Climate talks: What difference will temperature rise make to the oceans?

The Guardian, based on IPCC and Met Office data, reports 4th December 2015: Negotiators in Paris are trying to craft a deal at the UN climate talks that will keep global temperature rise below 2°C. But what does that mean in reality — and what difference will a couple of extra degrees really make?


  • 2015 was the first year to reach this level


  • Many species and ecosystems with limited ability to adapt to higher temperatures will be subject to “very high risks” even with 2°C of warming.
  • At particular risk are species dependent on Arctic sea ice — such as polar bears and coral reefs.
  • Arctic sea ice extent in September falls by 43% in extent against the long-term average.
  • Sea levels rise by up to 55cm. They have already risen by around 20cm over the 20th century.
  • The oceans get more acidic, with the surface ocean pH decreasing by 15-17%.


  • Ocean acidification is much greater, with surface ocean pH decreasing up to 62%.

Above 4°C

  • The Arctic is nearly ice-free in summer, as early as 2050.
  • Sea levels rise up to 82cm.
  • Ocean acidification accelerates hugely, with surface ocean pH decreasing up to 109%.


Sources: IPCC, Met Office
The Guardian, 4th December 2015: For the full details, see

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