Global Climate Change

Past Climate Change

• Large climate changes have occurred in the past– Eruptions of various volcanoes, including Mount

Pinatubo in 1991 alter the climate by sending a cloud of gas and ash high into the atmosphere

• Initial cooling due to interference of light from particles in the atmosphere

• Followed by warming period• These changes were observed after the volcanic

explosion of 1991

• Many different models have shown that global temperatures are likely to rise several degrees this century– Will have many different effects on humans and

ecosystems

Natural Climate Change• Main alterations in the climate

come from volcanic eruptions, changes in solar input, moving continents, meteor strikes, and other factors

• Over the past 1,000 years, the Earth has experienced fairly stable temperatures, with a rise becoming noticeable during the last century

• Major hypotheses about changing climate:– Change in the Earth’s elliptical orbit about

every 100,000 years– Change due to tilt on Earth’s axis every

40,000 years– Ice ages could have been caused by

wobbling of Earth on its axis (every 26,000 years)

– 11-year sunspot cycles and 22-year solar magnetic cycles

PAST CLIMATE AND THE GREENHOUSE EFFECT

Figure 20-2Figure 20-2

Analyzing Past Climate• According to measurements of

carbon dioxide and other gases in ice core samples, changes in troposphere levels of CO2 correlate fairly closely with variations in the average global temperature during the past 160,000 years– This demonstrates that CO2 has a

direct effect on global temperature• In 2005, an ice core showed that

CO2 levels in the troposphere are the highest they have been in 650,000 years

• May 9, 2013 – 400 ppm milestone!

The Natural Greenhouse Effect• Three major factors shape Earth’s climate

1. The sun2. The natural greenhouse effect: greenhouse gases in the

atmosphere warm the surface and lower troposphere-Chemist Svente Arrhenius first recognized in 1896-Four major greenhouse gases are water vapor, carbon dioxide, methane (CH4), and

nitrous oxide (N2O)-These gases have always been present in the troposphere in varying

concentrations-Fluctuations in these concentrations (along with changes in solar output) are the

major cause of changes in tropospheric temperature over the past 400,000 years

3. Ocean cycles and natural cooling processes-oceans store carbon dioxide and heat-Evaporate and receive water as part of the hydrologic cycle-Move stored heat around the globe through currents-natural cooling process occurs as heat causes water to evaporate from the surface of the ocean, condensing and forming droplets in clouds and releasing their stored heat higher in the atmosphere

Climate Change and Human Activities• The basics: the idea is that a variety of human

activities, most notably burning fossil fuels, increases the concentration of gases like carbon dioxide (which trap and hold solar heat and cause an increase in surface temperature) to such an extent that the entire climate of the planet can be affected

• Since the beginning of the Industrial Revolution (about 275 years ago), human actions have lead to a major increase in three of the greenhouse gases (CO2, CH4, and N2O)– Burning fossil fuels adds CO2 and CH4

– Clearing and burning forests adds CO2 and N2O– Planting rice and using inorganic fertilizers releases N2O

• Plants emit 10-30% of the greenhouse gases present in the atmosphere, but since this has been going on for hundreds of thousands of years, it cannot be responsible for the current drastic increase in global temperatures

Global GHG Emissions• United States has 4% of the world’s population

and emits 25% of its anthropogenic carbon dioxide (22% of total GHG emissions)– China emits 14%, EU 13%, Russia 6%, Japan 5%,

and India 4%– China’s emissions increased 88% between 1990 and

2004; U.S. emissions rose 19% during that same period.

• China’s total emissions are expected to surpass U.S. by 2025 due to increasing population and coal burning; increased vehicle use and ownership

• Other developing countries will likely follow• U.S has not signed onto Kyoto protocol; China and India are

not required to reduce their emissions due to economic and growth status

• Still, average American releases 10 times as much CO2 as average Chinese person

• Per capita emissions in E.U. and Japan are about half of those for Americans

Climate Change and Human Activities

• Humans have been emitting CO2 and CH4 from agriculture for over 11,000 years

The IPCC

• 1988: U.N. forms the Intergovernmental Panel on Climate Change (IPCC) to document past and current climate changes and to predict future trends

– Includes 2000 climate experts from 70 countries– Their report, which was a compilation of 12 years worth of study,

was that there is a 90-99% probability that the troposphere is warming

– “There is new and stronger evidence that most of the warming that has occurred over the last 50 years is attributable to human activities.”

