1. Global Environmental Change
Climate Change, Global Warming, Ozone Depletion…
…what’s going on?

2. Stratospheric Ozone Depletion

3. What are Halogen Gases?

4. Where do CFC’s come from?

5. Where else can we find Ozone depleting chemicals?

6. How long do CFC’s last???
The chlorine atoms can break down tens of thousands of ozone molecules before being removed from the stratosphere. Given the longevity of CFC molecules, recovery times are measured in decades. It is calculated that a CFC molecule takes an average of 15 years to go from the ground level up to the upper atmosphere, and it can stay there for about a century, destroying up to one hundred thousand ozone molecules during that time.

7. What are the effects of Ozone depletion?
Skin cancer
Cataracts
Damage to crops
Loss in productivity of phytoplankton in the ocean.,

8. Montreal Protocol
After a series of rigorous meetings and negotiations, the Montreal Protocol on Substances that Deplete the Ozone Layer was finally agreed upon on 16 September 1987 at the Headquarters of the International Civil Aviation Organization in Montreal. The Montreal Protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere--chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform--are to be phased out by 2000 (2005 for methyl chloroform). Scientific theory and evidence suggest that, once emitted to the atmosphere, these compounds could significantly deplete the stratospheric ozone layer that shields the planet from damaging UV-B radiation.

9. Back to the Troposphere
Climate change is the fastest-developing area of environmental science

10. What is Climate?
Climate = the average and variations of weather over a long period of time (~30 years)
The changes in temperature, moisture, wind, precipitation, etc.
Climate is defined as the weather averaged over a long period of time.
The standard averaging period is 30 years but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations.
Therefore, climate is “the average and variations of weather over long periods of time”.
Different “Climate Zones” such as tropical, temperate or polar can be defined using parameters such as temperature and rainfall.
Above: Global average for atmospheric water vapor.

11. What is Weather?
Weather = all natural phenonmena within the atmosphere at a given time (hours to days)
Short-term conditions at localized sites
“Weather” is the set of all phenomena in a given atmosphere at a given time.
The term usually refers to the activity of these phenomena over short periods (hours or days), as opposed to the term climate, which refers to the average atmospheric conditions over longer periods of time. When used without qualification, "weather" is understood to be the weather of Earth.
On Earth, common weather phenomena include such things as wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as cyclones and ice storms.
Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere - see figure on left). Weather does occur in the stratosphere and can affect weather lower down in the troposphere, but the exact mechanisms are poorly understood.

12. What is climate change?
Global climate change = describes trends and variations in Earth’s climate
Temperature, precipitation, storm frequency
Global warming and climate change are not the same
Global warming = an increase in Earth’s average temperature
Only one aspect of climate change

13. Global warming
Climate change and global warming refer to current trends
Earth’s climate has varied naturally through time
The current rapid climatic changes are due to humans
Fossil fuel combustion and deforestation
Understanding climate change requires understanding how our planet’s climate works

14. The sun and atmosphere keep Earth warm
Four factors exert the most influence on climate
The sun = without it, Earth would be dark and frozen
Supplies most of Earth’s energy
The atmosphere = without it, Earth’s temperature would be much colder
The oceans = shape climate by storing and transporting heat and moisture
How Earth spins, tilts, and moves through space influence how climate varies over long periods of time

15. The Climate System Land Ice Oceans Atmosphere Biosphere
The Earth has many different systems that interact with each other in different ways.
Ice
Biosphere
The climate includes interaction between all areas on the surface of the Earth and in the atmosphere.
For example, water is evaporated from the ocean to form water vapor clouds in the atmosphere. The wind can then carry these clouds over the land where the water falls as rain or snow. Eventually the water may return to the ocean via rivers etc.
Also, the biosphere the living plants and animals, live in and utilize the land, sea and sky - so you can see how everything is connected.
Land

