According to the Intergovernmental Panel on Climate Change (IPCC) extreme events that used to have a return period of once every century could be happening on some coastlines every year by 2050.They reported that serious impacts in the world’s oceans and ice caps are inevitable. However, they also point out that impacts could be even worse without a reduction in fossil fuel emissions, including sea level rises of over 4 metres by 2300.
The oceans are under great threat from sea level rises, thermal expansion, acidification and less oxygenated than previously. This matters because approximately 2 billion people live next to coastlines. Even if global warming is kept to under 2C, rising sea levels will cause damage worth trillions of dollars and cause major environmental refugees.
The IPCC revised its 2014 predictions regarding rising sea levels due to an increase in melting of Antarctica. Without cuts in emissions, the IPCC predict that sera level will rise between 61 cm and 110 cm. This is an increase of 10 cm on the previous estimate. It matters because an extra sea level rise of 10 cm put an further 10 million people at risk of flooding. The worst case scenario suggests that sea levels could rise by up to 238 cm by the end of this century, leading to severe flooding in many megacities.
Even with cuts to greenhouse gas emissions sea level will still rise by between 29cm and 59cm due to the response lag time between increased emissions and melting of ice. The IPCC suggest that the impacts of increased sea level will be felt in many places before 2050.
In addition to rising sea levels, warmer oceans are causing more intense hurricanes. The rainfall that accompanied Hurricane Harvey in 2017 were made three times more like due to global climate change. El Nino events are predicted to become twice as frequent as in the past, while ocean acidification and declining oxygen levels in oceans could reduce fish catches by 25% and all marine life by 15%. Some ocean areas are faring worse than others – the Arctic, for example, has seen a major reduction in sea ice. This matters because the darker ocean surface absorbs more solar radiation than highly reflective ice, and this exacerbates global climate change