The Changing Climate
- The Climate System
- Is Our Climate Changing?
- past climates have changed at all time scales from decades
to millions of years.
- research on human activities shows that humans are changing
the earth's climate.
- there is evidence that world climate has become more
- Detecting Climate Change
- Evidence From Seafloor Sediments (JOIDES
Resolution). The numbers and types of organisms living near the surface
change with the climate.
- Evidence From Oxygen Isotope Analysis. Ratio between
16O and 18O in glacial ice and shell fragments in
- Evidence Form Other Sources
- Natural Causes of Climate Change
- Plate Tectonics and Climate Change
- Volcanic Activity and Climate Change
- Mt. Tambora, Indonesia in April 1815 largest
eruption of modern times expelled more than 24 cubic miles of volcanic
debris. The summer of 1816 saw snow storms in June in the NE US as well as
frost in July and August.
- Mt. Etna
- Mt. St. Helens - no
measurable climate change.
- El Chichon - 1982, increased global temps about
0.5 - 0.9oF
- Mt. Pinatubo - 1991, ejected 25-30 million tons
of sulfur dioxide. Lowered global temps by 0.9oF during the
- Orbital Variations
- Solar Variability and Climate
- Sunspots (close
up) and Temperature - lack of sunspots correlated with colder temps in
N. America and Europe and plentiful sunspots correlated with warmer times
in these regions.
- Mean Annual Sun Spot
- Sunspots and Drought
- Human Impact on Global Climate
- Carbon Dioxide, Trace Gasses and Climate Change
- Climate Feedback Mechanisms
- How Aerosols Influence Climate
- Some Possible Consequences of Global Warming
- Feedback Mechanisms - natural systems have
mechanisms enhance or resist change
- negative feedback mechanisms - work to maintain
the system. For example, when we get too hot, we perspire to cool down.
- positive feedback mechanisms enhance change.
- tipping point - a point where small changes suddenly
give way to a sudden and self-perpetuating changes. For example, pump enough
CO2 into the atmosphere, and that last part per million of
greenhouse gas behaves like the 212th degree Fahrenheit that turns a pot of
water into a plume of billowing steam.
Examples of possible global warming tipping points:
- Recent measurements indicate several Greenland ice sheets
have doubled their rate of slide.
- Greenland ice is not just melting
but doing so more than twice as fast, with 53 cu. mi. draining away into the
sea last year alone, compared with 22 cu. mi. in 1996. A cubic mile of water
is about five times the amount Los Angeles uses in a year.*
- An April 2006 article in Science suggests that by
the end of this century, the world could see as much as a 20 foot rise in sea
"Things are happening a lot faster than anyone
predicted," says Bill Chameides, chief scientist for the advocacy group
Environmental Defense and a former professor of atmospheric chemistry.
- Last ice age CO2 concentrations were just 180
p.p.m. putting the earth into a deep freeze.
- After the glaciers retreated and just before the dawn of
the modern era, the concentrations had risen to a comfortable 280 p.p.m.
- IN just the past 150 years we have pushed the level to 381
p.p.m. and feeling the effects.
- Of the 20 hottest years on record, 19 occurred in the 1980s
- According to NASA scientists, 2005 was one of the hottest
years in more than a century.
- Polar ice cap melting. Ice reflects 90% of the
energy that strikes it. Ocean water does the opposite, absorbing most of the
energy that reaches it. The more energy the water retains the warmer it gets,
with the result that each mile of ice that melts vanishes faster than the mile
that preceded it.
Remove the North Polar ice cap and the comparatively warm water beneath begins
to release its heat to the atmosphere accelerating global warming.
- Permafrost melting. Permafrost contains a lot of
partially decayed organic matter, rich in carbon. In high-altitude regions of
Alaska, Canada and Siberia, the soil is warming and decomposing, releasing
methane and CO2. That, in turn, will lead to more global warming.
How much carbon is stored in the permafrost soils? 200-800 gigatons. The total
human carbon output is only 7 gigatons per year.
- Warmer oceans, colder continents. The Gulf Stream
keeps Europe relatively mild. At the end of the last ice age, the warm current
was temporarily blocked and temperatures in Europe fell 10oF.
locking the continent in glaciers.
Warm Gulf Stream water floats over colder water until it gives up heat to the
atmosphere near Europe where it sinks and returns to the tropics.
Freshwater melt from the Arctic and Greenland ice dilutes the saltwater and
keeps it at the surface, turning off the return flow. Europe gets colder.
- Drought. In the North America west people, animals
and plants make it through the summer thanks to snowpack that melts slowly
during the summer. Lately, the early arrival of spring and blistering summers
have caused the snowpack to melt too early.
Areas around deserts such as the Sahel, experience warmer temperatures that
bake the soil causing desertification.
- Flora & Fauna. Wildfires in Indonesia, the
western US and even inland Alaska have been increasing as timberlands and
forest floors become parched. The blazes create a feedback loop of their own,
pouring more carbon into the atmosphere and reducing the number of trees,
which inhale CO2 and release oxygen.
- What about us? We're suffering destruction of
habitat too. Ocean temperatures have warmed by a full degree F since 1970, and
warmer water is rocket fuel for hurricanes.
Two studies in 2005 found that in the past 35 years the number of Category 4
and 5 hurricanes worldwide has doubled while the wind speed and duration of
all hurricanes has jumped 50%.
- What can we do?
- The US has 5% of the world's population and produces 25% of
the world's CO2 emissions.
- Sign the Kyoto Protocol that pledges countries to reduce CO2