- GREENHOUSE EFFECT:
All forms of electromagnetic energy can excite molecules and make them move faster, creating heat.
If light or other electromagnetic energy enters a greenhouse, the heat energy is trapped inside the greenhouse and cannot escape.
This warms the greenhouse, producing a greenhouse effect.
Earth's atmosphere acts like a greenhouse. Electromagnetic energy from the sun excites the molecules in the atmosphere and causes them to move faster, creating heat.
This traps heat within the atmosphere, producing a greenhouse effect.
Some molecules in the atmosphere, like CO2, contribute more than others to the greenhouse effect.
A few molecules, like methane, have a much larger per-gram greenhouse effect, but their quantities are so low that we usually ignore them.
The greenhouse effect warms the planet and is the major reason for global warming.
- CARBON DIOXIDE POLLUTION:
Scientists who measure climates of the past (see Topic 91) have concluded that
temperatures of the past have always gone up with higher CO2 concentrations and down with lower CO2 concentrations.
Since the 1950s, Nobel Prize-winning scientist Charles Keeling has been measuring CO2 concentrations at Mauna Loa Observatory on Hawaii.
This location is in the middle of the Pacific, far from any industrial source of pollution, and is widely thought to represent global averages of CO2 concentrations.
Keeling's measurements show that CO2 concentrations go up and down seasonally (lower in summer,
when plant photosynthesis removes more CO2 from
the atmosphere, and higher in winter),
but the overall year-to-year trend has been steadily upward since the 1950s !
Global average temperatures have also been rising steadily over this same time period. In most places, the hottest years on record are mostly the recent ones.
Most scientists attribute the rise in CO2 concentrations to the release of combustion products (mostly from the use of fossil fuels),
and the increase in global average temperatures to the greenhouse effect.
- Feedback effects:
As temperatures rise, the melting of polar ice lowers the planet's albedo, meaning that more solar energy is absorbed
by the dark-colored rocks and soil
instead of being reflected out to space by the ice. This contributes to more global warming.
The melting of polar ice also releases significant quantities of methane gas and complex methane compounds (clathrates) frozen inside.
Although the quantites are small, methane is a very potent greenhouse gas, several hundred times as strong as CO2 in
contributing to the greenhouse effect.
As temperatures rise, forest fires are becoming more frequent, larger, and harder to contain. Forest fires contribute to the
rise in atmospheric CO2.
The loss of forest vegetation also contributes to higher CO2 concentrations
because plant photosynthesis no longer removes CO2 from the atmosphere.
All of the above contribute to feedback: increased global warming contributes to even more global warming!
- Other consequences:
As global temperatures rise, more polar ice melts, and this contributes to rising sea levels.
In 2019, an iceberg the size of Delaware broke off Antarctica and began to drift toward
warmer waters, where it will eventually melt and add to global sea rise.
Similar icebergs, large and small, are breaking off the edge of both Greenland and Antarctica at increasing rates.
As carbon dioxide contrations rise, more of it dissolves in sea water and forms carbonic acid, making the waters more acidic.
This ocean acidification contributes to the death of corals. Colorful coral reefs turn white, and this is called coral bleaching.
And it isn't just the corals: coral reefs are the most diverse aquatic habitats on the planet, containing a larger fraction
of biodiversity than any other aquatic habitat!
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