Who Am I? Name: Zong-Liang YANG Professor, Jackson Chair in

Who Am I? Name: Zong-Liang YANG Professor, Jackson Chair in Earth System Science Director, Center for Integrated Earth System Science Education: BSc and MSc in Meteorology PhD in Atmospheric Science Research: Land Surface Modeling, Model Development & Evaluation Land–Atmosphere Interaction, Climate Modeling, Climate Change and Impacts on Water Resources and Environment Teaching: Living with a Planet; Earth, Wind and Fire Physical Climatology; Climate: Past, Present and Future Hydroclimatology; Land–Atmosphere Interaction Dynamics Email: Office: Hours: [email protected] JGB 5.220DA Friday 12:45-1:45pm or by Appointment

My Education and Work Places China He’nan Province: 16 years Nanjing: 5 years Shanghai: 1 year Australia Melbourne: 3 years Sydney: 4 years USA Tucson: 8 years Austin: 13 years

Introduction The scope of climatology Derived from Greek terms: klima logos slope (reflecting the early idea that distance from the equator alone drove climate ) study Study physical aspects of the interaction of the atmosphere with other spheres (lithosphere, hydrosphere, cryosphere, and biosphere); focusing on large scale (1000-km or above).

GEO 377P/387H Physical Climatology Textbook: Hartmann, 1994. Global Physical Climatology 12 chapters, 411 pp. Textbook: IPCC, Climate Change 2007: The Physical Science Basis 11 chapters, 940 pp. Course website http://www.geo.utexas.edu/courses/387h Click Schedules for lists of lecture topics, reading assignments and homework. Click Syllabus for Grading Policy. Office hours: Friday, 12:45-1:45pm or by appointment, JGB Room 5.220DA http://www.ipcc.ch/publications and data/ ar4/wg1/en/contents.html Special Report: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) http://www.ipcc-wg2.gov/SREX/

Chapter 1: Introduction to the Climate System This lecture discusses: 1. What are the components of Earth’s climate system? 2. How does climate variability differ from dayto-day weather? 3. What factors drive changes in Earth’s climate? 4. How does the climate system work?

The Habitable Earth The earth is the only habitable planet in our solar system. Oceans: 70% of the surface Land: 30% Earth’s climate is favorable to life. In the era of population explosion, climate change is critical to human life.

Weather versus Climate Weather The condition of atmosphere at a given time and place Short-term (and large) fluctuations that arise from internal instabilitie of the atmosphere Occurs as a wide variety of phenomena that we often experience Effects are immediately felt Social and economic impacts are great but are usually localized Many such phenomena occur as part of larger-scale organized system Governed by non-linear chaotic dynamics; not predictable deterministically beyond a week or two

Weather versus Climate Climate Defined as the average state of the atmosphere over a finite time period and over a geographic region (space). Can be thought of as the “prevailing” weather, which includes the mean but also the range of variations The wide range of natural variability associated with daily weather means small climate changes are difficult to detect Intimate link between weather and climate provides a basis for understanding how weather events might change under a changing climate Climate is what you expect and weather is what you get. Climate tells what clothes to buy, but weather tells you what clothes to wear.

Weather and Climate

Climate change nd its manifestation in terms of weather (climate extremes)

Climate change nd its manifestation in terms of weather (climate extremes)

Climate change and its manifestation in terms of weather (climate extremes) Global warming increases he frequency and intensity of extreme weather events

Climate Change in Texas from WCRP CMIP3

Climate Change in Texas from WCRP CMIP3 More heavy rainfalls and more floods More dry periods and intense droughts

Climate versus Weather Climate Defined as the average state of the atmosphere over a finite time period and over a geographic region (space). Can be thought of as the “prevailing” weather, which includes the mean but also the range of variations The wide range of natural variability associated with daily weathe means small climate changes are difficult to detect Intimate link between weather and climate provides a basis for understanding how weather events might change under a changing climate Involves atmospheric interactions with other parts of the climate system and external forcing Climate prediction is complicated by considering the complex interactions between, as well as changes within, all components

Climatic Controls The world's many climates are controlled by the same factors affecting weather, a) intensity of sunshine and its variation with latitude, b) distribution of land and water, c) ocean temperature and currents, d) mountain barriers, e) land cover, f) atmospheric composition. This map shows sea-level temperatures ( F).

The Climate System Components

Climate System Components Atmosphere Fastest changing and most responsive component Previously considered the only “changing” component Ocean The other fluid component covering 70% of the surface Plays a central role through its motions and heat capacity Interacts with the atmosphere on days to thousands of years Cryosphere Includes land snow, sea ice, ice sheets, and mountain glaciers Largest reservoir of fresh water High reflectivity and low thermal conductivity Land and its biomass Slowly changing extent and position of continents Faster changing characteristics of lakes, streams, soil moisture and vegetation Human interaction agriculture, urbanization, industry, pollution, etc.

Climate: Forcing and Response Input Machine Output

Forcing and Response: A Bunsen Burner Experiment Three major kinds of climate forcing in nature: Tectonic processes Earth-orbital changes Changes in Sun’s strength Anthropogenic forcing Urbanization Deforestation Burning fossil fuels Agriculture Response time depends on “materials” or “components”.

Response Times of Various Climate System Components

Feedbacks A feedback is a mechanism whereby an initial change in a process will tend to either reinforce the change (positive feedback) or weaken the change (negative feedback).

Example of a positive feedback Think about the polar regions:

Example of a positive feedback More energy retained in system Albedo decreases Less solar energy reflected Warm temperatures Ice and snow melt If this were the only mechanism acting, we’d get a runaway temperature increase

Example of a negative feedback More energy retained in system Albedo decreases Less solar energy reflected Warm temperatures More evaporation More clouds

Example of a negative feedback More energy retained in system Albedo increases More solar energy reflected Warm temperatures More evaporation More clouds

Another Positive Feedback More energy retained in system More longwave energy absorbed Warm temperatures More evaporation More clouds

Snow and ice albedo feedbacks in the polar regions are to blame for the large changes already observed. 1997 Ninnis Glacier Tongue Antarctica 2000

Mechanisms of Climate Variability and Change: External versus Internal Forcing External Changes in the Sun and its output, the Earth’s rotation rate, Sun-Earth geometry, and the slowly changing orbit Changes in the physical make up of the Earth system, including the distribution of land and ocean, geographic features of the land, ocean bottom topography, and ocean basin configurations Changes in the basic composition of the atmosphere and ocean from natural (e.g., volcanoes) or human activities Internal High frequency forcing of the slow components by the more rapidly varying atmosphere Slow variations internal to the components Coupled variations: Interactions between the components

Factors that influence the Earth's climate