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Summary Man & Environment
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Summary Man andEnvironment
DPSIR
Driver: human need, followed by activities that meet this need.
Pressure: The effect of human activity on the environment, like environmental
resources, land use, and emissions to air, water and soil.
State: physical/chemical/biological variables that are influenced by pressure.
Impact: a negative change (health and welfare, and/or ecosystem quality), caused
by a change in states.
Response: human interference in DPSIR chain to prevent or reduce any part of the
chain.
Climate change
IPCC I: the scientific basics of climate change
The climate is warming up and many of the changes in the climate system that
have been observed since the fifties had not occurred in the past hundreds to
thousands of years. The atmospheric concentration of greenhouse gases (GHGs)
has increased, the atmosphere and the ocean have warmed up, the amount of snow
and ice has decreased, and the sea level has risen.
Since 1998, the world’s average increase of temperature has been much
smaller than the decades before. This trend reversal is called a “pause”. Several
natural influences on the climate occurred that compensated for the increased
GHGs that period. These natural influences are only temporary and will nog have a
long-term effect.
It is very likely that humans are the main cause of the warming that has been
observed since the mid-twentieth century.
The observed changes
Greenhouse gases
Concentrations of CO2, CH4 and NO2 have increased to values that have not
occurred in, at least, the last 800.000 years.
[CO2] has increased by 40% since the pre-industrial era. Mostly because of
the burning of fossil fuels, producing cement, and changes in the use of land.
The ocean has absorbed about 30% of human’s CO 2 emission, leading to
acidification of the ocean.
,Temperature
On average, it has become 0.9 °C warmer worldwide in the past 130 years.
With the eighties, nineties and zeroes being the warmest three decades since
1850.
Global warming does occur at a constant rate; it is subject to natural
fluctuations.
The cooling trend that was caused by a change in the inclination of the earth
that should have lasted another thousands of years, has been undone by the
quick warming of the twentieth century.
Since 1951, the temperature in the Netherlands and those around it rose
about twice as fast than globally. This can be partially explained by the wind
coming from the west more often.
Precipitation and humidity
Since 1901, the average precipitation (=neerslag) over land has increased.
Globally the amount of water vapour in the air has increased since the
seventies, because warmer air can contain more humidity.
In the Netherlands, annual precipitation has increased by 26%. All seasons
but summer have become wetter. In coastal areas, the increase of moderate
extremes was the biggest.
The presence of more water vapour in the air has an even larger effect on
heavy storms.
The amount of precipitation per increases with approximately 12% per
degree of warming.
Wind
In the fifties to the nineties, the strength of the wind has increased but has
largely been cancelled out by the recent decrease.
At the beginning and the end of the twentieth century, there were more
storms above the North Sea area. Halfway through the century and in recent
years, the number of storms has decreased.
Above land, there is a steady decrease in wind speed and the number of
storms since the sixties. This looks like an effect of the increased building
intensity in the Netherlands, the wind is slowed down except for the coast
area.
Ocean
Of the extra heat that the climate system has absorbed in the past decades,
over 90% of it is stored in the ocean.
In this period, the upper part of the ocean has warmed.
~30% of the extra absorbed heat has been stored in the deeper ocean.
Ice
In the past two decades, the ice caps of Greenland and Antarctica have
become smaller.
The glaciers worldwide have shrunk further.
The sea ice in the summer and the snowfall have decreased as well.
,Sea level
Since the middle of the nineteenth century, the pace of the rising sea level
has been higher than in the past 2000 years. In addition, in the past years it
has been rising even faster.
The sea level of the North Sea differs yearly because of the variations of the
wind; therefore, there can be no clear acceleration be concluded.
The anthropogenic contribution
Anthropogenic = resulting from the influence of humans.
The anthropogenic influence manifests itself especially in two developments:
1. The warming effect caused by an increase in GHGs.
2. The cooling effects of aerosols.
It is certain that the warming effects of GHGs are stronger than the cooling
effects of aerosols.
