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Blame for global warming placed firmly on humankind

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  • Mike Neuman
    Blame for global warming placed firmly on humankind February 2007 NewScientist.com news service Catherine Brahic, Paris The 2nd of February 2007 will one day
    Message 1 of 1 , Feb 2, 2007
      Blame for global warming placed firmly on humankind
      February 2007
      NewScientist.com news service
      Catherine Brahic, Paris

      The 2nd of February 2007 will one day hopefully be remembered as the
      day the question mark was removed from the debate on whether human
      activities are driving climate change, said the head of the UN
      Environment Programme at the launch of the most authoritative
      scientific report on climate change to date.

      The new Intergovernmental Panel on Climate Change report says there
      is 90% certainty that the burning of fossil fuels and other human
      activities are driving climate change.

      "The word unequivocal is the key message of this report," said Achim
      Steiner, executive director of UNEP, adding that those who have
      doubts about the role of humans in driving the climate "can no longer
      ignore the evidence".

      The IPCC report says the rise in global temperatures could be as high
      as 6.4°C by 2100. The report also predicts sea level rises and
      increases in hurricanes. It is the work of 1200 climate experts from
      40 countries, who have spent six years reviewing all the available
      climate research. It was released in Paris, France, on Friday (read
      the 21-page summary here, pdf format). Listen to audio from today's
      press conference.

      The last IPCC report, issued in 2001, predicted that temperatures
      would rise by 1.4°C to 5.8°C by 2100, relative to 1990 temperatures.

      But the new report says temperature rises by 2100 could, in the most
      extreme scenarios, range from 1.1°C and 6.4°C. The most likely range
      is 1.8°C to 4.0°C (see figure 1, right), with the report predicting
      that 4°C is most likely if the world continues to burn fossil-fuels
      at the same rate (read the The impacts of rising global

      Melting, moving ice
      Rises in sea levels are predicted by the new report, threatening low-
      lying areas of land around the world. As the oceans warm, their
      waters expand, while rising temperatures also increase the melting of
      the ice sheets that cover Greenland and Antarctica.

      In 2001, the IPCC predicted that sea levels would rise by between 9
      88 centimetres by 2100, relative to 1990 levels. The new report says
      rises could range from 18 cm to 59 cm. The top end of the range
      corresponds to a fossil-fuel intensive future (see A1F1 scenario in
      Modelling the future climate: the baseline scenarios).

      But predictions of sea level rise are one of the most contentious
      areas of the report - very recent research has suggested that rises
      of up to 140 cm are possible (see Shorelines may be in greater peril
      than thought.

      The problem is that the understanding of how warming affects
      Greenland and Antarctic ice sheets remains limited, and they are
      predicted to be the most important contributors to change. Estimates
      of the straightforward melting of ice are incorporated in the IPCC
      report. But warming may also accelerate the movement of ice in
      glaciers into the ocean, perhaps by meltwater lubricating the
      undersides of ice streams.

      Susan Solomon, one of the report's lead authors, said there was no
      published research that quantified this effect, and so it was not
      included. But she added: "If temperatures exceed 1.9°C to 4.6°C above
      pre-industrial temperatures, and were to be sustained for thousands
      of years, eventually we would expect the Greenland ice sheet to melt.
      That would raise sea level by 7 metres."

      Climate change is also expected to affect the frequency and strength
      of tropical storms and hurricanes. The latest IPCC report says the
      activity of tropical cyclones is "likely" to increase over the 21st
      century. It says "likely" indicates a probability of more than 66%.
      This is a bolder statement than the World Meteorology Organisation
      issued in January.

      Precipitation patterns will change too by 2100, according to IPCC
      predictions (see figure 2, right). Mid- to high-latitude regions will
      see up to 20% more rain and snow, while the tropical regions will see

      Humans to blame
      Considering the human role in causing climate change, the IPCC report
      damning: "The understanding of [human] influences on climate has
      improved since the [2001] report, leading to a very high confidence
      that human activities" are responsible for most of the warming seen
      since 1950, says the report's summary for policymakers. "Very high
      confidence" is described as "at least a 9 out of 10 chance of being

      Before the industrial revolution, human greenhouse gas emissions were
      small, and the atmospheric concentration of carbon dioxide – the main
      greenhouse gas – was about 280 parts per million (ppm).

      Thanks largely to the burning of fossil fuels and changes in land
      use, such as agricultural exploitation and deforestation, the
      atmospheric concentration of carbon dioxide reached 379 ppm in 2005,
      says the IPCC.

      Gold standard
      The IPCC draws together the world's leading climate experts to review
      and assess all available research, under the auspices of UN
      Environment Programme and the World Meteorology Organization.

      The result of their assessment, which is done every five to six
      years, establishes what is considered the gold standard of consensus
      on climate change science.

      The latest IPCC report was written by hundreds of experts and
      reviewed by hundreds more, from 113 countries. It is being released
      in stages during 2007. The first chapter, released on Friday, deals
      with the scientific basis for climate change.

      The next two parts of the IPCC's 2007 assessment, plus a synthesis,
      will be released throughout the year. Part 2, dealing with the
      impacts of climate change and our vulnerability to those impacts,
      will be released in April. Part 3, to be released in May, deals with
      how we might mitigate these impacts.
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