Chapter 21 Global Climate Change

Overview of Chapter 21 Introduction to Climate Change Causes of Global Climate Change Effects of Climate Change Melting Ice and Rising Sea Level Changes in Precipitation Patterns Effects on Organisms Effects on Human Health Effects on Agriculture Dealing with Global Climate Change

Introduction to Climate Change- Mean Annual Global Temperature 1960-2005

Climate Change Terminology Greenhouse Gas absorbs infrared radiation Ex: Carbon dioxide, methane, nitrous oxide, chlorofluorocarbons and tropospheric ozone Positive Feedback change triggers a response that intensifies the changed condition Infrared Radiation has a wavelength longer than visible light, but shorter than radio waves Greenhouse Effect increase of heat in a system where energy enters (often as light), is absorbed as heat, and released sometime later

Introduction to Climate Change Evidence for Climate Change 11 of the 12 years between 1995 and 2006 were among the twelve warmest years since the mid-1800s Phenological spring in N. hemisphere now comes 6 days earlier Warming is not due to natural causes

Causes of Climate Change Increased concentration of CO2 (right) Burning fossil fuels in cars, industry, and homes Deforestation Burning of forests

How Do We Know What Temperatures Were in the Past? Scientists analyze tiny air bubbles trapped in ice cores learn about past: troposphere composition. temperature trends. greenhouse gas concentrations. solar, snowfall, and forest fire activity. Figure 20-3

How Do We Know What Temperatures Were in the Past? 2005 ice core showed that CO2 levels in the troposphere are the highest they have been in 650,000 years. Figure 20-4

The Natural Greenhouse Effect major factors shape climate: The sun. Greenhouse effect that warms the earth’s lower troposphere and surface because of the presence of greenhouse gases. Oceans store CO2 and heat, evaporate and receive water, move stored heat to other parts of the world. Natural cooling process through water vapor in the troposphere (heat rises).

Major Greenhouse Gases The major greenhouse gases in the lower atmosphere are water vapor, carbon dioxide, methane, and nitrous oxide. Gasses have always been present Fluctuations in these gases, plus changes in solar output are the major factors causing the changes in tropospheric temperature over the past 400,000 years.

Major Greenhouse Gases Increases in average concentrations of three greenhouse gases in the troposphere between 1860 and 2004, mostly due to fossil fuel burning, deforestation, and agriculture. Figure 20-5

CLIMATE CHANGE AND HUMAN ACTIVITIES Evidence earth’s troposphere is warming, mostly because of human actions: The 20th century was hottest century in past 1000 years. Since 1900, the earth’s average tropospheric temperature up 0.6 C°. Past 50 years: Arctic temperatures have risen almost twice as fast as those in the rest of the world. Glaciers and floating sea ice are melting and shrinking at increasing rates.

CLIMATE CHANGE AND HUMAN ACTIVITIES melting permafrost releases more CO2 and CH4 in the last century, the world’s sea level rose by 10-20 cm, runoff from melting and land-based ice expansion of ocean water as temperatures rise.

Effects of Global Climate Change- Melting Ice and Rising Sea Levels Sea level rise caused in 2 ways Thermal Expansion Water expands as it warms Melting of land ice Retreat of glacier and thinning of ice at the poles Melting has positive feedback Increased melting decreases ice, which decreases albedo leading to further warming

Other Pollutants Cool the Atmosphere Atmospheric Aerosols tend to cool the atmosphere Both human and natural sources Tiny particles that remain in troposphere for weeks or months Contain many chemicals, but often contain sulfur Complicates models of climate change

The Scientific Consensus about Future Climate Change There is strong evidence that human activities will play an important role in changing the earth’s climate during this century. Coupled General Circulation Models (CGCMs) combine, the effects of the atmosphere and the oceans on climate.

by plants and soil organisms (Cooling effect) Sun Troposphere Cooling from increase Heat and CO2 removal (Cooling effect) Green- house gases Heat and CO2 emissions Cooling from Aerosols CO2 removal by plants and soil organisms (Cooling effect) CO2 emissions from land clearing, fires, and decay Warming from decrease Ice and snow cover Shallow ocean Land and soil biota Figure 20.6 Natural capital: simplified model of some major processes that interact to determine the average temperature and greenhouse gas content of the troposphere and thus the earth’s climate. Long-term Storage (Cooling effect) Natural and human emissions Deep ocean Fig. 20-6, p. 469

Melting Ice and Rising Sea Levels 1957 1998

Case-In-Point Impacts in Fragile Areas Eskimo Inuit live traditional life dictated by freezing climate Climate change is altering their existence Wildlife are smaller or displaced Reduced snow cover and shorter river ice seasons Thawing of permafrost (right)

Effects of Global Climate Change- Changing Precipitation Patterns Some areas will get more water, some areas will have greater droughts Ex: Hurricanes will likely get stronger

Effects of Global Climate Change- Effects on Organisms Zooplankton in parts of California Current have decreased by 80% since 1951 Effects entire food chain Decline in krill around Antarctica Decrease in penguin populations Species have shifted their geographic range Migrating birds are returning to summer homes earlier Where’s the food?

Effects on Organisms - Coral Reefs Coral reefs can be bleached (right) due to increase in water temperature Affects coral symbiotes and makes them more susceptible to diseases to which they would otherwise be immune

Effect on Organisms - Vegetation Beech Tree Range

Effects on Human Health Increased number of heat-related illnesses and deaths

Effects on Agriculture Difficult to anticipate Productivity will increase in some areas and decrease in others Rise in sea level will inundate flood plains and river valleys (lush farmland) Effect on pests is unknown Warmer temperatures will decrease soil moisture- requiring more irrigation Location (i.e. elevation and altitude) where certain crops can be grown may have to change

International Implications of Climate Change Developed vs. Developing countries Differing self-interests Differing ability to meet the challenges of climate change

Dealing with Global Climate Change To avoid the worst of climate change, CO2 levels must be stabilized at 550ppm 50% higher than current levels Two ways to attempt to manage climate change Mitigation Focuses on limiting greenhouse gas emissions to moderate global climate change Adaptation Focuses on learning to live with to the environmental changes and societal consequences brought about by global climate change

Dealing with Global Climate Change- Relationship Between Mitigation and Adaptation

Dealing with Global Climate Change- Mitigation Locate/invent alternative fuels to fossil fuels Increase efficiency of cars and trucks Sequestering carbon before it is emitted Plant and Maintain trees to naturally sequester carbon

Dealing with Global Climate Change- Adaptation Rising sea levels and coastal populations Move inland Construct dikes and levees Adapt to shifting agricultural zones NYC sewer line

International Efforts to Reduce Greenhouse Gas Emission Kyoto Protocol Legally binding Provides operational rules on reducing greenhouse gases US and Australia have not signed it- it will be difficult to implement without US backing