Global Climate ChangeGlobal Climate ChangeFindings from the Third Assessment Report (TAR) Findings from the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC)of the Intergovernmental Panel on Climate Change (IPCC)

WarmingWarming

The Climate SystemThe Climate System

Global warmingGlobal warming(temperature increase)(temperature increase)

Effects of global warming on water cycleEffects of global warming on water cycle

Speeds up globalSpeeds up globalwater cyclewater cycle

More extreme weather eventsMore extreme weather events• DroughtsDroughts• StormsStorms• FloodsFloods

HealthWeather-related mortalityInfectious diseasesAir-quality respiratory illnesses

AgricultureCrop yieldsIrrigation demands

Water ResourcesChanges in water supplyWater qualityIncreased competition for water

Coastal AreasErosion of beachesInundation of coastal landsCosts to protect coastal communities

ForestsChange in forest compositionShift geographic range of forestsForest health and productivity

Species and Natural AreasShift in ecological zonesLoss of habitat and species

Potential Climate Change ImpactsPotential Climate Change Impacts

Climate Changes

Sea Level Rise

Temperature

Precipitation

Source: EPA

• Clear correlation Clear correlation between atmospheric between atmospheric COCO22 and temperature and temperature

over last 160,000 yearsover last 160,000 years

• Current level of COCurrent level of CO22

is is outsideoutside bounds of bounds of natural variabilitynatural variability

•RateRate of change of CO of change of CO22

is also unprecedentedis also unprecedented

Source: OSTP

If nothing is done to slow If nothing is done to slow greenhouse gas emissions. . .greenhouse gas emissions. . .

• COCO22 concentrations will concentrations will

likely be more than 700 ppm likely be more than 700 ppm by 2100by 2100

• Global average temperatures Global average temperatures projected to increase between projected to increase between 2.5 - 10.4°F2.5 - 10.4°F

2100

Source: OSTP

Tree-ring RecordsTree-ring Records

SedimentsSedimentsRecordsRecords

Source: OSTP

+1.4~5.8°C+1.4~5.8°C

+0.10~0.85cm+0.10~0.85cm

Responses to Global WarmingResponses to Global WarmingCoastal lineCoastal line

Glacier RetreatGlacier Retreat

19301930

20012001

Weather ChangeWeather Change

DeforestationDeforestation

Source: OSTP

Palmer Drought Severity Index (The Palmer; PDSI)Palmer Drought Severity Index (The Palmer; PDSI)

4.0 or more extremely wet3.0 to 3.99 very wet2.0 to 2.99 moderately wet1.0 to 1.99 slightly wet0.5 to 0.99 incipient wet spell0.49 to -0.49 near normal-0.5 to -0.99 incipient dry spell-1.0 to -1.99 mild drought-2.0 to -2.99 moderate drought-3.0 to -3.99 severe drought-4.0 or less extreme drought

HealthWeather-related mortalityInfectious diseasesAir-quality respiratory illnesses

AgricultureCrop yieldsIrrigation demands

Water ResourcesChanges in water supplyWater qualityIncreased competition for water

Coastal AreasErosion of beachesInundation of coastal landsCosts to protect coastal communities

ForestsChange in forest compositionShift geographic range of forestsForest health and productivity

Species and Natural AreasShift in ecological zonesLoss of habitat and species

Potential Climate Change ImpactsPotential Climate Change Impacts

Climate Changes

Sea Level Rise

Temperature

Precipitation

Source: EPA

Source: OSTP

• The earth's "greenhouse effect" is what makes this The earth's "greenhouse effect" is what makes this planet suitable for life as we know it.planet suitable for life as we know it.

• The earth's atmosphere contains trace gases, some The earth's atmosphere contains trace gases, some of which absorb heat. These gases (water vapor, of which absorb heat. These gases (water vapor, carbon dioxide, methane, ozone, and nitrous oxide) carbon dioxide, methane, ozone, and nitrous oxide) are referred to as "greenhouse gases." are referred to as "greenhouse gases."

• Albedo has an important influence on the earth's Albedo has an important influence on the earth's temperature.temperature.

• Greenhouses are structures designed to retain heat.Greenhouses are structures designed to retain heat.• The heat-trapping ability of a greenhouse is The heat-trapping ability of a greenhouse is

influenced by a number of factors including the influenced by a number of factors including the transparency of the greenhouse cover, color of the transparency of the greenhouse cover, color of the surfaces inside the greenhouse, and type of surfaces surfaces inside the greenhouse, and type of surfaces inside.inside.