16. The fate of solar radiation
The atmosphere, land, ice, and water absorb 70% of incoming solar radiation

17. Greenhouse gases warm the lower atmosphere
As Earth’s surface absorbs solar radiation, the surface increases in temperature and emits infrared radiation
Greenhouse gases = atmospheric gases that absorb infrared radiation
Water vapor, ozone, carbon dioxide, nitrous oxide, methane, halocarbons [chlorofluorocarbons (CFCs)]
After absorbing radiation, greenhouse gases re-emit infrared energy, losing some energy to space
Greenhouse effect = energy that travels downward, warming the atmosphere and the planet’s surface

18. Modern Climate Systems
Atmosphere and Greenhouse Effect
The Earth’s atmosphere keeps it around 30°C warmer than it would otherwise be.
This is the Greenhouse Effect
The atmospheric composition on Earth is largely governed by the by-products of the life that it sustains.
Earth's atmosphere consists principally of a roughly 78:20 ratio of nitrogen and oxygen, plus substantial water vapor (gas), with a minor proportion of carbon dioxide. There are traces of hydrogen, and of argon, helium and other "noble" gases (and of volatile pollutants).
The role of the Earth’s atmosphere is varied.
It’s the environment for most of its biological activity
The atmosphere (as we have seen) exerts considerable influence on the weather and climate and also ocean circulation.
The atmosphere protects earth's life forms from harmful radiation and cosmic debris.
The ozone layer within the atmosphere also protects the earth from the sun's harmful ultraviolet rays.
The atmosphere, more specifically the thermosphere and mesosphere cause meteors that hit it to burn up from the heat generated by air friction.
Importantly, if the Earth did not have an atmosphere the average global temperature would be 30 degrees Celsius below what it is today! (Presenter: this leads into the next slide on the Greenhouse Effect….)
The temperature of the Earth depends on the amount of energy we receive from the sun versus the amount of energy lost back out to space.

19. The greenhouse effect is natural
Greenhouse gases have always been in the atmosphere
We are not worried about the natural greenhouse effect
Anthropogenic intensification is of concern
Global warming potential = the relative ability of one molecule of a greenhouse gas to contribute to warming
Expressed in relation to carbon dioxide (potential = 1)
Methane is 25 times as potent as carbon dioxide

20. Carbon dioxide is of primary concern
It is not the most potent greenhouse gas, but it is extremely abundant
The major contributor to the greenhouse effects
CO2 exerts six times more impact than methane, nitrous oxide, and halocarbons combined
Deposition, partial decay, and compression of organic matter (mostly plants) in wetlands or marine areas led to formation of coal, oil, and natural gas
These deposits remained buried for millions of years

21. The Carbon Cycle

22. What caused levels of CO2 to increase?
Burning fossil fuels transfer CO2 from lithospheric reservoirs into the atmosphere
The main reason atmospheric carbon dioxide concentrations have increased so dramatically
Deforestation contributes to rising atmospheric CO2
Forests serve as reservoirs for carbon
Removing trees reduces the carbon dioxide absorbed from the atmosphere
Human activities increased atmospheric CO2 from 280 parts per million (ppm) to 389 ppm
The highest levels in more than 800,000 years

23. Other greenhouse gases add to warming
Methane = fossil fuels, livestock, landfills, crops (rice)
Levels have doubled since 1750
Nitrous oxide = feedlots, chemical manufacturing plants, auto emissions, and synthetic nitrogen fertilizers
Ozone levels have risen 36% due to photochemical smog
Halocarbon gases (CFCs) are declining due to the Montreal Protocol
Water vapor = the most abundant greenhouse gas
Contributes most to the natural greenhouse effect
Concentrations have not changed

24. U.S. emissions of major greenhouse gases

25. Feedback complicates our predictions
Tropospheric warming will transfer more water to the air
But the effects are uncertain
A positive feedback loop = more water vapor … more warming … more evaporation … more water vapor …
A negative feedback loop = more water vapor … more clouds … shade and cool Earth OR increase evaporation
Minor modifications of the atmosphere can lead to major effects on climate