The earth cannot easily dispose of the energy it receives from the sun because of
the increase of atmospheric concentration of GHGs. The surface of the earth warms
up until it reaches a new balance between the incoming solar heat and the outgoing
infrared radiation. It takes many years to reach a new balance so global warming
falls behind the increase of atmospheric concentration of GHGs.
Radiative forcing = the difference between solar heat absorbed by the
earth and the energy radiated back to space. The increase of [CO 2] in the
atmosphere contributes the most to radiative forcing.
An increase in aerosols causes more reflection of solar radiation and the effects
have a cooling effect.
Direct effect of aerosols: increased release of energy to the universe.
Indirect effect of aerosols: more aerosols in the atmosphere change the
properties of clouds.
The influence of natural factors on the energy balance, like variations in solar
activity and volcanic eruptions, is small compared to anthropogenic influence in a
time frame in many decades. In a shorter time frame, natural factors can influence
the energy balance.
After a powerful volcanic eruption in the tropic, aerosols are blown up so high
in the atmosphere, they spread all over the world. This increases solar reflection
and therefor it has a cooling effect.
Internal variability = the chaotic interplay between the atmosphere, land, ice,
and oceans lead to fluctuations of the world average temperature.
This plays a relatively minor role in the world average temperature because
these fluctuations are smoothed out over the entire earth.
The anthropogenic influence can be found in the observed warming of the
atmosphere and the ocean, in changes in the global water cycle, in the decrease of
snow and ice, in the global average sea level rise, and in the changes in some
climate extremes.
, Radiative forcers
Effective Radiative Forcing (ERF) = the power of the causes of the changes is
the energy balance quantified as radiative forces in units of (W/m 2).
The increase in the atmospheric concentrations of GHGs caused by
anthropogenic activity leads to an increase in the radiative forcers because it
means that less infrared radiation leaves the earth’s atmosphere.
What more to expect
Not only is the intensity of climate sensitivity of importance for the degree of
climate change but also the expected emission of GHGs, aerosols, and the changes
in land usage.
Because of the great heat capacity of the oceans, it will take some decades
before the temperature rise has reached its full intensity.
Extremely high temperatures will occur more often because of the expected
increase in the average temperatures. Even though the chance of periods of
extreme cold in the winter still exists, the number and duration will decrease.
Global warming causes global changes in the water cycle but these changes
differ from area to area. Wetter area will become wetter, and drier areas will
become drier
The ocean will warm up globally. Transport of the heat from the surface to the deep
ocean will influence the currents in the ocean. And because of the absorption of
CO2, the acidity of the ocean will increase further.
Climate sensitivity
Climate sensitivity = a measure that is defined as the change of the world
average temperature caused by doubling of the CO 2 concentration.
The power of climate sensitivity depends on the feedbacks in the climate
system. Temperature depended processes can reinforce or weaken the global
temperature rise by radiation processes. Especially the hydrological cycle --> water
vapour increases as it becomes warmer --> water vapour is a strong GHG and thus
strengthens (almost doubles) the initial effect of an increase of the CO 2 level.
A positive feedback: warmer world --> decrease in ice coverage --> decrease
the reflecting ability of the earth --> warmer world.
The earth’s energy balance
More GHG emissions --> higher [GHG] in the atmosphere --> more of the infra-red
radiation emitted from the earth is partially re-emitted back to earth by the GHGs --
> increase of temperature.
The earth’s temperature will not continue to keep rising indefinitely after a
certain increase in GHG concentrations changes earth’s energy balance. Because
the earth’s equilibrium will ultimately be restored, as the earth’s new higher
temperature also means that more radiation is emitted.
These express the climate change effect of GHGs:
Radiative forcing (W/m2) = the difference between incoming radiation from
the sun and outgoing radiation from the earth that is caused by the presence
of change concentration of a GHG. When outgoing radiation is lower than
incoming radiation (because outgoing radiation is partly “trapped” by GHGs),
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