GEOS1100 Lecture Notes - Lecture 6: Sustainable Energy, Viscosity, Stratovolcano
29 May 2018
School
Department
Course
Professor
WEEK 6
LECTURE 1
Management of the Atmosphere - Climate Change
"Climate Change refers to any change in climate over time, whether due to natural variability
or as result of human activity"
• “A catastrophic rise in sea level of 2m is now not beyond the realm of possibility by
2100” (President American Association for the Advancement of Science).
• By 2100 Greenland could be as warm as it was 130,000 year BP when melting ice
raised sea levels by 3-4 m!! (Prof Jonathan Over peck, University of Arizona)
• Current Greenland ice sheet melt is 248 km-3 yr-1 - equivalent to a global sea level rise
of 0.5mm.
• Much of the North Atlantic Ocean is now saturated with CO2 – years ahead of
predictions. As a result, recent IPCC projections of future climate MUST be considered
as conservative.
The Global Climate Record
• The global climate record shows continua change - it’s a composite of cyclic variations
of different frequency
• Detailed knowledge of past climate variability is fundamental
• Knowledge of climate change (spatial and temporal is essential to policy makers,
environmental and resource managers
How does recent climate change compare to that of the past?
• Ice cores offer an unparalleled record of the past climate variability and associated
environmental change
• Ice cores provide excellent geologic archives of climate variability and changes in
atmospheric trace gas concentrations, i.e CO2, CH4 (methane)
• These records show that the rapid increase in greenhouse gases (cO2) monitored over
the last 50 years and the corresponding rate of temperature change has not been
exceeded for at least the last 700ka years.
• Mean Global CO2 concentrations are no at 206ppm which is >30% greater than at
anytime in the past 800,000 years
• The rate of increase is 200 times faster than at anytime over the same period
Is the recent observed warming really a greenhouse effect?
• Greenhouses develop a microclimate largely because of the reduction in cooling airflow
• The basis of the so-called "greenhouse" effect is the ability of certain gases to absorb
longwave radiation emitted from the Earth's surface
Global CO2 emissions
• Global emissions of CO2 continue and are accelerating
• Relative contributions to the enhanced greenhouse effect from pre-industrial times to
2011, due to the long lived green house gases, are: CO2 (64%), CH4 (18%), synthetics
(12%) and N2O (6%)
• Australia produces 1.3% of the global CO2 emissions
Sources and trends in Australian greenhouse gas emissions
• Electricity and heat production, 56.8%
• Agriculture, 20.2%; Transport, 15.9%
• Fugitive emissions, 6.9%; Waste, 3.4%
• Industrial processes, 2.2%
Observed and Predicted Global Climate Change
• Global average surface temperature increased by 0.8 +/- 0.2˚C during the 20th century
• 16 of the 17 warmest years on record have now occurred since 2001 with 2016 the
warmest yeear at 0.99˚c above the mid 20th century mean
• Snow and ice cover has decreased by 10% since 1960
• Global average sea level rose by 0.1 to 0.2m during the 20th century
• There have been significant observed changes in global precipitation and cloud cover
Indicators of a warming world
• Surface temperatures in the Arctic are increasing at a rate about two times faster than
the rest of the world
Observed and Predicted Australian Climate Change
• An increase in average annual surface temperatures of 0.76% over the last 101 years
(1910-2011). Forecast to increase between 0.6 to 1.5˚c by 2030 and 1 to 5˚c by 2070.
• Annual average daily maximum temperatures have increased by 0.75˚c and minimum
temperatures by 1.1˚c (1910-2011)
• Significant warming will occur in the northwest
• Stronger tropical cyclones (20%) that may affect regions further south due to warmer
SSTs
Australian Rainfall
• Australia has been slightly wetter, but the trend is not statistically significant
• Extreme rainfall events have become more common and the frequency of such events is
projected to increase
• Projected changes in precipitation of -10 to +10% by 2030, and -35 to +30% by 2070
• Projected increase in evaporation means greater moisture stress
• Significant uncertainty surrounds El Niño (Drought)
So how warm (hot) will it get?
• Without immediate action to reduce greenhouse gas emissions, the World is likely to
warm by more than 3˚c above the preindustrial climate
• If steps are not taken to reduce emissions immediately a warming of 4˚c is likely by
2060
• A further warming to levels over 6˚c with several meters of sea-level rise, would likely
occur over the following centuries - due to inertia
• The effects of a 4˚c global warming will see the greatest warming over land in the range
from 4˚c to 10˚c
• Increases of 6˚c or more in average monthly summer temperatures would be expected
in large regions of the world
• 4˚c warming would significantly exacerbate existing water scarcity in many regions
• Extremes of rainfall and drought projected to increase globally
• Large scale loss of biodiversity (climate becomes key driver)
• Risk of crossing critical social system thresholds will grow potentially leading to social
unrest, political instability, militancy and possible war
Some more food for thought - a lasting legacy
• The emissions pledges made at the climate conventions in Copenhagen and Cancun, if
fully met, will place the World on a trajectory for a global mean warming of >3˚C
Other issues
• Population Growth >10 billion by 2050
• World food shortages by 2050
• Climate Change driven conflict over access to water resources, breakdown of civil
order resulting from scarcity of food, water.
• Political inaction
• Mass migrations
• Developed v. under developed nations
