Shrinking Ice: The Global Impact of Polar Warming World Meteorological Day Presentation Geneva 23 rd March 2007 Chris Rapley Director British Antarctic Survey Chris Rapley Director British Antarctic Survey

IPCC Fourth Assessment Report Climate Change 2007 : The Physical Science Basis – Summary for Policy Makers Atmospheric GHG concentrations far exceed levels of last 650,000y as a result of human emissions Warming of the climate system is Unequivocal Current climate forcing primarily Human Agreed by delegates of 113 nations

In a Warmer World Ice Melts

Global Warming - Amplification at Poles Ice-Albedo amplifier as ice and snow cover reduces Hansen et al

Arctic Sea Ice Cover Reduction of Arctic Sea Ice summer extent 1978 to 2006 ~8% per decade Accelerating? Ice-free during summer by 2050?

Opportunities

Sea Level Rise Potential 0.5m 7m 57m

Summer melt area increased on average by 25% from 1979 to 2005 Modest increased snowfall in interior Greenland Ice Sheet Surface Melt and Glacier Discharge Space radar and gravity data indicate that ice discharge by melting AND SLIDING increased from 1996 to 2005 Net contribution to sea level rise ~0.28mm/y Shepherd & Wingham 2007

Antarctica

Antarctic Peninsula Glacier Responses 244 glaciers : 87% have retreated over last 50y Cook et al., 2005

Antarctic Peninsula Ice Shelf Disintegrations Summer surface melting the key Northern ones absent 3-5ky ago Larsen B in place for 10(s)ky

Peninsula Warming and Ice Shelf Break-Up Progressive warming attributed to human-induced enhanced greenhouse effect and ozone hole Marshall et al (2006)

Glaciers accelerated Glacier stable Larsen B Collapse

Antarctic Surface Elevation Change

Pine Island Glacier Iceberg Calving Marine Ice Sheet How Much? How Quickly?

2005 Survey by BAS and U. Texas

How Much? Ice accessible for discharge ~1.5m msl equivalent

How Quickly? Current Antarctic sea level contribution: –0.2mm/y (IPCC 2007) –0.07mm/y (Shepherd and Wingham 2007) Numerical ice sheet models provide no insight: –Ice dynamics not included –Numerical stability problems near grounding line

Sea Level Rise since Last Glacial Maximum 9k years at ~10mm/y two bursts at ~20mm/y or greater last 3ky to 0.2mm/y since mm/y last decade ~3mm/y

Predict m by 2100 BUT - models exclude increased ice sheet dynamical flow Even if GHG concentrations stabilised sea level rise will continue for centuries o C global warming if maintained for millennia would result in virtually complete elimination of the Greenland ice sheet and sea level rise of 7m. Comparable to interglacial period 125ky ago when polar land ice extent reduced and sea level 4-6m higher IPCC Fourth Assessment Report Climate Change 2007 : The Physical Science Basis – Summary for Policy Makers

Long-Term Commitment

Impact of Sea Level Rise Rowley et al 2007

Global Impacts Population Affected –1m ~ 110M –6m ~ 430M Cost?

Impact on Major Cities - London Estimated bill for one flood : £30bn = 2%GDP

Is This The Future?

International Polar Year

An intensive burst of internationally coordinated, interdisciplinary, scientific research and observations focussed on the Earths Polar regions

Intensive Observations

IPY Legacy International Year of Planet Earth International Heliophysical Year EXISTING POLAR ACTIVITIES Electronic Geophysical Year IPY SNAPSHOT LONG TERM IMPLEMENTATION IPY PLANNING IPY OBSERVING SYSTEMS

Observing networks established or improved during the IPY should be kept in operational mode for as many years as possible to provide data for the detection and projection of climate change (Recommendation of WMO EC–LVI, June 2004) Observing networks established or improved during the IPY should be kept in operational mode for as many years as possible to provide data for the detection and projection of climate change (Recommendation of WMO EC–LVI, June 2004)

If the Earth were only a few feet in diameter, floating a few feet above a field somewhere, people would come from everywhere to marvel at it. … they would declare it as sacred because it was the only one, and they would protect it so that it would not be hurt. Joe Miller