvert the release of information and destroy evidence

In 2003, two Canadians, retired engineer Stephen McIntyre and University of Guelph economist Ross McKitrick, began to doing their own review of climate science but was met with walls of resistance from the CRU team and their associates.

American scientists -- -Michael Mann, Raymond Bradley, and Malcolm Hughes -- 5years prior had published a graph in Nature magazine showing a temperature reconstruction between 1000 to 1900 (stick) that was relatively flat, with a sudden rapid incline in temperatures from 1900 to 2000 (blade).

McIntyre and McKitrick questioned the science and eventually requested the raw data and computer code of which Mann's work was based to be released from the CRU. They weren't

Some of emails suggested that the CRU delete emails related to their work on the IPCC process to shield them from FOIA requests and actually destroy raw data in the face of a successful FOIA requisition.

A 2005 email from Phil Jones reads:

The two MMs [McIntyre and McKitrick]have been after the CRU station data for years. If they ever hear there is a Freedom of Information Act [FOIA] now in the UK, I think I'll delete the file rather than send to anyone.

Jones eventually did receive a FOIA request from McIntyre, and a 2008 email from Jones to Ben Santer--a climate researcher at Lawrence Livermore National Laboratory--illustrates how the case was treated.

I am supposed to go through my emails and he can get anything I've written about him. About 2 months ago I deleted loads of emails, so have very little--if anything at all.

There were doubts on warming, even within the CRU linked scientists, showing even internally there was no 'consensus'

The three American scientists that produced the infamous hockey stick graph needed data to produce to work with, and emails show them in discussion with Jones and other CRU scientists to find a solution.

Their discussion led them to CRU scientist Keith Briffa, who carried out a long term tree-ring proxy analysis in the past. He knew what they wanted, but expressed his doubts.

In an email dated September 22 Briffa says:

I know there is pressure to present a nice tidy story as regards 'apparent unprecedented warming in a thousand years or more in the proxy data' but in reality the situation is not quite so simple. I believe that the recent warmth was probably matched about 1000 years ago

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