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Notes Chapter 19.1 – 19.2 APES
19.1 How Is the Earth’s Climate Changing?
Weather and climate are not the same:
• Weather = short-term changes to temperature, air pressure, precipitation, and wind
• Climate = average conditions in a particular area over a long period of time based on
temperature and precipitation patterns. This is the section climatologists study to see any
changes within global atmospheric conditions and usually look within at least a 30 year span.
- Two main categories climatologists look within the time span are fluctuating patterns
in average temperature and precipitation each year
Climate change has accelerated:
• Since 3.5 billion years the climate has been altered by major natural sources from:
- Volcanic emissions, changes in solar input (solar radiation near the surface), movement
of continents and meteor impacts.
• Minor natural sources are:
- Global air circulation, large ice sections reflecting solar energy (help cool planet),
various concentrations of gasses in atmosphere, and changes in ocean currents
• Once again these impact temperature and precipitation globally with temperature being the
key to our planets overall climate due to the stress it has on various ecosystem services
• Since 900,000 years glacial and interglacial periods altered climate by having periods of global
cooling and global warming (done naturally)
• Since 10,000 years ago within the interglacial period, temperatures have been roughly stable.
• For the past 1,000 years, average temperatures near the Earth’s surface has remained fairly
stable but:
- In 1975 when:
- Increase in fluctuating temperature changes due to an exponential increase in
population, large amounts of deforestation, and the beginning and continued
use of burning fossil fuels:
- Happening at an accelerated rate
Able to estimate past temperature changes using:
• Radioisotopes in rocks and fossils, plankton and radioisotopes in ocean sediment, tiny
bubbles/layers of soot/other material trapped in different layers of ancient air found in ice cores
from glaciers, pollen from bottoms of lakes and bogs, and tree rings
- Show general changes in atmospheric temperatures, which can therefore show
altercations in earth’s climate
World Bank and NASA 2012 report findings:
- 1906 - 2012 global surface temperature has risen by about 0.8⁰C. Land warms more than
ocean waters due to less transfer of heat in lower layers and warm air remains at surface while
some warm air is transferred into the oceans
- Glaciers are melting at an alarming rate (worry more about since glaciers are land based ice
only)
- Floating arctic sea ice is shrinking at an alarming rate (important but don’t worry as much
about since this is ice that is already contained in water)
- During 20th century average sea levels rose by 7.6 inches based on warmer ocean temps.
19.2 Why Is the Earth’s Climate Changing?
Natural greenhouse gases play a key role in climate:
- Greenhouse gases (CO2, CH4, N2O, water vapor) absorb heat radiated by the earth
• The gases then absorb and retain infrared radiation that warms the atmosphere.
- Molecules of these gases vibrate and cannot escape stratosphere due to the
blocking of these greenhouse gases, which in term are forced to remain in
troposphere and with the remaining infrared radiation continue to warm our
planet
• Top 3 gases are nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) along
with water vapor
- Can’t live completely without greenhouse gases as long as they are natural
• Without them, we would have a cold, uninhabitable earth
Lifetime of atmospheric greenhouse gases:
Potential atmospheric warming from greenhouse gases:
Human activities play a key role in atmospheric warming:
- Since the Industrial Revolution:
• Three main greenhouse gases have been higher due to these anthropogenic sources:
- CO2 = Burning of fossil fuels, clearing of carbon sinks like ancient forests and
phytoplankton, industrial plants
- CH4 = Excess livestock production (feedlots), natural gas production, landfills,
excess algae growth in reservoirs behind manmade dams
- N2O = Excessive nitrogen based fertilizers, burning of fossil fuels (car
emissions), industrial plants
- Correlation of rising CO2 and CH4 with rising global temperatures:
- Average atmospheric concentrations of CO2 rose from 280 ppm to 400 ppm since Industrial
Revolution
- 70% of CH4 emissions over the last 275 years are a result from human activities (probably even
shorter than this)
- Since 2010, U.S. and China accounted for 41% of the world’s greenhouse gas emissions
- Overall, global temperature fluctuation is heavily dependent on human factors that can either
amplify or dampen these changes. An increase in CO2 within the air therefore traps solar
radiation and thus increase surface level temperatures as a direct correlation
What role does the sun play:
- Plays key role in earth’s temperature
- Believe atmospheric warming is not due to an increase in energy output from the sun since our
suns energy is decreasing in energy output but happening more from:
• Tropospheric warming due to greenhouse gasses
• Reverse effect of stratospheric cooling
- Researchers believe a hotter sun should warm stratosphere and not cool it
What role do the oceans play in climate disruption?
- CO2 is soluble in ocean water (through carbon cycle)
• Helps moderate the earth’s average surface temperatures and climate
• Absorb heat from the troposphere as well.
- Along with the heat and CO2 absorbed from troposphere, ocean currents
(upwellings) drive the heat and CO2 into deeper parts of the ocean
- However, if ocean temperatures rise too much (tipping point):
• Absorb less CO2 = hasten atmospheric warming near surface
• More CO2 in ocean that is not dissolving = more acidity (carbonic acid)
• Higher acidity = more strain on marine ecosystems (would have to adapt to survive)
There is uncertainty about the effects of cloud cover on atmospheric warming:
- Warmer temperatures = increase evaporation = more clouds that can cool or warm
atmosphere:
• Think, low and thick altitude cumulus clouds = decrease surface temperatures
• However, with more CO2 in the atmosphere there is a possibility of decrease in
thickness of clouds
- Clouds being predominately thin, cirrus types at high altitudes = increase in
surface temperatures (more radiation to pass through stratosphere into
troposphere)
How can outdoor air pollutants (aerosols) slow atmospheric warming?
- Increase in particulates of sulfur based compounds and SO2 can reflect incoming sunlight and
cool the lower atmosphere