26. Most aerosols exert a cooling effect
Aerosols = microscopic droplets and particles
They have either a warming or a cooling effect
Soot (black carbon aerosols) causes warming by absorbing solar energy
But most tropospheric aerosols cool the atmosphere by reflecting the sun’s rays
Sulfate aerosols produced by fossil fuel combustion may slow global warming, at least in the short term
Volcanic eruptions reduce sunlight reaching Earth’s surface and cool the Earth

27. Radiative forcing expresses change in energy
Radiative forcing = the amount of change in thermal energy that a given factor causes
Positive forcing warms the surface
Negative forcing cools it
Earth is experiencing radiative forcing of 1.6 watts/m2 more than it is emitting to space – enough to alter the climate

28. Milankovitch cycles influence climate
Milankovitch cycles = periodic changes in Earth’s rotation and orbit around the sun
Alter the way solar radiation is distributed over Earth
These cycles modify patterns of atmospheric heating
Triggering climate variation
For example, periods of cold glaciation and warm interglacial times

29. Solar output and ocean absorption influence climate
Solar output = the sun varies in the radiation it emits
Variation in solar energy (e.g., solar flares) has not been great enough to change Earth’s temperature
Radiative forcing is 0.12 watts/m2 – much less than human causes
Ocean absorption = the ocean holds 50 times more carbon than the atmosphere
Slowing global warming but not preventing it
Warmer oceans absorb less CO2
A positive feedback effect that accelerates warming

30. Ocean circulation influences climate
Ocean circulation = ocean water exchanges heat with the atmosphere,
Currents move energy from place to place
The ocean’s thermohaline circulation system affects regional climates
Moving warm tropical water north, etc.
Greenland’s melting ice sheet will affect this flow
El Niño–Southern Oscillation (ENSO)
Shifts atmospheric pressure, sea surface temperature, ocean circulation in the tropical Pacific

31. Direct measurements tell us about the present
We document daily fluctuations in weather
Precise thermometer measurements over the past 100 years
Measuring of ocean and atmospheric chemistry began in 1958
Precise records of historical events
Droughts, etc.
Atmospheric CO2 concentrations have increased from 315 ppm to 389 ppm

32. How Do We Know about Past Climate Systems
1. Early human record
A record of past local environmental conditions may be preserved in early rock art and sculpture.
For example, rock paintings from Tassili N´Ajjer in Algeria show that the region in Neolithic times was moist and fertile, with abundant water and wildlife. The art depicts herds of cattle, large wild animals including crocodiles, and human activities such as hunting and dancing.
This area now hosts a sandstone mountain range located in a desert.
More than 15,000 drawings and engravings record the climatic changes, the animal migrations and the evolution of human life on the edge of the Sahara from 6000 B.C. to the first centuries of the present era.
cc. W.V. Bailey
Rock paintings provide evidence of fertile Sahara region (now desert) 6,000 years ago.
Tourism NT

33. Past Climate Systems 2. Geomorphology
Geomorphology is the study of landforms, including their origin and evolution, and the processes that shape them.
Studying of surface features such as valleys, mountains, river beds, ancient dune and lake deposits can tell you what the environment was like in the past.
For example, the Lake District in North West England has many valleys shaped like a “U”. They have flat bottoms and steep sides. (As opposed to River Valleys that are typically “V” shaped).
These were formed by the passage of glaciers that carved their way through the landscape. There are no glaciers there today but from the physical features they left behind we can tell that the area was once covered in ice.
River deltas show where rivers entered the ocean or a lake.
Above: A “U” shaped valley shows that it was formed by a glacier.

