Answer to Question 1
Several changes are already occurring in the oceans due to global warming. Most of the increased heat in the atmosphere has been absorbed by the oceans, so it is not surprising global surface temperatures have risen by about 0.6C since 1970. Subsurface waters also are experiencing higher temperatures. Other changes include the melting of polar ice, changes in deep-ocean circulation patterns, rising sea level, and increases in ocean acidity, with corresponding changes in primary and secondary production.
Answer to Question 2
Several gases released by human activities into the atmosphere cause an enhanced greenhouse effect, including carbon dioxide, methane, nitrous oxides, and CFCs. Of these, carbon dioxide currently has the greatest concentration and the second greatest rate of increase (next to methane). Although carbon dioxide has a lower infrared absorption capability (on a per mole basis) compared to other greenhouse gases, it is the most abundant and thus has the greatest relative contribution to increasing the greenhouse effect. Methane concentration is increasing the fastest of these gases and has 25 times the infrared radiation absorption of carbon dioxide, but is currently three orders of magnitude lower in concentration. CFCs used as refrigerants and propellants have a disproportionately large absorptive effect, but are either stable or decreasing in concentration. Nitrous oxides are thought to be about 5 of the relative contribution to the increasing greenhouse effect.
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