How is affecting and what does it mean for us?

Professor Tim Naish, Victoria University of Wellington, New Zealand 70% of the world’s freshwater 90% of the world’s ice 65m of global sea-level rise Coldest Highest

Driest

East Antarctic Windiest (+54 m) Ice Sheet (+3.4 m) Remotest Antarctica is the engine room for global ocean circulation • Ocean heat transport provides regulates our planets climate • Changes around Antarctica have global consequences Warming of the climate system is unequivocal (IPCC SPM, 2013) 2019 on track to be warmest year on record = +1.2 ℃

1℃ average warming of Earth’s surface The human influence is clear (IPCC SPM, 2013)

Today’s CO2 is 410ppm Highest for 3 million years 30 years

11,000 years 230 years Where has all the heat gone?

Heat into has goneocean into from the ocean 2 global warming

…also don’t forget 25% of the CO

Average surface temperature would have warmed by 36℃ without the oceans, instead of 1℃ 3 million years ago – The last time Earth had 400ppm carbon dioxide in atmosphere

+4m SLR +54m SLR

Today Computer model of 3 million years ago

Antarctica partially melted contributing +15m to global sea-level rise & Greenland ice sheet melted contributing +5m Sea-level rise is the clearest global consequence of anthropogenic climate change

20cm global sea-level rise since 1850 Sea-level is not rising evenly

Ocean heat, currents and climate

Gravitational and solid Earth deformation What is causing sea-level rise?

0.6 m

65m

thermal expansion

~2 m

IPCC AR5 2013

Melting of polar ice sheets is accelerating and will dominate sea-level rise Antarctica and Greenland are very different

Bed Ice flow topography Future fate of Antarctica’s ice sheets is one of the largest uncertainties in climate science

+4m SLR +54m SLR

About 20 m of global sea-level rise is locked up in the highly vulnerable parts of the Antarctic ice sheet and is already beginning to melt Antarctic ice sheet is the elephant in the room

Southern Ocean is warming Ice shelves are melting Antarctic ice sheet is the elephant in the room

Southern Ocean is warming Ice shelves are melting

Paolo et al. (2015), Science Pritchard et al. (2013), Nature Paolo et al. (2015), Science Paolo et al. (2015), Science Pritchard et al. (2013), Nature Paolo et al. (2015), Science Floating ice shelves hold back the Antarctic ice sheet

• Larsen B Ice Shelf, 2002 Sea-level will continue to rise but the future is deeply uncertain

20mm/y dynamic Antarctic ice RCP 8.5 sheet melting missing! (business as usual)

RCP 2.6 (Paris 1.5-2°C)

3mm/y

<1mm/y

30cm by 2060 Latest projections for global sea-level rise with new Antarctic ice sheet estimates =+ 1.2 m by 2100 2.22.0

DeConto & 2.01.8 But 5% chance of Pollard 2016 1.81.6 up to +2m

1.61.4

1.41.2 Golledge et al., 2015, Also Ritz et al., 2016, Nature 1.2 1.21.0

1.0 RCP 8.5 0.8 (m) 0.6 RCP 2.6 Paris target 0.4

0.2 If the West Antarctic ice sheet collapse North America and Europe will experience 30% more sea-level rise!

Carling Hay, Mitrovica et al. 2011 There is a tipping point in the Antarctic Ice Sheet at 1.5-2 degrees Celsius of global warming

Low emissions Paris future High emissions no policy future <1m SLR = 15m SLR How close are we to this tipping point?

• 1.5 degrees C in 10-15 years

• 2 degrees C in 20-25 years Global impacts of projected sea-level-rise

• IPCC SROCC Report, 2109 Coastal inundation by 2050 - Shanghai Coastal inundation by 2050 - London Mitigation – what is required?

Net zero emissions by 2050 for 1.5℃?

Net zero emissions by 2070 for 2.0℃? How are we doing doing?

• New Zealand not on track despite Carbon Zero Act • UK is on track

?

Source: A Reisinger, unpublished Adaptation decision-making in the face of deep uncertainty

Thames Barrier

St Petersburg Barrier

• 30cm by 2050 independent of scenario • 50cm by 2100 even with limiting global warming to 2.0℃? • BUT could be as much as ~2m by 2100 if policy fails