By Environment Correspondent Alister Doyle

WARSAW, Nov 11 (Reuters) - The United Nation's panel of climate experts revised estimates of historical greenhouse gas emissions, made in September, both up and down on Monday but said the errors did not affect conclusions that time was running out to limit global warming.

More heatwaves, floods and rising sea levels are forecast in the report from the Intergovernmental Panel on Climate Change's (IPCC), which guides governments on shifting towards cleaner energy sources.

The panel had hoped to avoid more corrections after an embarrassing error about Himalayan ice-melt in its 2007 report.

"I don't see it as a significant change," IPCC chairman, Rajendra Pachauri, told Reuters on the sidelines of a Nov. 11-22 meeting of almost 200 nations in Warsaw, Poland.

Among changes, the IPCC revised down the cumulative amount of carbon emitted since 1860-1881 to 515 billion tonnes from 531 billion given in September, and revised up the amount emitted since 1750 to 555 billion tonnes from 545 billion.

Global emissions are now running at about 10 billion tonnes of carbon a year, meaning those change are equivalent to about a year to a year and a half of emissions.

"Errors in the summary for policymakers were discovered by the authors of the report after its approval and acceptance by the IPCC," it said in a statement.

It did not say how the errors had been made.

The IPCC says the world has emitted more than half the estimated 1 trillion tonne of carbon viewed as the maximum to keep temperatures within safe limits at below two degrees Celsius (3.6 Fahrenheit) above the period 1861-1880 with more than a two-thirds probability, it said.

Many experts say that the world has only a few decades left before breaching the IPCC safety limits unless tough action is taken to cut emissions.

When asked if the correction would affect the credibility of the IPCC, Pachauri said, "I don't think so."

The IPCC's September report said the probability that most climate change since 1950 is manmade increased to 95 percent from 90 percent in 2007.

Bob Ward, of the London School of Economics, said Monday's correction made little difference to the overall carbon budget of a trillion tonnes.

"Climate change 'sceptics' will no doubt desperately seize on these corrections and falsely allege that it undermines the whole report, but the public and policy-makers should not be fooled by such claims," he said in a statement. (Editing by Louise Ireland and Nina Chestney)

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  • Top 10 Most Polluting Countries

    In the following slides, find the top 10 countries with the greatest carbon dioxide emissions in 2011. Figures are estimates from the <a href="http://edgar.jrc.ec.europa.eu/overview.php?v=CO2ts1990-2011&sort=des9">Emissions Database for Global Atmospheric Research (EDGAR)</a>, a joint project of the European Commission and the Netherlands Environmental Assessment Agency. (Photo Getty Images)

  • 10. United Kingdom

    Estimated 2011 CO2 Emissions in metric tonnes: 470 million (Photo Getty/AFP/MIGUEL MEDINA)

  • 9. Indonesia

    Estimated 2011 CO2 Emissions in metric tonnes: 490 million (Photo Getty/AFP/ROMEO GACAD)

  • #8 - Canada

    Estimated 2011 CO2 Emissions in metric tonnes: 560 million (Photo MARK RALSTON/AFP/Getty Images)

  • #7 - South Korea

    Estimated 2011 CO2 Emissions in metric tonnes: 610 million (Photo CHOI JAE-KU/AFP/Getty Images)

  • #6 - Germany

    Estimated 2011 CO2 Emissions in metric tonnes: 810 million (Photo JOHANNES EISELE/AFP/Getty Images)

  • #5 - Japan

    Estimated 2011 CO2 Emissions in metric tonnes: 1.24 billion (Photo YOSHIKAZU TSUNO/AFP/Getty Images)

  • #4 - Russian Federation

    Estimated 2011 CO2 Emissions in metric tonnes: 1.83 billion (Photo KIRILL KUDRYAVTSEV/AFP/Getty Images)

  • #3 - India

    Estimated 2011 CO2 Emissions in metric tonnes: 1.97 billion (Photo ROBERTO SCHMIDT/AFP/Getty Images)

  • #2 - USA

    Estimated 2011 CO2 Emissions in metric tonnes: 5.42 billion (Photo by Kevork Djansezian/Getty Images)

  • #1 - China

    Estimated 2011 CO2 Emissions in metric tonnes: 8.7 billion (Photo PETER PARKS/AFP/Getty Images)