1. Truth, lies, and uncertainties Philip Mote JISAO Climate Impacts Group University of Washington What we know and don’t know about global and regional climate change

2. Truth (beyond dispute) Greenhouse gases warm the Earth Humans are increasing the amount of greenhouse gases Earth is warming

3. Lies (and half-truths) Humans can’t affect CO 2 because the natural fluxes are so large Earth isn’t warming: urban growth Earth isn’t warming: satellites prove it The warming is natural (sunspots) A warmer world will be (all) good A warmer world will be (all) bad

4. Assessments: authoritative statements Thousands of peer-reviewed papers – the bricks of knowledge Peer-reviewed assessment: Intergovernmental Panel on Climate Change (IPCC) Major reports in 1990, 1996, 2001 National Academy of Sciences panel, 2001 underscored IPCC conclusions for President Bush

5. carbon dioxide concentration has increased by ~32% the carbon budget: nature has absorbed roughly half our emissions there is no question that the increase is unnatural from a very long term perspective, these changes are enormous Humans will keep increasing GHGs (IPCC: certain)

6. Some evidence that Earth is warming (IPCC:90-99%) Thermometers show warming of 0.4-0.8°C (0.7-1.4°F) since 1900 Arctic permafrost is melting Worldwide, most glaciers melting Arctic ice thinning Spring coming earlier (snow cover; blooming, leafing- out dates) Borehole temperatures indicate warming But: not every station shows warming; upper-air temperatures not increasing (satellites, balloons)

7. Global average temperature 18601880190019201940196019802000 0.8 0.4 0 -0.4 -0.8 degrees Celsius

8. “Drunken forest” in Siberia – trees tilt because of melting permafrost

9. Terminus of Nisqually Glacier in 1895

10. Some evidence that humans are responsible (IPCC: 66-90%) Rate of warming unusual (see next slide) Hard to explain as natural (volcanoes, solar, ocean) Pattern of warming (and stratospheric cooling) consistent with human influence

11. The earth is warming -- abruptly

12. Natural Climate InfluenceHuman Climate Influence All Climate Influences

13. Projections into the future Projections of future greenhouse gases (depends on socioeconomic projections) Climate models: different “sensitivity” Wide range of estimates: 1.4-5.8°C (2.5- 10.4°F) by 2100, faster than any time in at least 10,000 years (IPCC: 90-99%)

15. Temperature trends in the PNW Almost every station shows warming (filled circles) Urbanization not a major source of warming

16. PNW average temperature

18. Conclusions The bulk of the evidence points to a human influence on climate, with a global warming of 2.5-10.4F likely in the next 100 years. Regional warming likely to be faster than global warming (3-6°F by 2040s); main vulnerability: reduced snow leading to summer water shortages