produce more intense precipitation events,
increasing the risk of flooding. The higher amount
of moisture in the air will also result in stronger
moisture transport between dry and wet regions,
generally resulting in dry areas becoming drier
(e.g., in subtropics – increased risk of droughts)
and wet areas becoming wetter (e.g., in tropics
and extratropics – increased risk of flooding)
[189]. However, with a warming climate, atmospheric circulation patterns are also expected to
change (e.g., Hadley cell expansion, poleward
movements of jet streams, changes in stationary
waves) and with it regional precipitation patterns
[190] (see below).
Hadley Cell, Jet Streams, Storms, and Rainfall
Distribution
One of the predicted atmospheric circulation
changes under climate change is the expansion
of the Hadley cell [29]. Work by Hu and Fu has
shown that the Hadley cell has already expanded
significantly, between 2 and 4.5
of latitude, since
1979, especially during the summer and fall. This
implies a poleward shift of the subtropical dry
zone, leading to less precipitation in regions poleward of the current/past subtropical zone
[29]. This means that the effect of the circulation
changes is that areas with currently sufficient
amount of rainfall can become drier with global
warming and vice versa, as well as to potentially
further enhance the wet-gets-wetter and dry-getsdrier patterns (mentioned above).
With warmer atmosphere and oceans, there
will also be more energy available for storm
growth, potentially leading to intensification of
tropical and extratropical cyclones and associated
stronger winds, storm surges, and precipitation.
The different distribution of heat across the
Earth’s surface and upper layers of the atmosphere
will also lead to different distributions of these
storms in a warming climate.
Extratropical cyclones, distinct from tropical
cyclones (i.e., hurricanes and typhoons), are
formed by large mid-latitude surface temperature
gradients, for example, in the North Atlantic,
North Pacific, and Southern Oceans and the Mediterranean Sea [27]. Generally, extratropical
cyclones contribute to rainfall, winds, and thermal
fluxes in these regions, while the direction and
speed of extratropical cyclones are affected by
the jet stream. Therefore, the distribution of precipitation is related to the course of the jet stream.
Generally, the jet streams are predicted to move
poleward with climate change [27], moving
storms poleward from their current positions and
leaving less storms where they’re currently
located. This will result in more precipitation
from extratropical storms poleward from current
precipitation bands and less precipitation equatorward. Changes to the meandering of the jet stream
(i.e., changes to stationary waves) will further
contribute to the changes in precipitation patterns.
These effects have important implications for
water resources (via rainfall redistribution) in
these regions as a consequence of climate change;
one example is the drying of the Mediterranean,
which largely results from drier cold season in the
region [28].
Soil Carbon Content and Permafrost
Soils store carbon, and the rate of decomposition of
soil organic matter depends on temperature
[37]. With climate change the flux of CO 2 from
soils will also increase, simultaneously depleting
soil carbon. In Arctic and sub-Arctic regions, large
quantities of organic carbon, twice as much carbon
as there is the atmosphere [38], are trapped in frozen
soils as permafrost. Permafrost carbon is derived
from plants and animals that have accumulated in
permanently frozen soil over thousands of years.
Human activities in northern regions cause local
climate warming as well. Over the last 30 years,
the temperature has risen 0.6
C per decade in highlatitude regions [10], causing frozen ground to thaw
[39]. When organic carbon is exposed to soil
microbes, it decomposes releasing methane and
CO 2 . This positive feedback accelerates climate
change, but the magnitude and timing of greenhouse
gas emissions from these regions and their impacts
on climate change remain uncertain.
Consequences of Climate Change: The Sixth
Mass Extinction
There have been five historical/geological mass
extinction events in the history of our planet, the
last one occurring roughly 65 million years ago
292
Air Pollution and Climate Change: Sustainability, Restoration, and Ethical Implications
increasing the risk of flooding. The higher amount
of moisture in the air will also result in stronger
moisture transport between dry and wet regions,
generally resulting in dry areas becoming drier
(e.g., in subtropics – increased risk of droughts)
and wet areas becoming wetter (e.g., in tropics
and extratropics – increased risk of flooding)
[189]. However, with a warming climate, atmospheric circulation patterns are also expected to
change (e.g., Hadley cell expansion, poleward
movements of jet streams, changes in stationary
waves) and with it regional precipitation patterns
[190] (see below).
Hadley Cell, Jet Streams, Storms, and Rainfall
Distribution
One of the predicted atmospheric circulation
changes under climate change is the expansion
of the Hadley cell [29]. Work by Hu and Fu has
shown that the Hadley cell has already expanded
significantly, between 2 and 4.5
of latitude, since
1979, especially during the summer and fall. This
implies a poleward shift of the subtropical dry
zone, leading to less precipitation in regions poleward of the current/past subtropical zone
[29]. This means that the effect of the circulation
changes is that areas with currently sufficient
amount of rainfall can become drier with global
warming and vice versa, as well as to potentially
further enhance the wet-gets-wetter and dry-getsdrier patterns (mentioned above).
With warmer atmosphere and oceans, there
will also be more energy available for storm
growth, potentially leading to intensification of
tropical and extratropical cyclones and associated
stronger winds, storm surges, and precipitation.
The different distribution of heat across the
Earth’s surface and upper layers of the atmosphere
will also lead to different distributions of these
storms in a warming climate.
Extratropical cyclones, distinct from tropical
cyclones (i.e., hurricanes and typhoons), are
formed by large mid-latitude surface temperature
gradients, for example, in the North Atlantic,
North Pacific, and Southern Oceans and the Mediterranean Sea [27]. Generally, extratropical
cyclones contribute to rainfall, winds, and thermal
fluxes in these regions, while the direction and
speed of extratropical cyclones are affected by
the jet stream. Therefore, the distribution of precipitation is related to the course of the jet stream.
Generally, the jet streams are predicted to move
poleward with climate change [27], moving
storms poleward from their current positions and
leaving less storms where they’re currently
located. This will result in more precipitation
from extratropical storms poleward from current
precipitation bands and less precipitation equatorward. Changes to the meandering of the jet stream
(i.e., changes to stationary waves) will further
contribute to the changes in precipitation patterns.
These effects have important implications for
water resources (via rainfall redistribution) in
these regions as a consequence of climate change;
one example is the drying of the Mediterranean,
which largely results from drier cold season in the
region [28].
Soil Carbon Content and Permafrost
Soils store carbon, and the rate of decomposition of
soil organic matter depends on temperature
[37]. With climate change the flux of CO 2 from
soils will also increase, simultaneously depleting
soil carbon. In Arctic and sub-Arctic regions, large
quantities of organic carbon, twice as much carbon
as there is the atmosphere [38], are trapped in frozen
soils as permafrost. Permafrost carbon is derived
from plants and animals that have accumulated in
permanently frozen soil over thousands of years.
Human activities in northern regions cause local
climate warming as well. Over the last 30 years,
the temperature has risen 0.6
C per decade in highlatitude regions [10], causing frozen ground to thaw
[39]. When organic carbon is exposed to soil
microbes, it decomposes releasing methane and
CO 2 . This positive feedback accelerates climate
change, but the magnitude and timing of greenhouse
gas emissions from these regions and their impacts
on climate change remain uncertain.
Consequences of Climate Change: The Sixth
Mass Extinction
There have been five historical/geological mass
extinction events in the history of our planet, the
last one occurring roughly 65 million years ago
292
Air Pollution and Climate Change: Sustainability, Restoration, and Ethical Implications