From Global to Regional: Perspectives on Climate Change Radley Horton

1. From Global to Regional: Perspectives on Climate Change Radley Horton Columbia University Center for Climate Systems Research (CCSR) Climate Change in the Delaware Valley Philadelphia, PA May 6, 2008 CCSR

2. Outline • Introduction and Framework • Climate Projections • Impacts • Solutions CCSR

3. Framework for Climate Risk Assessment • Current and Historical Climate • Current climate trends, indicators, and variability. • Global Climate Models and Emissions Scenarios (Update ~5 years) • GCMs characterize climate uncertainty (IPCC AR4, 2007). • GHG emissions scenarios span a range of development futures - population, GDP, technology (IPCC, 2000). • - temperature, precipitation, sea-level rise • Regional Climate Scenarios for Key Variables • Statistically downscaled model-based probabilities characterize risks. • Regional climate model simulations provide a fuller picture. • Extreme Events • Frequency and intensity of heatwaves, rainfall flooding, droughts, and coastal storms. • High Impact Scenarios • Ice sheet melting and Arctic sea ice extent are monitored and evaluated. CCSR

4. IPCC, AR4

5. IPCC, AR4

6. Global Climate Models • Climate models are our best tool for predicting future climate • Models have improved dramatically with scientific understanding and computing power • But major challenges remain IPCC, AR4 CCSR

7. Figure SPM-4 IPCC, AR4

8. Climate Change Projections CCSR

9. IPCC Global Projections • Warming: 3.2o to 7oF by the 2090s • Precipitation: Drier subtropics, wetter mid/high latitudes expected • Sea Level Rise: 7- 23 in (excluding possibility of future rapid changes in ice flow) • Extreme events: More droughts, coastal floods and intense precipitation events Multi-model average temperature change (C), relative to 1980-1999, for scenario A1B Source: IPCC WG I, Summary for Policymakers, 2007 CCSR

10. Temperature (°C) Precipitation (mm/month) Regional Climate Models Observed Modeled CCSR, GISS, UCONN

11. 2020s 2050s 2080s Frequency distribution of temperature (°F), and precipitation (%) changes, relative to 1970-1999, 14 GCMs/3 GHG scenarios Model-Based Climate Probabilities CCSR

12. Sea Level Rise and Coastal Storm Surge Flooding • Climate change can influence area inundated through several effects, which require differing adaptations: • Because mean sea level rise will rise (due primarily to ocean warming, melting of land-based ice, and local factors) • During storms, surges will change regardless of whether storms themselves change. • Changes in intense storms may increase the magnitude of storm surges, superimposed on mean sea level rise CCSR

14. Extreme Events Temperature Very hot days may occur ~4 times as often in the 2050s……and ~7 times as often in the 2080s Very cold nights may be ~65% less common in the 2050s… …and ~85% less common in the 2080s Coastal Flooding Coastal flooding that currently occurs once every 5 years may average once a year in the 2050s Coastal flooding that currently occurs once every 10 years may occur 1-2 times per year by the 2080s Precipitation Intense precipitation is likely to become more frequent this century Changes in droughts are highly uncertain CCSR

15. Feedbacks and Possible Surprises Negative feedbacks that might minimize warming: An increase in thick, low clouds More sun-blocking airborne dust due to disturbed conditions Positive feedbacks that might increase warming: Greater surface absorption of sunlight as snow and ice melt Release of greenhouse gases from “permafrost” as it melts Decreased CO2 uptake by the ocean as it warms An increase in high, thin clouds More forest fires with heating release more CO2 Poleward forest expansion may cause more sunlight absorption Deep ocean warming might release greenhouse gases

16. Continuing Contact with Evolving Science Arctic Sea Ice (I) September 2007 September 2005 This September’s values were 36 % below the 27-year average, 23 % below the prior minimum, and approximately 50 % below the average values of the 1950s Source: National Snow and Ice Data Center CCSR

17. Arctic Sea Ice (II) March 2008 This March’s values were less than 5 % below the 27-year average, but variability is limited in late winter. Source: National Snow and Ice Data Center CCSR

18. Possible Long-Term Implications • Delay in the onset of fall and winter, and reduced severity of winter? • Changes in large-scale atmospheric circulation, including storm tracks? • Accelerated melting of the Greenland Ice Sheet/ Sea Level Rise?

19. Are we ceding control of atmospheric greenhouse gases? The more the climate system is altered, the greater the probability of surprises

20. Climate Change Impacts CCSR

21. Selected Relevant Impacts • Water • Quantity and quality • Human health • Changes in vector-borne diseases, heat/air quality-related mortality • Increased burden on health services • Infrastructure and Energy • Changes in severe weather events, possibly including tropical storms • Ecosystems • Wildfire risk • Loss of ecosystem services with decreases in biodiversity and populations of critical/endangered species • Indirect Impacts CCSR

22. Increased Streamflow Earlier Stream Flow Warming Lakes Projected "increases in annual mean streamflow in high latitudes …(medium confidence)“ TAR Hydrology and Water Resources • Increased runoff and earlier spring discharge from snow melt and glacial melt, Warming lakes and rivers

23. Marine and Terrestrial Ecosystem Phenology and Range Shifts Migration of biomes as discrete units is unlikely to occur; instead at a given site, species composition and dominance will change. Results of these changes will lag behind the changes in climate by years to decades to centuries (high confidence). TAR Poleward and elevational range shifts, Earlier onset of spring events, e.g. flowering, migration, lengthening growing season Without appropriate management, these pressures will cause some species currently classified as “critically endangered” to become extinct and the majority of those labeled “endangered or vulnerable” to become rarer, (high confidence). TAR Biological Systems

24. Impacts of Sea Level Rise • Infrastructure, residential and commercial assets are all at risk to SLR and more frequent coastal flooding • Inland flooding from rainfall will be more destructive due to drainage problems • Saltwater will intrude into estuaries and aquifers, and inundate polluted sites • Coastal ecosystems will be compromised CCSR

25. Climate Change Solutions

26. Ways to mitigate greenhouse gas emissions • Use less energy • Use less carbon-intensive energy sources • Less coal, no oil sands • More wind, solar, and geothermal. But what about biomass, hydroelectric, and nuclear? • Enhance carbon sinks • Encourage technological innovation and proliferation • Carbon tax vs. cap and trade system • Regulate (ex. fuel efficiency standards) • Lead by example

27. How can agencies adapt to climate change? • Understand current climate risks • Anticipate future climate change (and indirect impacts of climate change) • Design/plan for thresholds and ranges of forecast temperature, sea level, hydrology • Evaluate potential adaptations (cost/benefit, environmental impacts) • Insurance / hedging strategies • Stay abreast of evolving science CCSR

28. Other ‘Solutions’ • Climate Engineering • Aerosols and the stratosphere • Seeding of the ocean • Doing nothing

29. Conclusions • We do not know as much about climate or climate change solutions as we think we do • Uncertainty does not argue for inaction • Long-term planning can lessen negative outcomes of climate change, and increase positive outcomes • Adaptation and the new frontier • Climate of Fear? • Does every disaster have a silver lining? CCSR

30. Predictions • Climate of Fear? • Adaptation and the new frontier • Does every disaster have a silver lining?