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The likely consequences of global climate change
The changes in the atmosphere cause it to retain more heat energy and warm up, but the
actual temperature changes are quite small and they are less than the temperature
fluctuations during the typical day. The mean global temperature has risen about
0.75°C in the last 100 years. Accurate predictions are difficult, but a rise of 1 to 4°C in the
next 100 years seems likely. Even this temperature rise would have relatively small
impacts compared with the indirect effects of changes in other natural processes.
Sea level rise
A temperature rise will cause sea levels to rise in two ways: thermal expansion and
melting land ice.
The warmer atmosphere causes the sea to warm up and therefore expand causing sea
level to rise. This will be a very slow process because there is an enormous amount of
water in the oceans. Water has a high specific heat capacity so it will take a long time for
the temperature of the sea to 'catch up' with the warmer atmosphere and fall all the
expansion to take place. Only water at the surface is warmed by direct contact with the
atmosphere, so deep water will only warm up when the slow-moving ocean currents
bring it to the surface.
Melting land ice
As the Earth warms up ice will melt. Ice that is floating on the sea does not cause sea
levels to rise when it melts as it contracts during melting and occupies the same volume as
the volume of water it displaced when it was ice.
Ice that is on land will cause sea levels to rise as the water flowing into the sea increases the
volume of water in the sea. Glaciers and Antarctic ice shelves form on land and cause sea
level to rise as they flow off the land and displace seawater.
The mean rate of the sea level rise over the last 100years has been 1.7mm per year, mainly
due to thermal expansion and the melting of some glaciers.
Changes in climate
More climate systems are driven by energy from the sin. Retention of energy in the
atmosphere may change the processes involved in these systems.
Winds may change in velocity, frequency and direction. Stronger winds may cause storm
damage. If the direction changes, then the rain that is distributed by the wind may fall in
different areas. So, some areas would get more rain and others would get less.
Higher temperatures would increase evaporation rates, resulting in increased
precipitation rates when the air cool sufficiently. Areas that previously received rain may
get less of it becomes too warm for the water vapour to condense. Areas that were
cold may have received little precipitation in the past as the water vapour condensed
and fell before it reached there. Warming could increase precipitation as the water
vapour could be carried further before it condensed and fell.
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Ocean Current Changes
The ocean currents are a complex interconnected system, largely driven by processes
that occur in the atmosphere. Wind causes surface water to move, evaporation caused
by warming causes water to flow to balance water levels and a change in the density of
surface water caused by heating or cooling would affect the ease with which surface
water sinks. Changes in salinity caused by changes in evaporation or inflow of
freshwater from melted land ice would also affect water density.…read more
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Species may be affected directly by temperature changes or by the other changes that
the temperature rise causes.
Temperature rise may cause plants to grow faster. This could provide more food for
herbivores such as butterflies and moth caterpillars. But many plants produce
toxins that build up in their leaves to protect them from being eaten. If plant
growth begins earlier in the year, then the toxins may build up sooner, which could
kill the caterpillars.…read more