cooling of atmosphere is due to additional absorption and emission of infrared
radiation (Allan 2011). Intense rainfall is mostly local, but it is fed by an atmospheric moisture supply that may deplete other regions from localized moderate
rainfall. These are principles that must be throughout evaluated, because of the
implications for flooding and drought in the future.
Global processes such as latent energy release during storms, or limitations of
moisture sources, can be crucial to the development of distinct regional tendencies
concerning the dependency of rainfall intensity with air temperature. Atmospheric
aerosols modulate the energy balance in the atmosphere and the Earth’s surface
system, thereby influencing these processes (e.g., Allan 2011).
From 1900 to 2005, accumulated precipitation and frequency and intensity of
heavy precipitation events increased significantly in the eastern parts of North and
South America, Northern Europe, and Northern and Central Asia. On the other
hand, precipitation declined in the Sahel, the Mediterranean, Southern Africa, and
parts of Southern Asia. Globally, the area affected by drought has likely increased
since the 1970s (e.g., AR4 and AR5 Reports).
The global water cycle is also likely affected by anthropogenic factors that
influence atmospheric moisture content, changes in precipitation patterns over land,
and the occurrence of heavy precipitation events. The global specific humidity has
very likely increased in the near-surface boundary layer since the 1970s.
In the twenty-first century, the forecasted global changes in precipitation will not
be uniform. The information available since 1901 and particularly 1951 onwards
points to an increase in the average precipitation in mid-latitude land areas of the
Northern Hemisphere. Fisher and Knutti (2015) mention available models predicting heavy precipitation days for Northern Europe and North America, in
response to increasing global temperature.
High and equatorial latitudes, especially in the Pacific and Africa, are likely to
face increases in average precipitation ranging from about 30 to 50% under the
extreme RCP2.6 to RCP8.5 scenarios. In most dry regions in mid-latitudes, mean
rainfall will likely decrease from 5 to 40% under the two extreme scenarios. In
contrast, in mid-latitude wet regions, mean precipitation will likely increase by a
similar range from 5 to 30% under the two extreme scenarios. Under profile
RCP8.5, in dry regions, the frequency of droughts will likely increase toward the
end of the twenty-first century.
Systems likely to be affected by climate change include, among others, the
tundra, and the boreal forest due to the inability to adjust to warming. Negative
impacts due to the lack of precipitation and water availability will cause hydrological negative impacts in areas as diverse as Mediterranean-type ecosystems,
tropical rainforests, and in lower latitude agriculture areas. Also, sea-level rise and
human health downgrading in populations with low adaptative capacity will be
expected. Even in economically well-off areas, some activities, and vulnerable
people, including the poor, young, and elderly, will be at risk.
8.3 Alternative Scenarios for Climate …
281
radiation (Allan 2011). Intense rainfall is mostly local, but it is fed by an atmospheric moisture supply that may deplete other regions from localized moderate
rainfall. These are principles that must be throughout evaluated, because of the
implications for flooding and drought in the future.
Global processes such as latent energy release during storms, or limitations of
moisture sources, can be crucial to the development of distinct regional tendencies
concerning the dependency of rainfall intensity with air temperature. Atmospheric
aerosols modulate the energy balance in the atmosphere and the Earth’s surface
system, thereby influencing these processes (e.g., Allan 2011).
From 1900 to 2005, accumulated precipitation and frequency and intensity of
heavy precipitation events increased significantly in the eastern parts of North and
South America, Northern Europe, and Northern and Central Asia. On the other
hand, precipitation declined in the Sahel, the Mediterranean, Southern Africa, and
parts of Southern Asia. Globally, the area affected by drought has likely increased
since the 1970s (e.g., AR4 and AR5 Reports).
The global water cycle is also likely affected by anthropogenic factors that
influence atmospheric moisture content, changes in precipitation patterns over land,
and the occurrence of heavy precipitation events. The global specific humidity has
very likely increased in the near-surface boundary layer since the 1970s.
In the twenty-first century, the forecasted global changes in precipitation will not
be uniform. The information available since 1901 and particularly 1951 onwards
points to an increase in the average precipitation in mid-latitude land areas of the
Northern Hemisphere. Fisher and Knutti (2015) mention available models predicting heavy precipitation days for Northern Europe and North America, in
response to increasing global temperature.
High and equatorial latitudes, especially in the Pacific and Africa, are likely to
face increases in average precipitation ranging from about 30 to 50% under the
extreme RCP2.6 to RCP8.5 scenarios. In most dry regions in mid-latitudes, mean
rainfall will likely decrease from 5 to 40% under the two extreme scenarios. In
contrast, in mid-latitude wet regions, mean precipitation will likely increase by a
similar range from 5 to 30% under the two extreme scenarios. Under profile
RCP8.5, in dry regions, the frequency of droughts will likely increase toward the
end of the twenty-first century.
Systems likely to be affected by climate change include, among others, the
tundra, and the boreal forest due to the inability to adjust to warming. Negative
impacts due to the lack of precipitation and water availability will cause hydrological negative impacts in areas as diverse as Mediterranean-type ecosystems,
tropical rainforests, and in lower latitude agriculture areas. Also, sea-level rise and
human health downgrading in populations with low adaptative capacity will be
expected. Even in economically well-off areas, some activities, and vulnerable
people, including the poor, young, and elderly, will be at risk.
8.3 Alternative Scenarios for Climate …
281