To ask Her Majesty’s Government what assessment they have made of whether increases in the global mean sea level are inconsistent with reasonably expected natural variability; and whether there is any evidence for such inconsistency that is not based on computer simulations of the climate.
18 April 2017
Evidence that increases in the global mean sea level are inconsistent with natural variability can be found in the 5th Assessment Report from the Intergovernmental Panel on Climate Change (IPCC AR5). This states that it is very likely (> 90% probability) that human activities contributed substantially to global average sea level rise since the 1970s.
Instrumental and proxy data reveal that global average sea level began to rise above the long-term natural background rate in the early twentieth century. Our physical understanding of these observations and their attribution to human activity does not require computer simulations: the oceans have absorbed over 90% of the excess energy that has accumulated in the climate system from human greenhouse gas emissions, and the resulting thermal expansion of seawater accounts for 40% of observed sea level rise. Computer simulations of the climate provide further evidence that human influences, and not natural variability alone, explain these changes.