19-2 What Are Some Possible Effects of a Warmer Atmosphere?

Concept 19-2 The projected rapid change in the atmosphere's temperature during this century is very likely to increase drought and flooding, shift areas where food can be grown, raise sea levels, result in intense heat waves, and cause the premature extinction of many species.

Important distinction:• Global Warming vs. Climate Change

Global warming = the temperature of the troposphere increasing as a result of an increase in the natural greenhouse effect

Climate change = a broader term referring to any changes in the Earth’s climate as a result of a warmer troposphere

19-2 What Are Some Possible Effects of a Warmer Atmosphere?

Remember: we are not talking about local weather, we are talking about global climate.

A rapid increase in the temperature of the troposphere during this century would give us little time to deal with its harmful effects.

Many scientists fear a “tipping point” after which rapid/severe climate changes cannot be prevented.

Plant/animal distribution and ocean/atmosphere circulations are based on the current global climate.

What if the climate changes??

19-2 What Are Some Possible Effects of a Warmer Atmosphere?

Severe Drought Is Increasing: The Browning of the Earth

Drought accelerates global warming, leads to more droughts• Severe lack of water• Growth of trees and other plants will slow• Less CO2 taken out of atmosphere• Also, more forest and grass fires will add CO2 to the

atmosphere

Groundwater, lakes, and rivers will be depleted because of lack of precip., increased evaporation, and increased need to agricultural irrigation.

Ice and Snow Are Melting

Why will global warming be worse in the polar regions?• Because the ice was reflecting 90% of the sunlight

back into space…when it melts it is replaced by water which absorbs 90% of the sunlight.

• Positive feedback loop

Ice and Snow Are Melting

The world’s sea ice sheets and land-based glaciers are slowly melting.• The loss of ice is happening much faster than

scientists thought possible. Why should we care if snow and ice are melting?• Arctic ice regulates the temperature and precipitation

of regions to the south (North America, Europe)• Mountain glaciers play a vital role in the water cycle

and the availability of fresh water for hundreds of millions of people.• Drinking• Agriculture

Ice and Snow Are Melting

20041948

Ice and Snow Are Melting

Sea Levels Are Rising

Average sea level has been slowly rising and the rate is increasing

• 2/3 of the rise is the from the thermal expansion of warm water

• The remaining 1/3 of the rise is from the melting of land-based ice• Floating ice is already

in the water (buoyancy)

Projected irreversible effect• Degradation and loss of 1/3 of coastal estuaries,

wetlands, and coral reefs• Disruption of coastal fisheries• Flooding of • Low-lying barrier islands and coastal areas• Agricultural lowlands and deltas

• Contamination of freshwater aquifers (groundwater)• Submergence of low-lying islands in the Pacific and

Indian Oceans and the Caribbean

Sea Levels Are Rising

Areas of Florida to flood if average sea level rises by one meter

13% of the world’s urban population lives near sea level

Many cities would be devastated by even relatively small increases in sea level

Sea Levels Are Rising

Permafrost Is Likely to Melt: Another Dangerous Scenario

As arctic temperature increases, permafrost melts and the organic matter in soils and lake bottoms decomposes, releasing CH4

Effect on global warming• Warmer air can release methane gas stored in bogs,

wetlands, and tundra soils and accelerate global warming.

Ocean Currents Are Changing but the Threat Is Unknown

Ocean currents act like large conveyor belts redistributing heat all over the planet.

Global warming can change ocean currents by increasing the temp. of the water, adding large amounts of freshwater from melting ice, and increasing salinity by increasing evaporation.

The temp. of water greatly effects the temp. of the air above it.

Many areas have warmer climates despite their higher latitudes; that will change if the ocean currents change

By altering ocean currents and air circulation, global warming can both excessive warming or cooling.

This will lead to prolonged heat waves and droughts in some areas and prolonged heavy rains and increased flooding in other areas.

Hurricanes and typhoons feed off the warm ocean waters. If these waters are warmer, that means more energy for the storms and stronger storms.

Extreme Weather Will Increase in Some Areas

Habitat loss and ecosystem changes will cause many species to seek new habitats or face extinction.

Specialist species that cannot evolve or migrate fast enough are the most vulnerable.• An estimated 30% of land

plants/animals could go extinct with only a 2ºC temp. increase

Global Warming Is a Major Threat to Biodiversity

Changes in Average Ocean Temperatures, Relative to Coral Bleaching Threshold

Most susceptible ecosystems:• Coral reefs, polar seas, coastal wetlands, alpine and

arctic tundra

Exploding Populations of Mountain Pine Beetles in British Columbia, Canada

Global Warming Is a Major Threat to Biodiversity

Climate Change Will Shift Areas Where Crops Can Be Grown

Regions of farming may shift• Decrease in tropical and subtropical areas• Increase in northern latitudes• However, it will be less productive; soil not as fertile

Loss of productivity could be offset by a longer growing season

Genetically engineered crops developed to be more tolerant to drought and temperature extremes

Global warming will increase human deaths from:• Heat stroke• Increased flooding• Malnutrition and starvation from disruption of food supply• Spread of tropical diseases to temperate regions• More insects, microbes, toxic molds, and fungi• Increase in some forms of air pollution, more O3

• Decreased amount of vital natural capital• Increased number of environmental refugees• Increased poverty

Climate Change Will Threaten the Health of Many People

19-3 What Can We Do to Slow Climate Change?

Concept 19-3A To slow the rate of global warming and climate change, we can increase energy efficiency, sharply reduce greenhouse gas emissions, rely more on renewable energy resources, and slow population growth.

Concept 19-3B Governments can subsidize energy efficiency and renewable energy use, tax greenhouse gas emissions, set up cap-and-trade emission reduction systems, and help to slow population growth.

Climate change is such a difficult problem to deal with because:

• The problem is global• The effects will last a long time• It is a long-term political issue• The harmful and beneficial impacts of climate

change are not spread evenly• Many actions that might reduce the threat are

controversial because they can impact economies and lifestyles

Dealing with Climate Change Is Difficult