Climate Change Overview Rosina Bierbaum, Dean and Professor The Investor Forum on Climate Risk December 7, 2006
OUTLINE OF THE TALK • Climate change is a “matter of degrees” • The state of science • Future impacts on the US • Impacts already documented in Assessments • New and worrisome science • The size of the energy challenge • Pursuit of solutions
Climate Change: it’s a matter of degrees...
Human-induced radiative forcing will greatly exceed natural and pre-21st century increments
The two globes summarize computer simulations to compare the warming expected under a doubling of CO2 from the pre-industrial level with the warming expected from a quadrupling. Note that N hemisphere mid-continent average warming in the 4xCO2 world is 15-25°F! This is a roasted world. T changes for 2x CO2
Noxious Weeds Lythrum salicaria L.(Purple Loosestrife) Pueraria lobata (Kudzu) Alliaria petolata (Garlic Mustard)
India’s worst drought for 20 years left people struggling to find water. 2003. Nature 423:673
Increasing Confidence in the Science • IPCC 1990:The observed increase [in temperatures] could be • largely due to natural variability; alternatively this variability and • other man-made factors could have offset a still larger man-made • greenhouse warming. • IPCC 1995:The balance of evidence suggests a discernible human • influence on global climate. • IPCC 2001:There is new and stronger evidence that most of the • warming observed over the last 50 years is due to human • activities.
IPCC, 2001 Computer models of climate match observations only if natural forcings (sun, volcanoes) and human ones (GHG, particulates) are included. The human forcings are responsible for most of the rapid warming 1970-2000.
1000 years of Earth temperature history…and 100 years of projection IPCC (2001) scenarios to 2100
An Interesting Way to Present Predicted DT Probability Distributions Jacoby, MIT Jacoby, MIT
U.S. World Average
Climate change will have a range of impacts Health Impacts Weather-related mortality/heat stress Infectious diseases Air quality-induced respiratory effects Agriculture Impacts Crop yields and commodity prices Irrigation demands Pests and weed Climate Changes Forest Impacts Change in forest composition Shift geographic range of forests Forest health and productivity Temperature Precipitation Water Resource Impacts Changes in water supply and timing Water quality Increased competition for water Sea Level Rise Coastal Area Impacts Erosion of beaches Inundation of coastal wetlands Costs to defend coastal communities Ecosystem Impacts Shifts in ecological zones Loss of habitat and species Coral reefs threatened Adapted from EPA
Examplesof Regional Water Impacts Colorado River Basin: Decreased runoff will exacerbate salinity problems Shift in seasonality of runoff. Water deliveries may be dramatically affected Great Lakes: Avg. lake levels could fall by 2-8 feet Higher water temps could change thermal structure Increased dredging of ports could suspend toxic sediments San Francisco Bay: With sea level rise, flooding of Delta islands and marshes. Increased bay salinity and inland migration of saltwater Chesapeake Bay: Sea level rise will inundate most existing wetlands. Florida: Wetlands at risk Biscayne aquifer becomes salty; loss of shrimp, crabs, oysters, and other species California: Increased winter runoff, reduced spring and summer streamflow Decrease in water supply and reliability in Central Valley Basin. Great Plains: Pressure for more irrigation Surface runoff and erosion of pesticides and fertilizers may increase Louisiana: Sea level rise of over 4 feet by 2100 4,000 sq mi of wetlands at risk Increased vulnerability of coastal drainage and sewage systems Source: EPA, 1989; EPA, 1995
Wastewater systems that combine storm drains, sewage, and industrial waste are still used in about 950 communities, mostly in the Northeast and Great Lakes regions.
Warming Effects on Sockeye Salmon December Predicted ocean warming will alter suitable habitats. Temperature based on Canadian Climate Centre model. Blue: current range Red: 2090 range. July (Welch 1998)
Examples of Seasonal Climate Shifts UCS, 2003
The one degree average temperature increase over the last 100 years has not occurred evenly across the globe
Linear trends in the date of the last measurable snow on the ground. Dark areas indicate regions where these trends are statistically significant at the 0.05 level.
Mountain snowpack is declining Source: P. Mote, U. of Washington
Impacts of Climate Change Changing Forest Pathogen Distributions
Observed impacts of temperature-related regional climate change in the 20th century Studies using remote sensing Observation period longer than 20 years Rosenzweig, 25 Oct 2000
Emerging worries--Since the National Assessment (2000) and the IPCC Report (2001) • Rapid ice melt (Greenland and the Arctic) • Mortality from heat-waves & disease • increased intensity of major storms • increased frequency & intensity of droughts • increased frequency of great floods • change in species ranges & behavior • increased frequency & extent of wildfires • Increased cost of weather-related disasters
Shrinking Polar Ice Extent of Arctic summer ice in 1979 (top satellite image) and in 2003 (lower satellite image). NASA photograph
Greenland ice Melting 1992, 2002, and 2005 1992 2002 2005 In 1992 scientists measured this amount of melting in Greenland as indicated by red areas on the map Ten years later, in 2002, the melting was much worse And in 2005, it accelerated dramatically yet again Source: ACIA, 2004 and CIRES, 2005
Greenland & Antarctic • IPCC 2001 “central estimate” of ~0.5 meter further sea-level rise by 2100 now looks like an underestimate…maybe a big underestimate. • All the ice on Greenland ≈ 7 m increase in sea level; ice in WAIS ≈ 5 m.
Emerging worries (continued) • deadly heat-waves “[P]resent-day heat waves over Europe and North America coincide with a specific atmospheric circulation pattern that is intensified by ongoing increases in greenhouse gases, indicating that it will produce more severe heat waves in those regions in the future.” (Science 8/06/04)