Climate Change and Ozone LossPresentation Transcript
Shohail Motahir Choudhury G. Tyler Miller’s Living in the Environment 14th Edition Chapter 21 Climate Change and Ozone Loss
Key Concepts Changes in Earth’s climate over time Factors affecting climate Possible effects of global warming Adapting to climate change Human impacts on the ozone layer Protecting and restoring the ozone layer
Past Climate Changes Past global temperatures Recent trends in global temperatures
Temperature and climate have been changing throughout the earth’s history.
Climate shifts have occurred due to volcanic emissions changes in solar input , continents moving on shifting plates , meteor strikes, and other factors.
Alternating cycles of freezing and thawing are known as glacial and interglacial periods .
Past Climate Changes
Antarctic ice cores indicate the current interglacial period could last another 15,000 years.
Direct temperature records go back to 1861.
The Intergovernmental Panel on Climate Change (IPCC) was formed in 1988 to evaluate possible future climate changes.
The Greenhouse Effect Fig: 6-14
The Earth’s Natural Greenhouse Effect
A natural process called the greenhouse effect warms the lower troposphere and surface.
A large process also takes place at the earth’s surface due to heat absorbed by surface water.
The earth’s average surface temperature is about 15 degrees Celsius.
The two major greenhouse gases are water vapor and carbon dioxide .
Table 21-1 Page 464 Table 21-1 Major Greenhouse Gases from Human Activities Greenhouse Gas Carbon dioxide (CO2) Methane (CH4) Nitrous oxide (N2O) Chlorofluorocarbons (CFCs)* Hydrochloro- fluorocarbons (HCFCs) Hydrofluorocarbons (HFCs) Halons Carbon tetrachloride Average Time in the Troposphere 100–120 years 12–18 years 114–120 years 11–20 years (65–110 years in stratosphere) 9–390 15–390 65 42 Human Sources Fossil fuel burning, especially coal (70–75%), deforestation, and plant burning Rice paddies, guts of cattle and termites, landfills, coal production, coal seams, and natural gas leaks from oil and gas production and pipelines Fossil fuel burning, fertilizers, livestock wastes, and nylon production Air conditioners, refrigerators, plastic foams Air conditioners, refrigerators, plastic foams Air conditioners, refrigerators, plastic foams Fire extinguishers Cleaning solvent Relative Warming Potential (compared to CO 2 ) 1 23 296 900–8,300 470–2,000 130–12,700 5,500 1,400
Climate Change and Human Activities Increased use of fossil fuels Deforestation Global warming Melting icecaps and glaciers Rising sea level
Climate Change and Human Activities
Humans have increased levels of greenhouse gases in the troposphere by use of fossil fuels , farming, use of inorganic fertilizers, burning forests , etc.
Greenhouse gases are at higher levels than in the past 160,000 years.
Burning of fossil fuels has generated much of the CO2 increase.
Deforestation and clearing grasslands release CO2 and N2O.
Increased cattle raising, and other livestock, has added methane release.
Use of inorganic fertilizers in rice cultivation releases N2O into the troposphere.
USA and Greenhouse Gases
The United States releases more greenhouse gases per person than any other country.
With about 4.6% of the world’s population, the U.S. produces about 24% of the total global emissions.
The U.S. also emits large quantities of CH4 with most coming from landfills, domestic livestock, natural gas, and oil and coal mining.
Evidence of Earth’s Warming
Five findings of the IPCC :
The 20th century was the hottest century in the past 1,000 years.
Since 1861, the average global temperature has risen 0.6 degrees centigrade , with the most increase occurring since 1980.
The 16 warmest years have occurred since 1980.
Glaciers and floating sea ice in some parts of the world are melting and shrinking.
The world’s average sea level rose by 0.1–0.2 meter (4–8 inches).
Global warming refers to temperature increases in the troposphere, which can cause climate change.
Global climate change is a broader term that refers to changes in any aspects of the earth’s climate.
Classroom Activity: Why snow-melting is damaging for the world climate? 2 min.
Oceans 5% Bare sand 30–60% Grass 15–25% Figure: The Albedo or reflectivity of the incoming solar energy. Clouds 50–55% Snow 80–90% City 10–15% Forest 5%
Factors Affecting the Earth’s Temperature Changes in solar output Changes in Earth’s albedo Moderating effect of oceans Clouds and water vapor Air pollution
Today’s sea level Years before present Present 250,000 200,000 150,000 100,000 50,000 0 – 130 0 – 426 0 Height above or below present sea level (meters) Height above or below present sea level (feet)
Troposphere Aerosols Greenhouse gases Warming from decrease Cooling from increase CO 2 removal by plants and soil organisms CO 2 emissions from land cleaning, fires, and decay Heat and CO 2 removal Heat and CO 2 emissions Ice and snow cover Natural and human emissions Land and soil Shallow ocean Long-term storage Deep ocean
Antarctica Greenland Greenland
Some Possible Effects of a Warmer World
Possible Benefits from a Warmer Atmosphere
Less severe winters
More precipitation in some dry areas
Less precipitation in some wet areas
Increased food production in some areas
Expanded population and ranges of some species
Solutions: Dealing with the Threat
Scientists debate the causes, how rapidly the changes might occur, the effects on humans and ecosystems, and the responses that should be taken.
