Homework on Climate Change: An investigation into effects of climate change on the planet and our role in those changes.
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ClimateChange.pptxClimate Change
Past, Present and Future
Day After Tomorrow_Bouys
Climate and Weather
Climate refers to characteristic atmospheric conditions over a long period of time
years or decades
Weather refers to atmospheric conditions over short periods of time
Days or weeks
Packing for a vacation you check the weather to know how to pack.
Climate Zones
Temperature and precipitation simplest way to classify zones
Climate can be affected by processes and changes that maintain the climate system
Ocean currents
Topography
Atmospheric gases
Climate Zones
Climate Zones
Climate and Natural Processes
Climate major influence on natural processes
Flooding dependent on rainfall amount and intensity
Wildfires more likely in dry areas
Understanding climate can indicate things about likely hazards
The Atmosphere
Atmosphere gases are split into 2 categories
Permanent gases
Variable gases
The Atmosphere
Atmosphere gases are split into 2 categories
Permanent gases
Gases whose proportions stay constant
Have little effect atmospherically
Ex. O, N and Ar
Variable gases
The Atmosphere
Atmosphere gases are split into 2 categories
Permanent gasses
Variable gases
Gases whose proportions vary with time
Play important roles in atmospheric dynamics
Water vapor, carbon dioxide (CO2), methane (CH4), etc.
The Atmosphere
The Atmosphere
The major permanent gases in the atmosphere include N, O and Ar. Together they comprise about 99% of atmospheric gasses.
While variable gases comprise a small percentage of the atmosphere they play an important role in atmospheric dynamics.
Variable gases are considered “Greenhouse Gases”
The Atmosphere
There are several greenhouse gases, why do we only hear about CO2 in the news?
Methane (CH4)
Second most important Greenhouse gas.
More potent than CO2
Exist in far lower concentrations
Considerably shorter residence time (~10 years)
Carbon dioxide (CO2)
Third most potent greenhouse gas
Fluctuates seasonally
Concentration approx. 400ppm
Much longer residence time (50-200+years)
The Atmosphere
The Atmosphere
Study of Past Climate Change
Over the past 3.2 million years, Earth’s climate system has fluctuated greatly and alternated between periods of glaciation
Data available from three main sources
Instrumental Record
Historical Record
Paleo-Proxy Record
Study of Past Climate Change
Data available from three main sources
Instrumental Record
Measurements of temperature made directly since 1860
CO2 measurements from 1960
Solar energy from past several decades
Historical Record
Paleo-Proxy Record
Study of Past Climate Change
Study of Past Climate Change
Data available from three main sources
Instrumental Record
Historical Record
Written recollections (Books, newspapers, journal articles, personal journals, etc.)
Paleo-Proxy Record
Study of Past Climate Change
Data available from three main sources
Instrumental Record
Historical Record
Paleo-Proxy Record
Data can be correlated with climate
Data are not a direct measurement of temperature
Provide the best evidence that predates the historical and instrumental records
Study of Past Climate Change
Paleoclimate proxy data sources
Tree rings: Growth of trees depends on rainfall and temperature variability
Extends back more than 10,000 years
Sediment: Drilling into ocean or lakes
Chemicals are interpreted to provide data on climate change
Ice cores: Obtained by drilling into glacial ice
Contains small bubbles of air trapped during snow fall
Composition and ratio of past atmospheric gases are studied
Ice is studied to determine the composition of the water
Day After Tomorrow_Ice Shelf
Study of Past Climate Change
Paleoclimate proxy data sources
Pollen: collects in environment
Type and abundance of pollen found reflect climate
Corals: CaCO3 contains isotopes of oxygen that can be analyzed for temperature
14C: Can give information about sunspot activity
Can be found in tree ring data
Can help explain some of the warming during the Medieval Warming period and cooling during the Little Ice Age.