– Has published 4 reports since then, the next one is due in October, 2014

• Major findings of the reports published by the IPCC:– 90-99% confidence that the Earth is the hottest it has been in 400

years and 66-89% confident that it is hotter than it has been in the past 1,000 years

– Since 1900, the average global temperature has risen 0.6 C (1.1 F) over the entire globe and 0.8 C (1.4 F) over the continents

• Most of this increase has taken place since 1980– 10 warmest years since 1861 have occurred since 1990 (top five

hottest: 2010, 2005, 1998, 2003 & 13 (tie), 2002, 2006, 2009, 7, 4 12 (all tie)

– Arctic temperatures have risen almost twice as fast as the rest of the world over the last 50 years

– Glaciers and sea ice melting and shrinking at increasing rates– Warmer temperatures in Alaska and Russia are causing melting of

permafrost, which releases carbon dioxide and methane– During the last century, the average sea level has risen by 4-8

inches• Due to thermal expansion and melting glaciers/land-based ice

The Critics

• Healthy skepticism is good- it’s an important part of the scientific process

• Some scientists have legitimate concerns about the “consensus” and particulars of climate change theory, and point to incomplete data on some projections. This is valid.

• Others are industry-funded groups that have a financial interest in preventing regulatory action on climate change

The Response• Although many sources claim that there is no

“consensus on global warming,” the following was signed onto by the national science foundations of Brazil, Canada, China, France, Germany, India, Italy, Japan, Russia, the United Kingdom and the United States:– The atmospheric concentration of carbon dioxide is the

highest it has been in the period of time as far back as reliable measurements can be made (400,000 years)

• Have increased from 280 ppm in 1750 to 400 ppm in 2013– The planet will, with a 90-99% degree of certainty,

experience an average surface temperature increase of 1.5-4.8°C by 2100

– Due to developing economies and population increases, global energy demand is expected to increase 60% in the next 25 years

• Fossil fuels are expected to provide 85% of this demand– Cost-effective and long-lasting solutions need to be taken

to address the clear anthropogenic effects on the global climate

Scientific Modeling and Consensus

• Mathematical models used to project the effects of increasing ghg concentrations on global temperatures and climate systems– Coupled general circulation models

(CGCMs) take into account sunlight, clouds, land masses, oceans and their currents, concentrations of ghg and pollutants, and positive and negative feedback loop systems

Sun

Stepped Art

Aerosols

Greenhousegases

Warmingfrom

decrease

Cooling from

increase

CO2 removal by plants and

soil organisms

CO2 emissions from land

cleaning, fires, and decay

Heat andCO2 removal

Heat andCO2 emissions

Ice and snow cover

Natural and human emissions

Land and soil biotoa

Long-termstorage

Deep ocean

Shallow ocean

Troposphere

Fig. 20-6, p. 469

The Scientific Consensus about Future Climate Change

• Measured and projected changes in the average temperature of the atmosphere.

• 90-99% probability that Earth’s temperature will increase by 2.4-5.4 C (4.5-9.7 F) by 2100– IPCC, U.S. National

Academy of Sciences, American Geophysical Union have reached similar projections

Global Climate Change• There is a difference between “global warming”

and “global climate change”• Global warming: the temperature increase in the

troposphere, which can cause global climate change– Global climate change refers to the changes in any

aspects of the earth’s climate, including temperature, rainfall and other precipitation patterns, storm intensity, and desertification/biome shift

• Scale of problem of increase in troposphere temperature also dependent on how fast it occurs– Worst-case scenario: it is too late to reverse climate

change, and eventually ecosystems will collapse, low-lying cities will flood, forests will be consumed in fires, grasslands will become deserts, wildlife will disappear, coastal storms will wipe out cities, tropical diseases will become pandemics

• Referred to as the tipping-point- have we passed it?

Factors Affecting Climate

-Climate feedback systems• Positive feedback systems can amplify

(increase) changes in the tropospheric temperature. These are harmful, and unfortunately more common than negative feedback systems

• Negative feedback systems can decrease changes in the tropospheric temperature. These are corrective.

Climate Factors: Oceans

• Oceans moderate Earth’s temperature by storing heat and removing almost half of the excess carbon dioxide human activities release into the atmosphere

Climate Factors: Clouds

• This is a major unknown factor, because clouds could either warm or cool the troposphere

• What is known is that warmer temperatures will cause an increase in could formation – Could cause warming effect (positive

feedback) by absorbing and releasing heat into the troposphere

– Could cause cooling effect (negative feedback) by reflecting more sunlight back into space

– Could also decrease surface warming by reflecting and blocking more sunlight

Climate Factors: Outdoor Air Pollution

• Aerosol pollutants and soot produced by human activities can warm or cool the atmosphere, but such effects will decrease with any decline in outdoor air pollution– Aerosols are microscopic

droplets and solid particles of various air pollutants

Other Climate Effects• Effects of higher carbon dioxide levels on

photosynthesis: larger amounts of carbon dioxide could actually increase the process of photosynthesis, eventually leading to a drop in carbon dioxide as plants absorb it at a higher rate