Economists and policymakers disagree on whether:
economic costs of reducing greenhouse gas emissions are higher than the economic benefits;
developed countries, developing countries, or both should take responsibility for reducing greenhouse gases; and
actions to reduce greenhouse gas emissions should be voluntary or required.
Four schools of thought have emerged from this controversy.
Solutions: Dealing with the Threat Options Do nothing Do more research Act now to reduce risks Precautionary principle
Tree plantation Coal power plant Tanker delivers CO 2 from plant to rig Oil rig Crop field Switchgrass Spent oil reservoir is used for CO 2 deposit CO 2 is pumped down to reservoir through abandoned oil field Abandoned oil field CO 2 is pumped down from rig for deep ocean disposal = CO 2 deposit = CO 2 pumping Removing CO 2 from the Atmosphere
Reducing CO 2 Emissions What Can You Do?
Drive a fuel-efficient car, walk, bike, carpool,
and use mass transit
Use energy-efficient windows
Use energy-efficient appliances and lights
Heavily insulate your house and seal all drafts
Reduce garbage by recycling and reuse
Insulate hot water heater
Use compact fluorescent bulbs
Plant trees to shade your house during summer
Set water heater no higher than 49°C (120°F)
Wash laundry in warm or cold water
Use low-flow shower head
Figure 21-20 Page 483
What is Being Done to Reduce Greenhouse Gas Emissions?
The Kyoto Protocol, developed in 1997, would require 39 developed countries to cut emissions of some gases by about 5.2% below 1990 levels by 2012.
Developing countries would not have to make cuts until a later date.
By mid-2004, it had been ratified by more than 120 countries.
In 2001, President George W. Bush withdrew the U.S. from the Kyoto Protocol.
Scott Barnett, an expert on environmental treaties, believes the Kyoto Protocol is a badly thought out agreement and it will not work.
Many countries, companies, cities, states, and provinces are reducing greenhouse gas emissions , improving energy efficiency, and increasing their use of carbon-free renewable energy.
Great Britain reduced its CO2 emissions to its 1990 level by the year 2000, well ahead of the Kyoto target goal.
China reduced it CO2 emissions by 17% between 1997 and 2000 by phasing out coal subsidies, shutting down inefficient coal-fired electric plants, and restructuring its economy toward use of renewable energy resources.
Some major global companies have established targets to reduce their greenhouse gas emissions by 10–65% from 1990 levels by 2010.
Estimates are that current emissions of greenhouse gases must be cut by at least 50% by 2018 to stabilize concentrations at their present levels.
Loss of the Ozone Layer: Reasons for Concern Increased incidence and severity of sunburn Increase in eye cataracts Increased incidence of skin cancer Immune system suppression Increase in acid deposition Lower crop yields and decline in productivity
Long-lived chemicals and ozone level
The first chlorofluorocarbon (CFC) was discovered in 1930. Many use, became very popular and dream chemicals.
2. In 1974, chemists Rowland and Molina found that CFCs were lowering the average concentration of ozone in the stratosphere.
3. Four major conclusions from their research:
a. CFCs remain in the atmosphere because they are insoluble in water and chemically unreactive.
b. Over 11–20 years, these chemicals are lifted into the stratosphere, mostly by convection currents and turbulent mixing of air.
c. CFC molecules break down under the influence of high-energy UV radiation. Chlorine is released and is highly reactive. Fluorine, bromine, and iodine are also released. This causes ozone to be broken down faster than it is formed.
d. These CFC molecules can last in the stratosphere for 65–385 years.
4. In 1988, after 14 years of delay tactics, the CFC industry acknowledged and agreed to stop manufacturing them.
5. Rowland and Molina received the Nobel Prize in chemistry for their work. (1995).
Seasonal Ozone Layer Thinning at the Poles During four months of each year, up to half of the ozone in the stratosphere over Antarctica is depleted. Ozone loss is often called the ozone hole, but it is actually ozone thinning. The total area of stratosphere that suffers from ozone thinning varies from year to year. In 2003, the area was the second largest ever. The primary culprits are CFCs and other ODCs.
The polar vortex is a swirling mass of very cold air that is isolated from the rest of the atmosphere for several months.
Ice crystals in this mass collect CFCs and other chemicals and set up conditions for formation of CIO, the molecule most responsible for seasonal loss of ozone.
As sunlight returns to Antarctica in October, the light stimulates CIO molecules and within a matter of weeks the ozone is reduced by 40–50% on average.
It is predicted that the worst ozone thinning will be between 2010 and 2019.
Increased UV radiation reaching the earth’s surface from ozone depletion is harmful to human health, crops, forests, animals, and materials. Figure 21-24 lists the effects of ozone depletion.
Exposure to UV radiation is a major cause of skin cancers.