CO2: Most important proxy for temperature change
Data comes from instrumental record and ice core samples
Study of Past Climate Change
Air temperature changes correspond closely to atmospheric CO2
Study of Past Climate Change
Study of Past Climate Change
Global Warming
Observed increase in average temperature of land and ocean during the past 60 years
Both human and natural processes are contributing to warming
But who/what is more to blame?
The Greenhouse Effect
Earth’s temperature depends on:
Amount of sunlight received
Amount of sunlight reflected
Amount of reradiated heat that is retained
The Greenhouse Effect
Sun’s radiation is absorbed by Earth and atmosphere
Greenhouse gases: Water vapor, CO2, CH4 and CFC’s
Greenhouse gases absorb infrared radiation reflected by Earth’s surface and are warmed
The Greenhouse Effect
The Greenhouse Effect
Greenhouse effect is a natural and necessary process
Earth would be 33º colder without it
All surface water would be frozen
Little life would exist
Most of the natural effect is from water vapor
Human activities have increased amounts of greenhouse gases
Anthropogenic (human caused) component of warming
The Greenhouse Effect
CO2 accounts for most of the anthropogenic greenhouse effect
CO2 concentration
Past concentrations have varied between 200 ppm to about 300 ppm
Today concentration is approximately 400 ppm
Predicted to reach at least 450 ppm by the year 2050
Global Temperature Change
Last 800,000 years
Low temperatures coincide with major continental glaciations. High temperatures with interglacial periods
Last 150,000 years
Last major interglacial period. Sea level was 4-6 feet higher than today
Last 18,000 years
Cold interval, Younger Dryas, occurred 11,500 years ago, followed by warming
Recent cooling, called Little Ice Age, 15th-19th centuries
Global Temperature Change
Global Temperature Change
Last 1,000 years
Several warming and cooling trends
Warming in A.D. 1100-1300 allowed Vikings into Iceland, Greenland and North America
Last 140 years
1750, warming trend begins until 1940s
1910 to 1998, global temperatures rise
Most of the increase since the 1970s
1990s and first decade of twenty-first century warmest temperatures since monitoring began
Global Temperature Change
Global Temperature Change
Why does Climate Change?
Natural causes of climate change
Long-term
Short-term
Milankovitch Cycles
Why does Climate Change?
Natural causes of climate change
Long-term
Milankovitch cycles: natural changes in Earth’s orbit, tilt and precession
Explain some changes, but not the observed large scale changes
Short-term
Milankovitch Cycles
100,000 years
~40,000 years
~20,000 years
Why does Climate Change?
Milankovitch Cycles: Natural changes in Earth’s orbit, tilt and precession
What causes fluctuations?
Gravitational pull of other planets
Irregular shape of Earth and gravitational pull of moon
Why does Climate Change?
Natural causes of climate change
Long-term
Short-term
Climate forcing: An imposed change of Earth’s energy balance
Types of forcing
Volcanic
Ocean Conveyor Belt
Anthropogenic
Volcanic Forcing
Ash from eruptions becomes suspended in the atmosphere, reflects sunlight having a cooling effect
Aerosol cooling may help explain disparity between recorded temperatures that are lower than normal
Mt. Pinatubo (1991) counterbalanced global warming during 1991 and 1992
Volcanic forcing is believed to have contributed to the cooling of the Little Ice Age
Ocean Conveyor Belt
Circulation of ocean water in oceans
Can cause fast changes in climate
In Atlantic Ocean
Strong northward movement of near-surface waters are cooled when they arrive near Greenland
The water cools, becomes saltier and denser, and it sinks to the bottom
Current then flows southward around Africa
Huge amounts of warm water keep Europe warmer than it would be otherwise
Full cycle takes ~1000 years
Ocean Conveyor Belt
Why does Climate Change?
Scientific uncertainties exist, but there is sufficient evidence to state:
There is discernible human influence on global climate
Warming is now occurring
Mean surface temperature of Earth will likely increase between 1.5º and 4.5º (2.6-7.8ºF) this century
Why does Climate Change?
Human-induced component (anthropogenic)
Increases emissions of gases that trap heat
There has been strong correlation between the concentration of atmospheric CO2 and global temperatures
Why does Climate Change?
