Professor Phil Jones: "I've obviously written some very awful e-mails"
MPs have quizzed the scientist at the centre of the "climategate" scandal, the first time he has been questioned in public since the row erupted.
Professor Phil Jones used his appearance before the science committee to say that he had done nothing wrong.
Earlier, critics told the MPs that the stolen e-mails, which appeared on the internet in November, raised questions about the integrity of climate science.
Lord Lawson called for scientists to be more open about their methodologies.
In November, more than 1,000 stolen messages between scientists at the Climatic Research Unit (CRU), based at the University of East Anglia (UEA), and their peers around the world were posted on the web, along with other documents.
Climate "sceptics" have claimed that the stolen data show that some researchers, including Professor Jones, have attempted to manipulate data in order to strengthen the argument that human activities are responsible for warming the planet.
They have also criticised Professor Jones for failing to make raw data and methodology available for public scrutiny, despite numerous Freedom of Information requests.
Question of trust
"The Freedom of Information Act should not have been brought into this," former Chancellor Lord Lawson of Blaby, a longstanding critic of climate policy, told MPs.
The e-mails were stolen or leaked from the University of East Anglia
"Scientists of integrity reveal... all of their data and all their methods. They don't need Freedom of Information Act requests to get this out of them."
Also giving evidence alongside Lord Lawson was Dr Benny Peiser, director of the Global Warming Policy Foundation.
He said that sound science was based on "testability, replication, and verification".
Dr Peiser told the committee: "Of course, if you do not have the data sets or methods then you have to trust the word of a scientist.
"You cannot even see if he has done these calculations directly on the basis of solid data, and this is the core of this problem - it is not about the overall science, it is about the process."
When asked if his organisation was planning to carry out its own modelling, he replied: "We are not in the business of climate modelling."
Professor Jones, who has stepped down as the director of CRU pending the findings of an independent inquiry, told MPs: "We have given them the finished product available from the very beginning but not the raw [weather] station data.
"Most scientists do not want to deal with the raw station data, they would rather deal with a derived product."
When challenged about the contents of one of the stolen e-mails in which Professor Jones told a critic of his work that he would not make information available because the data would only be used to undermine his findings, he admitted that he had written a number of "very awful e-mails".
Professor Edward Acton, vice-chancellor of UEA, told the committee that it was not possible to make the entire international data set available because of a "commercial promise".
He explained that a number of contributing nations - including Canada, Poland and Sweden - had refused to make their segments of data publicly available.
The committee is expected to publish its findings before the general election.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.