Science of global climate change and potential impacts Alan F. Hamlet Philip Mote University of Washington Climate Science in the Public Interest

Carbon dioxide: up 32%

U.S Total CO 2 emission s since 1950 in billions of tons European Union Russia 68.4 Ukraine 21.7 Poland 14.4 China 57.6 Japan 31.2 Australia 7.6 India 15.5 Kazakhstan 10.1 South Africa 8.5 Canada 14.9 Mexico 7.8 Trinidad and Tobago United Arab Emirate s Kuwait

Global Surface Temperature Variations

The earth is warming -- abruptly

Groisman et al., 2004

The South Cascade glacier retreated dramatically in the 20th century Courtesy of the USGS glacier group

Most glaciers receding (except where precipitation has increased sharply)

March 5 Larsen B Ice shelf Antarctica

20th century decline in NH snow cover R.D. Brown, J. Climate, 2000

Source: Mote et al. (2004) Trends in April 1 SWE

Human Causes or Natural Causes?

Natural Climate InfluenceHuman Climate Influence All Climate Influences

Human signal seen in climate change over North America, Asia and Europe (HC) Year

Future Projections

21 st century temperature change IPCC (

Sea level rise IPCC (

Impacts

1) Examples of “Minor to Moderate” Impacts Temperature-related discomfort (hot, humid summers) Increases in asthma or allergy symptoms Increased energy costs for air conditioning Loss of recreation opportunities (skiing, camping, fishing, boating on reservoirs) Increases in minor damages due to flooding or storm water drainage problems (e.g. flooded basements) Loss of snowpack, decreased water supplies, increased costs for water Coastal erosion, landslides, and increased insurance costs

2) Examples of “Serious” Impacts Large-scale precipitation changes resulting in droughts and floods (high $$ in developed world, high human costs in developing world) Large-scale forest disturbance (fire, disease, insects) Sea level rise and increasing storm surge risks (particularly in island states and the developing world) Spread of temperature-controlled diseases (e.g. malaria) Significant reductions in global fresh water supplies and/or increasing water quality problems Large scale ecosystem damage, loss of species diversity

3) Examples of Possible “Catastrophic” Impacts Rapid collapse of ocean circulation, or other irreversible, large-scale changes in climate. Permanent loss of soil or large-scale climate-related losses in arable land resulting in global famine. Catastrophic human health issues (e.g. world-wide plagues) Collapse of ocean ecosystems due to PH problems affecting primary productivity Global scale wars, genocide

Extras on PNW Snowpack and Water Supply

April 1 SWE (mm) Current Climate“2020s” (+1.7 C)“2040s” (+ 2.5 C) -44%-58% Changes in Simulated April 1 Snowpack for the Cascade Range in Washington and Oregon

Effects to the Cedar River (Seattle Water Supply) for “Middle-of-the-Road” Scenarios +1.7 C +2.5 C

Obs. Summer Water Availability is Declining 55 years Figures courtesy of Matt Wiley and Richard Palmer at CEE, UW

Effects of Temperature And Precipitation Effects of Temperature Alone Trends in April 1 SWE for the WA and OR Cascades -35% -23% -4.25% per decade -6.48% per decade

Transient SWE simulation from HadCM3 (A2) GCM run (with running 10 year average smoothing) Simulated from observed climate shows a declining trend of ~3KAF per decade ( ) HadCM3 simulated declines ~4KAF per decade Figure courtesy of Matt Wiley and Richard Palmer at CEE, UW

Length of ski season at Snoqualmie