The GRIP (Greenland) borehole record is one of the best records because it is not a proxy, it is a DIRECT measure of temperature. Shown are the last 2000 years. (Dahl-Jensen et al. 1998, Science, 282, 268-271 "Past Temperatures Directly the Greenland Ice Sheet"). A similar reconstruction occurs for the Ural Mountain borehole temperatures (i.e. warmer 1000 years ago, Bemeshko, D., V.A. Schapov, Global and Planetary Change, 2001. We are probably not as warm as during Medieval Warm Period
1.Carbon Dioxide is a greenhouse gas, 2.it is increasing in the atmosphere (at ½ rate of human production), 3.therefore, the lower atmosphere MUST warm Global Warming Basic Hypothesis: CO2 concentration is now about => 40% above pre-industrial times.
Boundary layer Cooling (loss of IR radiation) by dry air to space warm, humid aircool, dry air evaporation removes heat Air sinks in response to precipitation systems: Sinking air is relatively dry Ocean or Land Heat released through condensation causes air to rise, rain falls to surface Most of our atmosphere is being continuously recycled by precipitation systems, which then determine the strength of the Greenhouse Effect Sunlight absorbed at surface
Outline Evidence for climate change Predictions of future climates Assessing response of natural ecosystems Future directions
Incoming Sunlight Emitted Infrared Radiation = GLOBAL WARMING BASICS: “Radiative Energy Balance” (= const. Temp.) => Greenhouse gases affect Infrared Radiation Global average input = output = ≈235 Watts per square meter
“Global Warming” (at least since 1920) is Real… But how unusual is it? How much of it is natural versus man-made? Data source: J. Hansen/ GISS “Little Ice Age”
GLOBAL WARMING: Early Warning Signs http://www.climatehotmap.org/ Fingerprints and Harbingers Heat waves and periods of unusually warm weather Sea level rise and coastal flooding Glaciers melting Arctic and Antarctic warming Spreading disease Earlier spring arrival Plant and animal range shifts and population declines Coral reef bleaching Downpours, heavy snowfalls, and flooding Droughts and fires