• Effects of a warmer troposphere on methane emissions: warmer air can release methane stored in bogs, wetlands, and tundra soils to accelerate global warming– Since methane has a low boiling point, a small increase

in temperature can release it– Methane is 25 times more potent as a greenhouse gas

than carbon dioxide– Large stores of methane are locked in wetlands and as

icy methane hydrates under permafrost, but will be released as ice melts

Effects of Global Warming

• In general: some areas will benefit because of less severe winters, more precipitation in dry areas, less precipitation in wet areas, and increased food production; but other areas will benefit due to excessive heat, lack of water, and decreased food production– According to the IPCC, poor people and

wildlife species will suffer the most (as usual)

– Most climate changes are too complex to predict what will happen to a specific area; only general trends can be predicted

Rising Sea Levels

• Sea levels rise and fall naturally• IPCC: world’s sea level will rise 4-35

inches (9-88 cm) over the next century (90-99% probability)

Changing Ocean Currents

• Ocean currents are extremely important to Earth’s climate– Move carbon dioxide and heat to and from the deep

sea– Transfer hot and cold water between the tropics and

the poles– Cycle works because water in the North Atlantic is

saltier and more dense due to lower temperature, and creates current

Changes in Precipitation and Weather Extremes

• Climate changes will shift patterns of precipitation by altering the rate and distribution of water in the hydrologic cycle

– Some areas will get more water; others will get less– This will affect where crops can be grown, and increase pressure on

arable land for food production– Severe water shortages in areas already short of water

• Severe weather events will become more intense and frequent

– Droughts will intensify and last longer, causing famine and desertification to increase

• National Center for Atmospheric Science reported that the area of Earth’s surface affected by drought increased from 15% to 30% between the 1970’s and 2002 due to reduced precipitation and higher temperatures

– Heat waves will increase• 2003 heat wave in Europe killed 54,000 people and devastated crop

production

• The hurricane question– No conclusive evidence established, but basic scientific theory

predicts stronger storms due to increased ocean temperatures• Peak intensity and wind duration of average hurricanes increased 50%

between 1970 and 2004

Effects on Biodiversity• Warmer climate could expand ranges and populations

of warm-weather adapted plant and animal species– Includes many weeds, insect pests, and disease-carrying

organisms• 1 million other species could face extinction (UN)

– Specialized niches or narrow temperature tolerance– Most likely to suffer are coral reefs, polar seas, coastal

wetlands, arctic and alpine tundra, mountaintop ecosystems

– Increased incidence of forest fires (also increases carbon dioxide)

• Agriculture and fish stocks could also be affected– Climate shifts and hydrologic cycle changes could

completely disrupt human agricultural system• Rice-producing areas flooded• Northward shift of ideal food-growing climate from

Midwestern U.S. to Canada, where soils are far less fertile

• Decreased snow mass would cause a sharp decline in China and India, due to reduction of irrigation water from Yangtze River (which is fed by summer melt from the Himalayas)

Effects on People

• Heat stress will become more frequent and prolonged– Increase death and illness, especially among

older people and urban poor• Fewer people will die from cold weather (more

people typically die from cold than heat)• Incidences of tropical infectious diseases like

malaria, yellow fever, and dengue fever will rise– Could increase death rate in sub-Saharan Africa

from tropical diseases to 185 million people by the end of the century

• Flooding of coastal areas will lead to mass displacement of people

Dealing With Global Warming: Solutions

• Two basic strategies for dealing with global warming:– Mitigation: reducing greenhouse gas emissions,

learning more about the global climate and shift to non-carbon energy options

– Adaptation: recognizing global warming as inevitable and devise strategies to reduce its harmful effects

– Most think a mix of both approaches is needed• Reducing the threat of global warming

(mitigation):– Improve energy efficiency, rely on carbon-free

renewable energy resources, find ways to keep anthropogenic carbon dioxide out of the atmosphere

• Strategies would all be enhanced by reducing population and reducing poverty

Carbon Sequestration• Carbon sequestration is the process of capturing

and storing carbon dioxide emissions• Many different methods available:

– Planting trees that sequester and remove atmospheric carbon dioxide

– Soil sequestration- plants such as switchgrass can remove carbon dioxide from the air and store it in the soil

– Reducing emissions of carbon dioxide and nitrous oxide from the soil- use no-till cultivation and set aside depleted crop fields

– Remove carbon dioxide from smokestacks- carbon dioxide is pumped deep underground or injected deep into the ocean

• Problems: expensive, limited amount of carbon dioxide can be removed, would increase cost of electricity, could upset global carbon cycle and deep-sea life

Fig. 20-14, p. 481

Cut fossil fuel use (especially coal)