Anthropogenic Forcing
Refers to human-related forcing
Most important are emissions of greenhouse gases
Evidence of anthropogenic forcing is based on:
Recent warming of 0.2ºC (0.4ºF) per decade cannot be explained by natural variability of the climate over recent geologic history
Industrial age forcing of is mostly due to emissions of CO2
Climate models suggest that the rise in global land temperatures is not only from natural forcing. Combining both natural and anthropogenic forcing helps to explain the observed changes
So the Earth is Warming. So What?
So the Earth is Warming. So What?
Glaciers and Sea Ice
Concern global warming is accelerating melting of ice sheets and mountain glaciers
Affects communities dependent on snowmelt for water supply
Glaciers are retreating worldwide
Response to mean global temperature above the long-term mean temperature from 1977-1994
Most glaciers in Glacier National Park may be gone by 2030
Glaciers in European Alps will be gone by the end of the century
Glaciers and Sea Ice
Glaciers and Sea Ice
Glaciers and Sea Ice
Glaciers and Sea Ice
Positive feedback cycle
Snow and ice reflect radiation, keeping temperatures low
Melting exposes darker ground, absorbs radiation increasing temperature
More ice that melts, faster the warming and increased melting occurs
Arctic sea ice
Declines 10% each decade (May be ice free on or before 2030 if trends continue)
Additional impact is that newer ice is thinner and thus stores less water
Glaciers and Sea Ice
Sea-Level Rise
Near surface ocean temperature have increased
Warming causes ocean water to expand, raising sea level
Some conclusions:
Thermal expansion and melting glacial ice contribute to the observed sea-level rise since 1961
Difference between observed and estimated sea level rise is considerable, suggesting that additional research is needed
Rates of thermal expansion and melting glacial ice are accelerating
The Greenland ice sheet’s contribution to sea-level rise has increased about 4 times in recent decades
Sea-Level Rise
Sea-Level Rise
Reducing the Impact (Kyoto)
1997 United Nations Framework Convention on Climate Change in Kyoto, Japan
An international agreement to reduce emissions of CO2
Signed by 166 nations
United States and Australia did NOT sign agreement
European Union has become a leader on climate change issues
Day After Tomorrow_Conference
Reducing the Impact (Kyoto)
Reasons why US did NOT ratify protocol
Developed countries required to reduce CO2 below 1995 levels
Amount of reduction depended on country
Proposed reduction in US only 6%
Developing countries excluded
Reducing the Impact
Reducing the Impact (Kyoto)
Suggestions on what needs to change in order for US to join
Include developing countries
Give credit for reforestation
Enforcement of protocol
Reducing the Impact
Ways to reduce emissions
Improved engineering of fossil fuel-burning power plants
Use those fossil fuels that release less carbon into the atmosphere, such as natural gas
Conserve energy to reduce dependence on fossil fuels
Collect and store carbon in Earth’s systems, such as forests, soils and rocks below the surface of Earth
Reducing the Impact
Possible Government Policies
CO2 tax
Emissions trading (Cap and Trade)
More stringent standard fuel economy
Planting more trees
Funding for alternative energy
Get the government to accept that climate change is, in fact, real and scientifically provable and willing to pass legislation that limits emissions on CO2 producers!
Possible Government Policies
Abrupt Climate Change
Risk to humans and natural environment
Rapid sea level change from changes in glaciers and ice sheets
Droughts and floods from widespread rapid changes to the hydrologic cycle
Abrupt changes in Ocean Conveyor Belt, characterized by northward flow of warm, salty water in upper regions
Rapid release of methane to atmosphere from melting permafrost and ocean’s sediment
Abrupt Climate Change
Appears abrupt climate change is unlikely in next century
Sea level rise and droughts are the most likely to occur abruptly
However, uncertain about predictions
Changes in the Atlantic Ocean circulation and methane is unlikely to occur in the next 100 years
Ultimately, we need more geologic data to understand the past to make predictions on the future