34. Past Climate Systems 4. Ice cores
Ice cores can preserve seasonal layering. Studying the chemistry of each layer can give clues about climate change.
An ice core is a core sample from the accumulation of snow and ice over many years that have recrystallised and have trapped air bubbles from previous time periods. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides scientists with a picture of the climate at the time.
Water molecules containing heavier isotopes exhibit a lower vapor pressure, when the temperature falls, the heavier water molecules will condense faster than the normal water molecules. The relative concentrations of the heavier isotopes in the condensate indicate the temperature of condensation at the time, allowing for ice cores to be used in global temperature reconstruction, I.e. by measuring the isotope ratios of the frozen water in the ice cores scientists can reconstruct what the temperature was when the water was frozen
In addition to the isotope concentration, the air bubbles trapped in the ice cores allow for measurement of the atmospheric concentrations of trace gases, including greenhouse gases carbon dioxide, methane, and nitrous oxide.
The bottom photograph shows a section of the GISP2 ice core from meters in which annual layers are clearly visible. The appearance of the dark and light layers results from differences in the size of snow crystals deposited in winter versus summer and resulting variations in the abundance and size of air bubbles trapped in the ice. Counting such layers has been used (in combination with other techniques) to reliably determine the age of the ice. In this case the ice was formed ~16250 years ago during the final stages of the last ice age and approximately 38 years are represented in the photo.
Therefore, by analyzing the ice and the gases trapped within, scientists are able to learn about past climate conditions.
GISP2 ice core at 1837m depth with clearly visible annual layers.

35. Ice cores from Antarctica
Ice cores let us go back in time 800,000 years
Reading Earth’s history across eight glacial cycles

36. Is the Climate Changing?
In the following section we will discuss the past and current trends in climate change and use these models to look towards the future.

37. What are the current climate trends?
Global temperature for the last 150 years
Geologically recent trends in climate show an increase in global temperatures.
This figure shows the change in temperature over the past 150 years based on measurements compiled by the Climatic Research Unit of the University of East Anglia and the Hadley Centre of the UK Meteorological Office.
The “zero” point on this figure is the mean temperature from
The results show a general temperature increase of /- 0.17°C.
cc. Robert A. Rohde

38. Temperatures continue to increase
Average surface temperatures increased 0.74 °C since 1906
Most of the increase occurred in the last few decades
Extremely hot days have increased
The 16 warmest years on record have been since 1990

39. The future will be hotter
In the next 20 years, temperatures will rise 0.4 °C
At the end of the 21st century, temperatures will be 1.8–4.0 °C higher than today’s
We will have unusually hot days and heat waves
Polar areas will have the most intense warming
Sea surface temperatures will rise
Hurricanes and tropical storms will increase
In power and duration

40. Temperatures will rise globally
Projected increases in surface temperature for 2090–2099 relative to 1980–1999

41. Precipitation is changing, too
Some regions are receiving more precipitation than usual, and others are receiving less
Droughts have become more frequent and severe
Harming agriculture, promoting soil erosion, reducing water supplies, and triggering fires
Heavy rains contribute to flooding
Killing people, destroying homes, and inflicting billions of dollars in damage

42. Projected changes in precipitation
Precipitation will increase at high latitudes and decrease at low and middle latitudes

43. Melting snow and ice Mountaintop glaciers are disappearing
Glaciers on tropical mountaintops have disappeared
The remaining 26 of 150 glaciers in Glacier National Park will be gone by 2020 or 2030
Reducing summertime water supplies
Melting of Greenland’s Arctic ice sheet is accelerating
Warmer water is melting Antarctic coastal ice shelves
Interior snow is increasing due to more precipitation
Melting ice exposes darker, less-reflective surfaces, which absorb more sunlight, causing more melting

44. Coral reefs are threatened
Coral reefs are habitat for food fish
Snorkeling and scuba diving sites for tourism
Warmer waters contribute to coral bleaching
Which kills corals
Increased CO2 is acidifying the ocean
Organisms can’t build their exoskeletons
Oceans have already decreased by 0.1 pH unit
Enough to kill most coral reefs

