GEOG 2050 CH.7 The Changing Climate Flashcards

Flashcards for Chapter 7 of Geography of the Atmosphere (The Changing Climate)

Climate

• Long-term average of weather and the average frequency of extreme weather events

  • Average temperature, precipitation, wind, and humidity represent the climate of a given region

Weather

• State of atmosphere at any given moment

  • Sunshine, rain showers, heat waves, thunderstorms, and clouds

Parts of the Climate System

• Climate results from interaction between atmosphere, biosphere, lithosphere, hydrosphere, and cryosphere

• Energy and matter move through Earth’s systems and form the climate system

Temperature Increases and Climate Change

• Since 1880, average temperature of the lower atmosphere has increased 0.8°C (1.5°F)

• Climate change occurs when long-term average of any meteorological variable (ex temperature of precipitation) changes

• Individual extreme weather events do not change long-term average

Climate Forcing Factor

• A force that can change climate and is unaffected by the climate system (ex solar forcing or volcanic forcing)

Climate Feedback

• Enhances or diminishes climate change that has already been set in motion (ex ice-albedo feedback)

• Ice-Albedo Positive Feedback:

  • Destabilizes the climate system and causes climate change

  • Can also be a negative feedback that stabilizes climate

Modes of Climate Change

• 3 natural modes of climate change:

  • Long-term trends

  • Repeating cycles

  • Random anomalies

• These changes are caused by climate forcing factors and climate feedback

The Cenozoic Cooling Trend

• 55 million years ago, average global temperature was about 12°C (22°F) warmer than  today

• No ice at either pole and atmospheric CO2 concentrations above 1,000 ppm (roughly 400 ppm at present)

• Building and uplift of Tibetan Plateau and Himalayas are leading explanation for Cenozoic cooling trend

Climate Cycles: A Climate Roller Coaster

• During the last 2.6 million years (Quaternary Period) climate has cycled between cold glacial and warm interglacial 22 times

• In last million years, glacial have lasted about 90,000 years, followed by interglacial that lasted about 10,000 years

• Current interglacial, called Holocene, with unusually stable climate began 10,000 years ago

Milankovitch Cycles

• Small changes in Earth-Sun orbital geometry that resulted in Quaternary glacial-interglacial cycles

• Internal feedbacks amplify climate changes forced by Milankovitch cycles

• Cycles operate outside of, and are unaffected by climate system - a climate forcing factor (orbital forcing)

Climate Anomalies

• Occur randomly (ex changes in Sun’s output, changes in ocean conveyor belt, and volcanic eruptions)

Sunspot Cycles

• Low sunspot activity may have triggered Little Ice Age

• High sunspot activity may have triggered Medieval Warm Period

• Caused by climate forcings and feedbacks different from those that drive longer-term climate patterns

The Younger Dryas

• Cold period in much of Northern Hemisphere between 12,900 and 11,600 years ago

Ocean Conveyor Belt

• Global system of surface and deep ocean currents that transfers heat toward the poles

  • Ocean conveyor belt system likely greatly slowed or shut down entirely due to melting of Laurentide ice sheet - frigid Younger Dryas climate

Reconstructing Past Climates

• Paleoclimatologists reconstruct Earth’s past climates

• Past climates are recorded in various natural materials (ex tree rings, glaciers, cave deposits, and ocean sediments

Long-Term Carbon Cycle

• Carbon is removed from atmosphere, oceans, and biosphere and stores for millions of years in the lithosphere in long-term carbon cycle

  • Carbon is moved through weathering and erosion and through burial and preservation of photosynthetic organisms

  • Carbon leaves lithosphere through volcanic eruptions and through burning of fossil fuels

Short-Term Carbon Cycle

• Carbon moves relatively quickly among atmosphere, biosphere, and oceans in short-term carbon cycle

  • Most carbon in the short-term cycle resides in the oceans

Human Activity and Carbon Cycling

• People have greatly accelerated the transfer of carbon from the lithosphere to the atmosphere (about 35 billion metric tons each year)

• Burning of fossil fuels and deforestation are leading causes of this acceleration

Anthropogenic Greenhouse Effect

• Human activities have cause atmospheric CO2 concentrations to rise over 400 ppm

• Current rate of increase is 2.5 ppm per year

• Possibly as a result, atmospheric temperatures are rising

• Human emissions of CO2 and other greenhouse gases are creating an anthropogenic greenhouse effect (enhancement of the natural greenhouse effect) that is changing in the atmosphere

• Ice-albedo positive feedback is warming the Arctic at about twice the rate of the rest of the world

The Keeling CurveEarth’s average atmospheric temperature is higher now than at any time in the last 1,500 years

• No known natural climate forcing factor can explain the current warming trend

• Graph showing the change in atmospheric CO2 concentrations since 1958

• Before 1800, CO2 concentrations were much lower than today

• Atmospheric CO2 concentrations and temperature have risen and fallen together over last 800,000 years

Comparing today with the last 800,000 years

• Earth’s average atmospheric temperature is higher now than at any time in the last 1,500 years

• No known natural climate forcing factor can explain the current warming trend

Climate Projections

• Climate change projections vary depending on assumptions about how much carbon dioxide will be emitted

Earth System Model

• Mathematical simulation of the behavior of the atmosphere, oceans, and biosphere that can be used to create long-term climate projections

500 ppm goal

• Most climate scientists conclude that limiting atmospheric CO2 to less than 500 ppm could avoid significant climate change

• Atmospheric CO2 annual emissions must be cut by almost 80% in the next few decades

How to Reduce Carbon

• We must make international, national, and local changes:

  • Doubling the efficiency of cars

  • Increased use of carbon-free energy

  • Carbon taxes

  • Different personal choices

Carbon Foorprint

• Amount of greenhouse gases (particularly CO2) any activity generates

  • Almost all of our daily activities rely on energy from fossil fuels and emit CO2 into the atmosphere