Chapter 1 Earth System and Climate System What are the components of the Earth system, especially Earth’s climate system? How does climate change differ from day to day weather? Climate variability and climate change? What factors drive changes in Earth climate？ 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.

Earth History Earth’s age: 4.55 billion years (Byr) This course focuses on only recent 10% of its age.

Schematic diagram of the Earth system, showing interactions among its four components.

Weather versus Climate The condition of atmosphere at a given time and place Short-term (and large) fluctuations that arise from internal instabilities 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 Governed by non-linear chaotic dynamics; not predictable deterministically beyond a week or two

Low Pressure High Pressure Anti-Cyclonic Turning: divergence leads to downward vertical motions. Cyclonic Turning: Convergence leads to upward vertical motions. Cold Air Warm Air

Impacts of Weather Figure 1.15

Impacts of Weather

Hurricane: Gustav in New Orleans. 2 Million people evacuated (Sep

Climate versus Weather 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 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.

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.

Review Questions Which of the following statements relate more to weather (A) and which relate more to climate (B)? 1. The summers in Prince George are cool and dry. 2. It is 30°C right now, partly sunny, and south winds 10 to 20 miles per hour. 3. September 2001 was the 2nd coolest September of record for Prince George International Airport. 4. The pressure now is 29.75 inches and steady, and humidity is 84%.

The limits of Weather Forecast and Climate prediction Weather forecast model tries to predict the future state of the atmosphere using the laws of physics given the current state (i.e., the weather now)

Lorenz Model

The limits of Weather Forecast and Climate prediction Climate can be viewed as concerning the status of the entire Earth system, including the atmosphere, land, oceans, snow, ice and living things that serve as the global background conditions that determine weather patterns. Long-term variations brought about by changes in the composition of the atmosphere are much more predictable than individual weather events. (the time when a woman die vs the average age of death of women in Canada)

Temperature anomaly forecast for Sep. Oct. and Nov., 2014 The confidence level of the forecast

Climate Variability vs Climate Change ENSC 425/625 4/20/2017 Climate Variability vs Climate Change

Climate Variability vs Climate Change Which of the following statements relate more to weather (A) and which relate more to climate (B)? 1. The summers in Prince George are cool and dry. (B) 2. It is 30°C right now, partly sunny, and south winds 10 to 20 miles per hour. (A) 3. September 2001 was the 2nd coolest September of record for Prince George International Airport. (B) 4. The pressure now is 29.75 inches and steady, and humidity is 84% (A).

How scientists study climate changes (1) spend much time to gather and analyze data from the kind of climatic archives. To publish results in peer-reviewed journals. (2) need to explain and interpret results – Hypothesis, theory. (3) Models

Components of the Climate System Five major components: air (atmosphere), water (hydrosphere), ice (cryosphere), vegetation (biosphere), and land (lithosphere). Major processes: energy cycle, water cycle, carbon cycle, …

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.

The climate system evolves in time under the influence of its own internal dynamics and due to changes in external factors that affect climate (called ‘forcings’). External forcings include natural phenomena such as volcanic eruptions and solar variations, as well as human-induced changes in atmospheric composition.

Climate Forcing: can be defined as an imposed perturbation of Earth’s energy balance. (1) natural forcing: luminosity of the sun; volcanic eruption; earth’s orbit (2) Anthropogenic forcing (fossil fuel burning) – greenhouse gases forcing (unit: )  changes in global temperature. Climate Sensitivity

Forcing and Response: A Bunsen Burner Experiment Flame is far enough away

Climate: An Engineer’s View Anthropogenic forcing Machine Output Input

Time Scales of Climate Change Earth’s climate changes all the time, e.g., last 300 Myr, last 3 Myr, last 50,000 yr, and last 1000 yr.

Main drivers of climate change (~ hundreds of years)