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IPCC report says 'human influence on climate is clear'

Hurricane FranHurricanes and other tropical storms will become more intense according to the IPCC report Climate Change 2013. Image courtesy of NASA.

The evidence for human influence on the Earth's climate is stronger than ever according to the latest report from the world's leading climate scientists. Members of the Intergovernmental Panel on Climate Change (IPCC) confirm that 'warming in the climate is unequivocal' and that 'human influence on the climate system is clear'. The report, entitled Climate Change 2013: the Physical Science Basis, was released at a press conference in Stockholm on 27 September addressed by UN Secretary General, Ban Ki-Moon.

'Unprecedented' climate change

The scientists paint a grim picture of a rapidly warming world unless urgent international action is taken to curb greenhouse gas emissions. In the most probable scenarios of future carbon emissions, average global temperatures by the end of the 21st century are likely to exceed 2°C relative to the period 1850-1900. Such a rapid rise would be unprecedented in the planet's climate history, and is widely thought to mark a tipping point for dangerous and irreversible climate change. The predictions are based on multiple lines of independent evidence, more and better observations of climate phenomena and improved climate models, and are the result of nearly seven years of research.

Thomas Stocker, Co-Chair of the Working Group that compiled the report, said that 'Heat waves are very likely to occur more frequently and last longer. As the Earth warms we expect to see currently wet regions receiving more rainfall, and dry regions receiving less, although there will be exceptions.'Global sea temps

Global sea temperatures will continue to rise during the 21st century, with heat penetrating the deep ocean and affecting ocean circulation. Image courtesy of NASA.

Key conclusions

Other headlines from the report include:

  • Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850. The period 1983-2012 was likely the warmest 30-year period over the last 1400 years.
  • Over the period 1901-2010 the global mean sea level rose by 19 centimetres.
  • Atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased to levels unprecedented in the last 800,000 years.
  • Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.
  • Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped.polar bears
The IPCC says it is 'very likely' that Arctic sea ice will continue to shrink and thin during the 21st century, increasing pressure on species such as the polar bear. Image courtesy of US Fish and Wildlife Service.

'We need to act now'

Responding to the report, Professor David MacKay, chief scientific advisor to the UK's Department of Energy and Climate Change said: 'We need to take action now, to maximize our chances of being faced with impacts that we, and our children, can deal with. Waiting a decade or two before taking action will certainly lead to greater harm than acting now.'