1 Changing Earth’s Climate

`The balance of evidence suggests that there is a discernible human influence on global climate ' Intergovernmental Panel on Climate Change (United Nations), Second Assessment Report, 1996

`There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activity' Intergovernmental Panel on Climate Change (United Nations), Third Assessment Report, 2001

`Most of the observed increase in globally averaged temperatures since the mid-20 th century is very likely due to the observed increase in greenhouse gas concentrations.' Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007

`Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.' Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007

Greenhouse Gasses Sunlight heats up Earth’s surface Earth radiates heat back into the air Greenhouse gasses absorb this heat and don’t let Earth’s heat out

Increased Greenhouse Gases Earth’s “cooling” system is “clogged”

Evidence from the Earth

9 Global mean temperature Global average sea level Northern hemisphere snow cover Observations of recent climate change

10 Global Instrumental Temperature Record 10 warmest years

Carbon Dioxide Concentration (ppmv) Carbon Dioxide Concentration

12 How we get data from the past – Deep ocean cores – Tree rings – Historical documents – Coral cores – Ice cores Reconstructing past climates

Reconstructed Surface Temperatures

Carbon Dioxide Concentration (ppmv) Mauna Loa, Hawaii ( present) Siple Station ( ) Past CO 2 concentrations

CO 2 (ppmv) Thousands of Years Before Present Present CO 2 concentration (383 ppmv) CO 2 concentration after 50 years of unrestricted fossil fuel burning (600 ppmv) Petit et al., 1999; Siegenthaler et al., 2005; EPICA Community members, 2004 Temp. Proxy

Sea level rising by thermal expansion AND ice melt Sea ice melting (Arctic and Antarctic) Glaciers melting worldwide Arctic and Antarctic Peninsula heating up fastest Melting on ice sheets is accelerating More severe weather (droughts, floods, storms, heat waves, hard freezes, etc.) Bottom line: These changes do not fit the natural patterns unless we add the effects of increased Greenhouse gasses Signs that global warming is underway

Earth is 1°F warmer than 100 years ago Not equally distributed – Some areas have warmed 11°F Weather becoming more variable and more severe Some climate change facts

18 Scientists have no doubt

Glaciers fluctuate with climate Glacier ice Sea ice 18,000 years ago Present

For over 30 years, scientists have predicted increased greenhouse gasses will cause unnatural changes By 2000 we have seen: TAntarctic sea ice break-ups TAntarctic Peninsula warming TArctic sea ice melting TFaster Arctic warming (11°F!) TMelting of small glaciers and ice caps TSea level rise Predicted changes of human climate change

21 Antarctic Sea Ice Break-ups

22 Antarctic Sea Ice Melting

23

24 Arctic Sea Ice Melting

Ice Extent Anomaly (10 6 km 2 ) Arctic sea ice extent

Melting of small glaciers and ice caps

27 Carroll Glacier

28 McCarty Glacier, Alaska

29 Muir and Riggs Glaciers

Kilimanjaro

32 Qori Kalis

Patagonia

~80% of world’s water supply Rapidly retreating worldwide Glaciers and ice caps gone by 2100 or sooner Major ice sheets also retreating Who cares about glaciers?

Sea-level rising Thermal expansion (warmer water expands and needs more space) Addition of water from melting ice Melting ice sheets –Greenland: 7.4 m (25’) potential –Antarctica: 74 m (250’) potential

Greenland satellite melt record

1 year of melt! R. Huff, J. Box, S. Starkweather, T. Albert This is how much ice melted in just one year.

38 Sea Level Rise Areas in red will be under water if all Greenland melts.

39 Earth if Antarctica melts

Sea-level rise

Fastest extinction rate of life on Earth in 65 Million years (1000x normal rate) Increased disease (e.g. asthma, malaria) Increased poverty and hunger Sea level rise More extreme weather – Droughts – Flooding – Heat-waves – Storms Additional consequences