Chapter 2
A Safe Landing for the Climate
A Safe Landing for the Climate
•
The climate has risen 0.7 degrees Celsius.
•
Most of this has occurred in the mid 20th century.
•
Human activities are most likely to be blamed.
•
Most recently, the Arctic has lost much of their ice.
•
The emissions of greenhouse gases are increasing by the increase in the burning of
fossil fuels.
•
It’s expected to raise the Earth’s temperature by another 4-6 degrees Celsius by
the end of this century.
•
If this does happen it will cause a lot of problems.
• In 1992, the United Nations Framework Convention on
Climate Change that was adopted in Rio de Janeiro at
the Earth Summit.
• “The main objective of this Convention is to stabilize
the greenhouse gas concentrations in the atmosphere
at a level that would prevent dangerous anthropogenic
interference with the climate system. Such a level
could be achieved within a time frame sufficient to
allow ecosystems to adapt naturally to climate change,
to ensure economic development to proceed in a
sustainable manner.”
• In 2007, the Intergovernmental Panel on Climate
Change (IPCC) predicted that there would be serious
risks and damages to species, ecosystems, human
infrastructure, and societies in the future unless the
warming is reduced. By reducing the greenhouse gas
emissions it lowers the temperature. To determine
whether it is dangerous or not to the environment
affects the rate, timing, and scale of emission
reductions required regionally and globally. If the
global average temperature exceeds 4 degrees Celsius
above the preindustrial level then there will be an
urgent emphasis on global emissions reductions of 80%
or more by 2050.
•
Water availability and weather extremes have a big impact on humans and the natural system.
•
Precipitation can be expected to decrease also.
•
In many places such as the Mediterranean basin, western United States, southern Africa and
northeast Brazil will have a decrease in water due to the climate changes.
•
The ecosystems that are affected are mountain regions, tundra, tropical forests, and Mediterranean
types are all places where precipitation decreases.
•
Coral reefs and salt marshes live off of sea ice.
•
Both the Arctic and Antarctic have seen a decrease in ice.
•
Such huge loss of ice can threaten the life that lives on it like polar bears.
•
As sea levels rose, they also noticed that there was a relationship between sea levels and
temperature over the last century.
Tipping Points
• There can be plenty of different tipping points if
the earth’s temperature is over 3 degrees Celsius
over the preindustrial level.
• Some examples are Arctic sea ice, the Greenland
ice sheet that would possibly raise the sea level 6
or 7 meters, West Antarctic ice sheet that would
raise it 4 or 5 meter but these are over many
centuries and the Amazon rainforest that could
possibly collapse due to warming and rainfall
reduction.
What Levels Of Warming Might Be
Safe?
• In 1986 the U.N Environment Programme set up an Advisory Group
on Green house gases, which in 1990 reported that a 2-degree
warming Could be “ an upper limit beyond which the risks of grave
damage to ecosystems, and non- linear responses, are expected to
increase rapidly.”
• Warming more than 0.1 degree Celsius per decade was seen as
especially risky to forest ecosystems
• Since 2005 other countries have joined in calling for global mean
warming to be limited to 2 degrees: Chile, Iceland, Norway,
Switzerland, the least developing countries and small island
developing states.
• A safe warming limit would be below 1.3 – 1.4 degrees Celsius
above the preindustrial level.
A Warming of 2 Degrees Celsius is clearly not “safe”
and would not prevent, with high certainty dangerous
interference with the climate system.
• There is no “magic number” lower than 2 degrees Celsius
that would limit warming to safe levels
• Warming in the range of 1.5 -2 degrees Celsius clearly
contains a significant risk of dangerous changes
• Below 1.5 degrees Celsius there is still appears to be a risk
of dangerous changes. Even at 1 degrees Celsius warming
there remains a risk of significant loss of ice from ice sheets
as well as large damages to vulnerable ecosystems.
• It would seem safest to reduce emissions fast enough In the
coming decades so that global warming can be stopped
soon and as far below 2 degrees Celsius.
• Aiming to get it below 1 degrees Celsius above preindustrial
level.

System
1.5 -2.0 degrees Celsius
2.0 -2.5 degrees Celsius
> 2.5 degrees Celsius

Ecosystem and
biodiversity
o
Sharply
accelerated risk
of extinction of
land birds
o
Major losses of
endemic plants
and animals in
the Southhern
Africa, Norther
Australia
o
20 -30% of plant
and animal
species assessed
at increased risk
of extinction

Food and
production
o
Decreases in
cereal production
for some crops in
low latitude
poor regions
o
Significant
decreases in crop
production of
around 5% for
wheat and maize
in India and rice
in China
o
Risk of decline in
crop yield
globally

Coastal regions
o
Increased
damages from
storms and
Floods, with up
to 3 million
additional people
at risk of coastal
flooding
o
Increasing
damages
o
Increasing
damages

Health
o
o

Water
o

Sea level rise
o
Increasing
burden from
malnutrition .
Increased
mortality from
heat waves,
floods, and
droughts
Many
hundreds of
millions at risk
of increased
water stress in
Africa, Asia and
Latin America
Greenland ice
sheet of
irreversible
meltdown for
warming of 1.9
– 4.6 degrees
Celsius
o
Increasing
damages
o
Increasing
damages
o
Increase
numbers at risk
of water stress
o
2 billion at risk
of increased
water stress for
warming over
2-2.5 degrees
Celsius
o
Increasing risk
o
Loss of ice
sheet would
raise sea level
by some 2 -7
meters over
centuries to
millennia
Emission pathways that could limit warming
to “safe” levels
Uncertainties
• Confidence in warming limit
• Higher confidence rating states that certain
damages and risks could be could be
avoided or prevented (climate)
Emission Lifetimes
• Aerosols - days or weeks
– Rapid effect on temperatures
– If all combustion & activities that produce CO2 and lead to production of
aerosols were cut to zero overnight
• Drop in aerosols would yield a sudden loss of their cooling effect
• Sharp warming spike before temperatures declined
• CO2 - 1,000 years or longer
– Cutting these emissions would cause only a slow reduction
– Would most likely require a multi-century, world-wide commitment
The Challenge
• Finding an emissions pathway that is
technically and economically plausible
– No current pathway can bring warming below 1
deg. Celsius
– Few below 1.5 deg. Celsius by 23rd century
• All of these require several of the same things…
Reducing CO2 Emissions
– To reach low stabilization levels of GHG
concentrations, negative CO2 emissions are required
by the last quarter of the twenty-first century at the
latest
– Without negative CO2 emissions, it is impossible to
draw down atmospheric CO2 concentration
– Need global deployment of renewable energy systems
– Deforestation needs to be halted well before 2030
– Extracting CO2 appears to be a necessity that must be
confronted within the next 50 years
Possibilities to Reduce CO2
• Low Stabilization Studies
– Biomass energy with carbon capture and storage
(BECS)
• CO2 is stored underground in stable geological
reservoirs
– Biofuel plantations
• Grow plants that take up CO2 from the air as they grow