The Greenhouse EffectThe Greenhouse Effect

Venus is too hot, Mars is too cold, and Earth is Venus is too hot, Mars is too cold, and Earth is just right.just right.

Solar radiation interacts with the surface of Solar radiation interacts with the surface of the earth in several ways. Some portion of the earth in several ways. Some portion of this energy is reflected back into space by the this energy is reflected back into space by the earth's atmosphere, another portion is earth's atmosphere, another portion is dispersed and scattered by the molecules in dispersed and scattered by the molecules in the atmosphere and a large portion the atmosphere and a large portion penetrates through the earth's atmosphere to penetrates through the earth's atmosphere to reach the surface of the earth. The radiation reach the surface of the earth. The radiation reaching the earth's surface is largely reaching the earth's surface is largely absorbed resulting in surface warming.absorbed resulting in surface warming.

Much of this absorbed energy is eventually Much of this absorbed energy is eventually re-radiated in longer infrared wavelengths. re-radiated in longer infrared wavelengths. As it leaves the earth, it once again As it leaves the earth, it once again interacts with the atmosphere. Some of this interacts with the atmosphere. Some of this re-radiated energy escapes to space, but re-radiated energy escapes to space, but much of this re-radiated energy is reflected much of this re-radiated energy is reflected back to the earth's surface by molecules in back to the earth's surface by molecules in the earth's atmosphere. This reflected the earth's atmosphere. This reflected energy further warms the surface of the energy further warms the surface of the earth.    earth.    

The molecules responsible for this The molecules responsible for this phenomenon are called greenhouse gases, phenomenon are called greenhouse gases, i.e. water (Hi.e. water (H22O), nitrous oxide (NO), nitrous oxide (N22O), O),

methane (CHmethane (CH44), and carbon dioxide (CO), and carbon dioxide (CO22) )

because they act like the glass in a because they act like the glass in a greenhouse, trapping re-radiated energy. greenhouse, trapping re-radiated energy. Without these gases most life on earth Without these gases most life on earth would not be possible, as the surface would not be possible, as the surface temperature of the earth would likely be temperature of the earth would likely be about 60°F colder.about 60°F colder.

In essence, greenhouse gases act like an In essence, greenhouse gases act like an insulator or blanket above the earth, keeping insulator or blanket above the earth, keeping the heat in. Increasing the concentration of the heat in. Increasing the concentration of these gases in the atmosphere increases the these gases in the atmosphere increases the atmosphere's ability to block the escape of atmosphere's ability to block the escape of infrared radiation. In other words, the infrared radiation. In other words, the earth's insulator gets thicker. Therefore too earth's insulator gets thicker. Therefore too great a concentration of greenhouse gases great a concentration of greenhouse gases can have dramatic effects on climate and can have dramatic effects on climate and significant repercussions upon the world significant repercussions upon the world around us. Climates suitable for human around us. Climates suitable for human existence do not exist simply above some existence do not exist simply above some minimum threshold level of greenhouse gas minimum threshold level of greenhouse gas concentration, rather they exist within a concentration, rather they exist within a finite window - a limited range of greenhouse finite window - a limited range of greenhouse gas concentrations that makes life as we gas concentrations that makes life as we know it possible.know it possible.

Major Greenhouse GasesMajor Greenhouse Gases

•Carbon Dioxide (COCarbon Dioxide (CO22))•Methane (CHMethane (CH44))•Nitrous Oxide (NNitrous Oxide (N22O)O)•Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs)

Carbon Dioxide (CO2)Carbon Dioxide (CO2)

The global Carbon Dioxide budget is complex The global Carbon Dioxide budget is complex and involves transfer of COand involves transfer of CO22 between the between the

atmosphere, the oceans, and the biosphere. atmosphere, the oceans, and the biosphere. Since COSince CO22 is chemically inert, it is not destroyed is chemically inert, it is not destroyed

by photochemical or chemical processes in the by photochemical or chemical processes in the atmosphere; either it is lost by transfer into the atmosphere; either it is lost by transfer into the ocean or biosphere or it builds up in the ocean or biosphere or it builds up in the atmosphere.atmosphere.

Carbon Dioxide Carbon Dioxide Up More Than 30% Since 1750

Each year we add more than 30 billion tons of carbon dioxide to the air mainly by:

• Burning fossil fuels • Cutting down and burning trees

Carbon Dioxide on the Rise

Since 1750, carbon dioxide in the air has risen by more than 30%, due to human activities. It could double by the year 2065.