45. Climate change affects organisms and ecosystems
Organisms are adapted to their environments
They are affected when those environments change
Global warming modifies temperature-dependent phenomena (e.g., timing of migration, breeding)
Animals and plants will move toward the poles or upward in elevation
20–30% of species will be threatened with extinction
Rare species will be pushed out of preserves
Droughts, fire, and disease will decrease plant growth
Fewer plants means more CO2 in the atmosphere

46. Climate change affects people
Societies are feeling the impacts of climate change
Agriculture: shortened growing seasons, decreased production, crops more susceptible to droughts
Increasing hunger
Forestry: increased fires, invasive species
Insect and disease outbreaks
Health: heat waves and stress can cause death
Respiratory ailments, expansion of tropical diseases
Disease and sanitation problems from flooding
Drowning from storms

47. Impacts of climate change
The Arctic has suffered the most so far
U.S. temperatures will continue to rise

48. Impacts of climate change will vary

49. Predictions from two climate models
By 2050, Illinois will have a climate like Missouri’s
By 2090, it will have a climate like Louisiana’s

50. Causes and consequences of climate change

51. Shall we pursue mitigation or adaptation?
Most people accept that our planet is changing
They are searching for solutions
Mitigation = pursue actions that reduce greenhouse gas emissions to lessen severity of future climate change
Energy efficiency, renewable energy, protecting soil, preventing deforestation
Adaptation = accept that climate change is happening
Pursue strategies to minimize its impacts on us
Seawalls, leaving the area, coping with drought, etc.
Both are necessary

52. Electricity generation
A coal-fired, electricity-generating power plant
The largest source of U.S. CO2 emissions
70% of electricity comes from fossil fuels
Coal causes 50% of emissions
To reduce fossil fuel use:
Encourage conservation and efficiency
Switch to cleaner and renewable energy sources

53. Conservation and efficiency
We can make lifestyle choices to reduce electricity use
Use fewer greenhouse-gas-producing appliances
Use electricity more efficiently
The EPA’s Energy Star Program rates appliances, lights, windows, etc. by their energy efficiency
Replace old appliances with efficient ones
Use compact fluorescent lights
Use efficient windows, ducts, insulation, heating and cooling systems

54. Sources of electricity
We need to switch to clean energy sources
Nuclear power, biomass energy, solar, wind, etc.
We need to consider how we use fossil fuels
Switching from coal to natural gas cuts emissions 50%
Cogeneration produces fewer emissions
Carbon capture = removes CO2 from power plant emissions
Carbon sequestration (storage) = storing carbon underground where it will not seep out
Use depleted oil and gas deposits, salt mines, etc.
We can’t store enough CO2 to make a difference

55. Transportation
2nd largest source of U.S. greenhouse gases
Cars are inefficient
Ways to help:
More efficient cars
Hybrid or electric cars
Drive less and use public transportation
Live near your job, so you can bike or walk
U.S. public transportation saves 4.2 billion gallons of gasoline and 37 million metric tons of CO2 emissions

56. We can reduce emissions in other ways
Agriculture: sustainable land management lets soil store more carbon
Reduce methane emissions from rice and cattle
Grow renewable biofuels
Forestry: reforest cleared land, preserve existing forests
Sustainable forestry practices
Waste management: treating wastewater
Generating electricity by incinerating waste
Recovering methane from landfills
Individuals can recycle, compost, reduce, or reuse goods

57. Questions to be answered…
How fast will the sea level rise?
How much warmer will it get?
When will the Arctic Ocean be ice-free?
Will the water cycle accelerate?
Are climate extremes increasing?
Will there be abrupt changes?
Presenter: read through questions as they appear one by one…these are the hot topics of debate at the moment.
We know from studying the past climate cycles that humans are having an influence on the current conditions. Scientists have identified these questions as important but we don’t yet know what the future effects will be.

58. Boiling Frog Syndrome