Image: January 2004 Blue Marble Composite – Reto Stöckli, NASA Earth Observatory Energy, space, and Earth's effective temperature Unit 1 of Earth’s Thermostat InTeGrate Module

Today, we are going to analyze temperature data by looking at anomalies. What is an anomaly?

An anomaly tells you how different a number is from the average value. What would a positive temperature anomaly indicate? What about a negative?

What you and your group should do for Part 1: Plot out the temperature anomaly data for your decade Draw a straight best fit line through your data, extending it outward to predict the anomaly in 2025 A best fit line captures the slope (or trend) in the data

What’s happening with temperature during this decade?

Slope is °/yr; temperature decreasing by.029° per year What would it be in 2025? -3.5°C anomaly in 2025

What happened to global temperatures in this decade?

Slope is 0.001°/yr; temperature increasing by.001° per year What would it be in 2025? 0.07°C anomaly in 2025

What happened to global temperatures in this decade?

Slope is °/yr; temperature increasing by.012° per year What would it be in 2025? 0.82°C anomaly in 2025

What’s going on with global temperatures? Why do we see different patterns at different times?

What is the pattern since 1880? How is it different from what your group observed?

Temperature varies on yearly, decadal, and longer timescales

Slope 0.007°/yr; temperature increasing.007°C per year since 1880

Slope has increased in recent years Trend since 1950

Trend since 1970

Trend since 1950 Trend since 1970 Trend since 2010

Earth’s Thermostat Understanding Earth’s Energy Balance and the Atmosphere

Earth’s average surface temperature has warmed by 0.8°C since measurements began in 1880, and most of the warming has been in the last 30 years

Over the next two weeks, we will explore: What factors control earth’s energy balance How changes to this balance affect the rest of the earth system (e.g. temperature, atmosphere)

What factors do you think are important for determining earth’s surface temperature? Let’s build a conceptual model – a framework of the factors that are important in controlling surface temperature

On Earth, energy is transmitted via: Conduction (direct transfer of heat between two objects of different temperature) Convection (movement of a fluid, such as air or water, in response to a temperature & density difference) Conduction and radiation Convection

On Earth, energy is transmitted via: Conduction (direct transfer of heat between two objects of different temperature) Convection (movement of a fluid, such as air or water, in response to a temperature & density difference) Electromagnetic radiation (flow of energy through space in the form of waves) Outer space contains very few molecules, so only electromagnetic radiation can transmit the Sun’s energy to Earth

Radiation is classified by its wavelength Only a small portion of the spectrum is visible Often divided into shortwave (UV, visible, and near- infrared) and longwave (mid- and far-infrared)

Blackbody radiation describes how a perfectly absorbing object (like a star) absorbs & emits radiation All objects emit radiation according to the Stefan- Boltzmann law: Energy Flux = σ T 4 Objects emit at all wavelengths; the peak wavelength depends on Wien’s Law: λ peak =

Use spectrum/blackbody-spectrum_en.html and determine the approximate intensity and peak wavelength for: spectrum/blackbody-spectrum_en.html The Sun A light bulb Earth

What patterns did you see with increasing temperature? Hotter objects release more energy Hotter objects have a shorter peak wavelength The Sun emits primarily in visible; the earth in infrared Sun 5700°K Light bulb 3045°K Earth 300°K

Solar irradiance: amount of solar radiation received by the Earth Measured in watts of energy per square meter ( ) In your group, examine the record of solar irradiance

Part 2: In your group, analyze the solar irradiance data

What patterns are visible in the data?

Do you see a connection between solar irradiance and the long-term temperature pattern?

The earth is in energy balance with the sun Energy out depends on: T (earth’s temperature) Energy in depends on: S (solar irradiance) A (albedo: how much sunlight is reflected) Energy In (from sun) = Energy Out (from earth) Earth’s albedo is 0.3; approximately 30% of incoming radiation is reflected by surface or atmosphere

The earth is in energy balance with the sun Energy out depends on: T (earth’s temperature, K) Energy in depends on: S (solar irradiance, ) A (albedo: how much sunlight is reflected, unitless) Energy In (from sun) = Energy Out (from earth) So what is Earth’s surface temperature? T earth (in K) = 45.8 x What do you think would happen to T earth if… Earth’s albedo increased? Solar irradiance decreased?

Homework for next class: find Earth’s effective temperature T earth = 45.8 x We already know albedo: A = 0.3, so the equation can be simplified to: T earth = 41.9 x For next class, use your estimate of average solar irradiance to calculate Earth’s effective temperature in K, then convert your answer to °C, and °F