Methane (CHMethane (CH44))

Methane can be destroyed in the atmosphere via Methane can be destroyed in the atmosphere via reaction with the hydroxyl radical (OH). The reaction with the hydroxyl radical (OH). The major anaerobic environments that produce CHmajor anaerobic environments that produce CH44

include wetlands (150 +/- 50 Tg/yr), rice paddies include wetlands (150 +/- 50 Tg/yr), rice paddies (100 +/- 50 Tg/yr), and enteric fermentation in (100 +/- 50 Tg/yr), and enteric fermentation in the digestive system of cattle, sheep, ect. (100-150 the digestive system of cattle, sheep, ect. (100-150 Tg/yr). Tg/yr).

CH4: Methane

Methane More Than Doubled Since 1750

Each year we add 350 to 500 million tons of methane to the air mainly by:

• Raising livestock • Coal mining and drilling for oil and natural gas • Rice cultivation • Disposing of garbage in landfills • Burning forests and fields

Methane on the Rise Since 1750, methane in the air has more than doubled due to human activity. It could double again by 2050.

Nitrous Oxide (NNitrous Oxide (N22O)O)

Nitrous oxide is chemically inert in the Nitrous oxide is chemically inert in the troposphere. However, Ntroposphere. However, N22O is destroyed in the O is destroyed in the

stratosphere via photolysis by solar radiation, stratosphere via photolysis by solar radiation, which is responsible for about 90% of its which is responsible for about 90% of its destruction, and by reaction with excited atomic destruction, and by reaction with excited atomic oxygen, O(1D), which is responsible for about oxygen, O(1D), which is responsible for about 10% of its destruction.10% of its destruction.

N2O: Nitrous Oxide

Nitrous Oxide Up More Than 15% Since 1750

Three main kinds of fluorocarbons make the largest contributions to the greenhouse effect:

Chemical Fertilizers: The Main Source Nitrogen-based fertilizer use has doubled in the past 15 years.

Sewage Emits Nitrous OxideHuman and animal wastes release nitrous oxide. Sewage treatment plants may be a major source of this gas.

Nitrous Oxide on the Rise

Since 1750, nitrous oxide in the atmosphere has risen by more than 15 percent.

•Chlorofluorocarbons (CFC-11 and CFC-12)Chlorofluorocarbons (CFC-11 and CFC-12)

CFC-11 and CFC-12 are chemically inert in the CFC-11 and CFC-12 are chemically inert in the troposphere and diffuse up to the stratosphere, troposphere and diffuse up to the stratosphere, where they are destroyed by photolysis by solar where they are destroyed by photolysis by solar radiation and by reaction with excited atomic radiation and by reaction with excited atomic oxygen.oxygen.

Fluorocarbons Fluorocarbons Come Almost Entirely

From Human Activities

Three main kinds of fluorocarbons make the largest contributions to the greenhouse effect:

• CFCs (chlorofluorocarbons) destroy ozone. Their use is being phased out. • HCFCs (hydrochlorofluorocarbons) destroy ozone, although less than CFCs. They are also being phased out. • HFCs (hydrofluorocarbons) do not destroy ozone, but still trap heat in the atmosphere.

Climate Feedbacks on an Enhanced Climate Feedbacks on an Enhanced Greenhouse EffectGreenhouse Effect

•OceanOcean•VegetationVegetation•Clouds & Water VaporClouds & Water Vapor•Sea IceSea Ice

OceanOcean

The world's oceans have complicated reactions or The world's oceans have complicated reactions or feedbacks on the enhanced greenhouse effect. On feedbacks on the enhanced greenhouse effect. On one hand, they can provide sources for the one hand, they can provide sources for the increased water vapor as the earth becomes increased water vapor as the earth becomes warming. On the other hand, the thermal holding warming. On the other hand, the thermal holding capacity of the oceans would delay and effectively capacity of the oceans would delay and effectively reduce the observed global warming.reduce the observed global warming.

VegetationVegetationVegetation changes caused by a climate change Vegetation changes caused by a climate change would affect the hydrologic cycle and surface would affect the hydrologic cycle and surface albedo. Furthermore, high temperature appears to albedo. Furthermore, high temperature appears to be detrimental to seed growth because it shortens be detrimental to seed growth because it shortens the time period for this stage of growth in many the time period for this stage of growth in many plants. However, the rise of atmospheric COplants. However, the rise of atmospheric CO22

concentration should cause increase in concentration should cause increase in photosynthesis, growth and productivity of the photosynthesis, growth and productivity of the earth's vegetation. Thus, the direct effects of rising earth's vegetation. Thus, the direct effects of rising COCO22 and expected climate change should have a and expected climate change should have a

less adverse impact on vegetation than climate less adverse impact on vegetation than climate change alone.change alone.

