Human threats to the global climate system (Synoptic topic) Flashcards
What are the main drivers of deforestation
-The main driver of deforestation is the increasing
demand for commodity production.
- Soy,
- Palm oil
- Beef
- Paper production
Explain the impacts of deforestation on the water and carbon cycle
Water Cycle
- Reduced intercepted rainfall storage by plants;
infiltration to soil and groundwater changes
- Increased raindrop erosion and surface run-off, with
more sediment eroded and transported into rivers
- Increased local downwind – aridity from loss of
ecosystem input into water cycle through
evapotranspiration
Carbon Cycle
- Reduction in storage in soil and biomass, especially
above ground
- Reduction of CO2 intake through photosynthesis flux
- Increased carbon influx to atmosphere by burning
and decomposing vegetation
How is grassland conversion threatening the global climate system
- The carbon and water cycles are disrupted in
grasslands that are used too intensively for animals
or when ploughed up - Rapid increases in population, coupled with the
effects of climate change and poor management are
the drivers of change
How is ocean acidification threatening the global climate system
- Oceans are an important carbon sink, but their
function as a fossil fuel gas sink is increasingly
changing their overall pH and acidifying them
- Since the industrial revolution – the pH of the
surface sea water has decreased by 0.1, a 30% drop - Ocean acidification refers to the PH of the ocean
due to the uptake of carbon dioxide of carbon
dioxide from the atmosphere. - The ocean’s role as a carbon sink is increasing due
to surges in fossil fuel combustion which has
caused a decline in the health of coral reefs and
other marine ecosystems - Acidification increases the risk of marine ecosystems
reaching a critical threshold of permanent damage - The Arctic Ocean is likely to be the first affected
because of its low pH, threatening vulnerable ‘cold’
corals - Major functions of the ecosystem, especially reef
building, may collapse and this would lead to an
irreversible changed state and net reef loss by the
mid-twentieth century if current levels of carbon
emissions continue
How carbon Climate threatening the global climate system
- There is now unequivocal evidence of humans
triggering the enhanced greenhouse effect with
resulting climate changes - 2015 was an exceptional year for climate change as
it was the first full year to exceed the key benchmark
for global warming of 1 degree above pre-industrial
levels - Many parts of the world experienced unusual
weather patterns e.g. severe droughts in parts of
Africa and severe flooding in parts of India and
Pakistan - May lead to a shift in climate belt – the different
climate zones such as equatorial, tropical, temperate
and polar are not static and warming of more than 2
degrees could lead to five percent of the Earths land
area shifting to a new climate zone
Amazon Rainforest (Changing Climate Case Study)
- The Amazon rainforest acts as a global and regional
regulator, pumping 20 billion metric tonnes of water
into the atmosphere daily - The forests uniform humidity lowers atmospheric
pressure, allowing moisture from the Atlantic Ocean
to reach further inland areas without forest cover - However, since 1990, a more extreme cycle of
drought and flood has developed in the Amazonia,
with wetter rainy season, linked to shifts in the ITCZ - The rainfall has appreciably decreased downwind of
deforested areas, Sao Paolo suffered a water crisis - Therefore, the regional water cycle has been altered
What are the positive impacts of rainforests
- Deforestation affected an estimated 13 million hectares
of forests per year between 2000 and 2010
o Forests provide: food, fresh water, wood and fibre, fuel e.g. 1.1% of global economy income – improve food and nutrition security – 13.2 million formal jobs and 41 million informal jobs
o Regulation of Earth systems: water purification and regulating climate, floods and disease
o Cultural value: direct reliance by many indigenous peoples, some cultures and religions are sacred – leisure and tourism
What is the Kuznet curve
- The Kuznets curve suggests societies reach a
tipping point where exploitation changes to more
protection - Factors affecting this are
• Wealth of a country
• rising knowledge of the role the environment plays in
human well-being
• AID given to poorer nations to help choices over
exploration
• Power of political system, locals and TNCs
The Arctic (Impact of rising temperatures case study on the carbon and water cycle)
- The Earths cryosphere as already been affected by
global warming – over the last 20 years the Antarctic
and Greenland have been losing mass - The Arctic is an early warning system for the rest of
the planet, acting as a barometer of the
environmental impact resulting from fossil fuel
climate forcing
Effects on Water Cycle
- Warm water flowing into the Arctic from the Pacific
and Atlantic - Rising local air temperatures
- Shrinkage of sea ice
- Run-off of fresh cold water will alter marine
ecosystems dependant on the saline waters
Effects on Carbon Cycle
- Methane from destabilisation of wetlands and sea
floor deposits containing methane hydrate, - Mainly methane and some CO2 from thawing
permafrost
Methane
A greenhouse gas that is 25 times more powerful than carbon dioxide
How is loss of Albedo threatening the global climate system
- Albedo is a measure of how sunlight is reflected
away from the Earth’s surface - Ice has a high reflectivity index, so a reduction in the
amount of sea ice may create a positive feedback
loop - Melting allows more heat absorption, causing more
melting - Loss of reflective cooling albedo is from: less
summer ice and the replacement of the tundra with
darker forests as they advance northwards
Explain the IPCC ‘Strong Mitigation Model’
Strong mitigation model
- Mean temperature rise projected to be between 1.5
and 2 degrees by the end of the 21st century - The average warming for land regions is 2.3
degrees, compared to global average of 1.8 degrees - Many regions will experience much greater
increases in temperature still; the Arctic is likely to
have increases of 8 degrees by 2100
Explain the IPCC ‘Business as Usual Model’
Business as usual Model
- This is where we continue to use fossil fuels with no
mitigation - Emissions continue to rise, so global temperature is
predicted to reach 5.6 degrees above pre-industrial
level - Some regions are predicted to warm more than 15
degrees e.g. the arctic - The likely costs of such a scenario are likely to be
large and costly
What impact could climate change have on ocean health and how could this effect civilisations
- The WWF warns that climate change is affecting
ocean temperatures, the supply of nutrients, food
chains, wind systems, ocean currents and extreme
events such as cyclones - The changes may be categorised under: bleaching,
acidification, rising sea levels and loss of sea ice - These changes then affect the distribution,
abundance, breeding cycles and migration of the
marine plants and animals that millions of people
directly and indirectly rely on food for income - Fishing supports 500 million people, 90 per cent of
whom are in developing countries - Fish is also the cultural choice of many wealthier
countries such as Iceland and Japan, but it is an
absolute necessity in poorer countries such as
Namibia, Ghana and Senegal - Countries that depend on exports of their fish
recourse, such as China and Thailand will be
affected by depleted and stunned stocks
What is ‘Climate Uncertainty’
Predictions are uncertain because changes to the climate have several causes and feedback mechanisms. Increasing GHGs, changes in volcanic aerosols and ozone levels all cause circulation changes in models of the atmosphere