Shift from coal to natural gas

Improve energy efficiency

Shift to renewable energy resources

Transfer energy efficiency and renewable energy technologies to developing countries

Reduce deforestation

Use more sustainableagriculture and forestry

Limit urban sprawl

Reduce poverty

Slow population growth

Remove CO2 from smoke stack and vehicle emissions

Store (sequester)CO2 by planting trees

Sequester CO2 deep underground

Sequester CO2 in soil by using no-till cultivation and taking cropland out of production

Sequester CO2 in the deep ocean

Repair leaky natural gas pipelines and facilities

Use animal feeds that reduce CH4 emissions by belching cows

Solutions

Global Warming

Prevention Cleanup

Government Role in Reducing Climate Change• Could reduce using three major methods:

– Carbon taxes/energy taxes- taxes on each unit of carbon dioxide emitted by fossil fuels or each unit of fossil fuel burned

• Could offset cost by decreasing taxes on income, labor, and profits

– Level economic playing field- greatly increase government subsidies for energy-efficient technologies, carbon-free renewable energy technologies, carbon sequestration, and sustainable agriculture

• Reduce subsidies and tax-breaks for non-renewable energy– Technology transfer- governments of developed countries

give renewable-energy technology to developing countries• U.N. Environment Program- projected global warming will cost

the world economy more than $300 million annually by 2050– Implementing strategies might cost more in the short-term,

but would cost less in the long-term dealing with harmful effects

• Critics of plans say taking measures to combat global climate change will hurt the economy too much to be useful– Problems: do not take into account savings from using

renewable energy sources, underestimate ability of marketplace to respond to economic initiatives, underestimate potential costs of disasters and disease from climate change

The Kyoto Protocol• 1997: First negotiations of international legislation to reduce

greenhouse gas emissions took place in Kyoto, Japan– 2,200 delegates from 161 countries– Drafted the Kyoto Protocol, a resolution to cut emissions of

methane, nitrous oxide, and carbon dioxide by 5.2% of their average levels (by country) by 2012

– 38 countries initially signed on– Developing countries excluded because reducing emissions

might curb growth– 2005: Phase 2 negotiations for after 2012

• Protocol allows for “carbon trading,” which gives credits to countries that reduce their emissions

– Can then use credits to avoid reducing emissions in other areas, save for future use, or sell to other countries

• U.S. did not sign onto Kyoto Protocol, citing harm to the U.S. economy and exclusion of developing countries that have high emissions (China, India, Brazil)

• U.S. and Australia the only two “first world” countries that have not signed on, although the U.S. in particular could use its technology and leadership to set an excellent example in progressive climate change action

Beyond Kyoto• Some believe excluding high-emissions developing countries will make the Kyoto

Protocol ineffective– Call for new treaty, including emissions trading program, that includes those

countries– Or other, faster and more drastic alternatives

• Many countries, states, cities, businesses, schools, and individuals are taking their own actions

– EU to increase use of renewable energy and cut energy use by 20% by 2020– Japan to lead technological development of extremely energy-efficient

appliances– Canada closing coal-burning power plants– Chinese phasing out coal subsidies, shutting down inefficient plants, and

increasing energy efficiency and use of renewable energy– California has goal of reducing ghg emissions to pre-1990 levels by 2020 and to

80% below 1990 levels by 2050– Half of U.S. states have climate action programs– Many companies setting goals for reducing emissions

• Including oil companies (BP spent $20 million to reduce ghg emissions to 1990 levels and saved $250 million, 32 times original investment)

• GE, Shell, Duke Energy, Wal-Mart pushed for Congress to regulate carbon dioxide and impose mandatory emissions caps

Think Globally, Act Locally• Ways to for businesses, schools, and individuals to

reduce emissions – 25 Pennsylvania colleges joined to purchase wind power for

use on campuses– Building energy-efficient new buildings and renovating old

ones– Drive fuel-efficient cars, or walk, bike, carpool, or use mass

transit– Use energy-efficient windows, appliances, lights, and

insulation– Reduce garbage by recycling and reuse– Insulate hot water heater and set no higher than 120°F/49°C– Plant trees to shade house during summer– Wash laundry in warm or cold water– Use low-flow showerhead– Buy products from companies that are trying to reduce their

climate impact– Demand that the government make climate change a priority

Preparing for Climate Change

• The world would need a 60% cut in emissions of ghg to stabilize their concentrations in the troposphere by 2050

• Wise to have some preparation (adaptation strategy)– Connect wildlife reserves with corridors– Move hazardous materials storage tanks away

from the coast– Expand existing wildlife reserves toward poles– Stockpile supply of key foods– Prohibit new construction in low-lying coastal

areas– Waste less water, and develop crops that need

less water