Clouds & Water VaporClouds & Water Vapor

Global warming will lead to an increase in the Global warming will lead to an increase in the amount of water vapor in the atmosphere and amount of water vapor in the atmosphere and because water vapor is a powerful greenhouse gas, because water vapor is a powerful greenhouse gas, this will lead to an increase in the warming. this will lead to an increase in the warming. However, some scientists propose that tropical However, some scientists propose that tropical storm clouds would reach higher in the storm clouds would reach higher in the atmosphere under warmer conditions. Then the atmosphere under warmer conditions. Then the clouds would produce more rain thus adding less clouds would produce more rain thus adding less water vapor to the middle troposphere. The water vapor to the middle troposphere. The resulting drier middle troposphere will produce a resulting drier middle troposphere will produce a negative feedback to the global warming.negative feedback to the global warming.

Sea IceSea Ice

Generally, increased temperature would tend to Generally, increased temperature would tend to melt ice and result in increased absorption of solar melt ice and result in increased absorption of solar energy by the ocean, a positive feedback. However, energy by the ocean, a positive feedback. However, a decrease in sea ice would also lead to larger heat a decrease in sea ice would also lead to larger heat fluxes from the ocean to the atmosphere, a negative fluxes from the ocean to the atmosphere, a negative feedback. Thus, the interaction among the feedback. Thus, the interaction among the atmosphere, the ocean, sea ice, and the sensitivity of atmosphere, the ocean, sea ice, and the sensitivity of sea ice to climate change need to be observed and sea ice to climate change need to be observed and quantified.quantified.

Burning of fossil fuelsBurning of fossil fuels

Source: OSTP

Source: OSTP

Projected Changes in Annual Temperatures for the 2050sProjected Changes in Annual Temperatures for the 2050s

The projected change is compared to the present day with a ~1% increase per year in equivalent COThe projected change is compared to the present day with a ~1% increase per year in equivalent CO 22

Source: The Met Office. Hadley Center for Climate Prediction and Research

Sea-Level RiseSea-Level Rise

Warning Signs Today for Sea-Level RiseWarning Signs Today for Sea-Level Rise

• The current pace of sea-level rise is three The current pace of sea-level rise is three times the historical rate and appears to be times the historical rate and appears to be accelerating.accelerating.

• Global sea level has already risen by four to Global sea level has already risen by four to eight inches in the past century. Scientists' eight inches in the past century. Scientists' best estimate is that sea level will rise by an best estimate is that sea level will rise by an additional 19 inches by 2100, and perhaps by additional 19 inches by 2100, and perhaps by as much as 37 inches.as much as 37 inches.

Ice Core RecordsIce Core Records

Ozone Hole and Greenhouse Effects Ozone Hole and Greenhouse Effects

The Ozone Hole often gets confused in the popular The Ozone Hole often gets confused in the popular press and by the general public with the problem press and by the general public with the problem of global warming. Whilst there is a connection of global warming. Whilst there is a connection because ozone contributes to the greenhouse effect, because ozone contributes to the greenhouse effect, the Ozone Hole is a separate issue. However it is the Ozone Hole is a separate issue. However it is another stark reminder of the effect of man's another stark reminder of the effect of man's activities on the environment.activities on the environment.

Over Antarctica (and recently over the Arctic), Over Antarctica (and recently over the Arctic), stratospheric ozone has been depleted over the last stratospheric ozone has been depleted over the last 15 years at certain times of the year. This is mainly 15 years at certain times of the year. This is mainly due to the release of manmade chemicals containing due to the release of manmade chemicals containing chlorine such as CFC's (ChloroFluoroCarbons), but chlorine such as CFC's (ChloroFluoroCarbons), but also compounds containing bromine, other related also compounds containing bromine, other related halogen compounds and also nitrogen oxides (NOhalogen compounds and also nitrogen oxides (NO

xx). ).

CFC's are a common industrial product, used in CFC's are a common industrial product, used in refrigeration systems, air conditioners, aerosols, refrigeration systems, air conditioners, aerosols, solvents and in the production of some types of solvents and in the production of some types of packaging. Nitrogen oxides are a by-product of packaging. Nitrogen oxides are a by-product of combustion processes, eg. aircraft emissions.combustion processes, eg. aircraft emissions.

What Is The Ozone Hole? What Is The Ozone Hole?