Climate change - Climatology Flashcards
Ice ages have oscillations of what periods
Glacial (cold) and interglacial (warm) periods
Forcing categories that control the average state of the climate system
External and internal
External forcing involves
Solar variability and astronomical effects
Internal forcing involves
Tectonic processes, volcanic eruptions, aerosols, radiative forcings
How does the sun influence external forcing
Sun changes brightness and solar variability by changes in its mass
Milankovitch cycles
Astronomical controls on solar output
The three inter-related changes that cause long-term variations in solar output
- Eccentricity - how elliptical the earth’s orbit is (aphelion and perihelion)
- Obliquety - the tilt of the earth’s axis of rotation (more tilt in summer/winter)
- Precession - the timing of the equinox (seasons) in relation to its revolution around the sun (caused by earth wobbling slightly on axis)
Changes in eccentricity, obliquity and tilt occur in what timespan
23,000-100,000 years
How does tectonic plate processes affect global processes in terms of internal forcing
- They affect ocean circulation and atmospheric processes (continental drift)
- Associated with chemical processes resulting in large carbon release
- Presence of mountain ranges creates orogenesis
How does volcanism affect global processes in terms of internal forcing
Large volcanic events launch dust into the atmosphere which leads to greater scattering and reflection of solar radiation - cooling effect
How do atmospheric aerosols affect global processes in terms of internal forcing
Aerosols are tiny airbourne particles that come from forest fires, deserts, breaking ocean waves, pollution etc and leads to scattering and reflection of solar radiation - cooling affect
How does changes on the surface of earth affect global processes in terms of internal forcing
Albedo is critical in controlling the global energy budget, and human modification like black asphalt roads and roofs results in less radiation being reflected back off the earth.
How do we construct a climate record from the past
We use proxy data
What are climate proxys
They are preserved physical characteristics of the past that allow us to reconstruct the climatic conditions that occurred before modern observations began
Examples of proxies
Tree rings, ice cores, pollen, boreholes, corals, lake/ocean sediments
What has proxy data shown us about climate change over the last 2000 years
Shows temperature reconstructions based on all available proxy data.
Variability over this temporal scale is controlled by both external and internal processes
Difference between climate variability and climate change
Climate variability refers to variations in the mean state of the climate on all spatial/temporal scales beyond that of individual weather events
Climate change refers to a change in the state of the climate that can be identified by changes in the mean and the variability of its properties, and that persists for an extended period, typically decades or longer.
Climate change indicators
Atmospheric/oceanic temperatures, glaciers, snow cover, sea ice, sea level, and atmospheric water vapor.
Largest contributor to radiative forcing (climate change)
Increase in Co2 concentrations, primarily from fossil fuel emissions and secondarily from net land use change emissions.
Ocean acidification
Ocean absorption of roughly 30% of the emitted anthropogenic carbon dioxide
Greenhouse effect
The absorption of longwave radiation by the atmosphere, and re-emission in all directions results in a warming of the earths surface and lower atmosphere.
How is radiation transmission varied in the atmosphere
Atmosphere has regions where longwave radiation is more likely to be absorbed (greenhouse gases).
Atmosphere also has regions that are fairly transparent, especially to short wavelengths
Enhanced greenhouse effect
When extra ammounts of greenhouse gases are added from anthropogenic activities, they absorb more thermal radiation leading to extra warming
Walker circulation
The starting point of ENSO that is driven by differences in ocean surface temperature between east and west tropical south pacific
What controls the variability in air temperature and precipitation on large scales
El Nino-Southern Oscillation (ENSO)
Southern Oscillation Index (SOI)
Characterizes the intensity of the walker circulation.
When index is high (positive) the walker cell is normal and is called La Nina
When index is low (negative) the walker cell weakens and is called El Nino
Anthropogenic activities are said to have increased global warming by how much
1.0 degrees
Dynamic models used to simulate earths atmospheric and oceanic circulation realistically
General circulation models (GCM)
How do GCMs model climatology
Models are initiated with known climatology which then simulate atmospheric and oceanic processes over space and time using mathematics and physical laws.
Global surface temperature change expected at the end of the 21st century
1.5 degress relative to 1850-1900
The mean global temperature change from 1850-1900 to the end of the 21st century could be as large as _____ with a maximum temperature increase of ____
4.3 degrees, 5.4 degrees
How is precipitation in high latitude and sub tropical land areas expected to change by the end of the 21st century
Precipitation increase in high latitudes and precipitation decrease in most subtropical land regions
Mechanisms responsible for possible changes in precipitation on a global scale
- More intense Hadley circulation - higher precipitation in equatorial regions
- Decrease in subtropical regions - as the earth warms the extension of subtropical high pressure systems to higher latitudes will lead to further decreases
- Higher temperatures in the high latitudes will promote more moisture (clausius-claperyron relationship) in the atmosphere leading to more precipitation (more snow on ice sheets).
How much will sea level rise by 2100 relative to 1986-2005
Between 0.43 and 0.84m
Dominant form of sea level rise contribution
Glacier and ice sheet contributions, now more than the contribution from thermal expansion of the oceans
Glaciers and ice cap sea level rise capacity
41cm
Greenland and Antarctica ice sheet sea level rise capacity
7 and 58 metres
Precipitation likely to increase and decrease where in NZ
Increase in West and South, likely to decrease in North and East
Wind speed likely to _______ in the future in NZ
Increase, especially in winter
Warming is likely to increase greatly where in NZ
Up North and at high altitiudes
As a result of warming, how does ice volume and glacier decline affect NZ
Increased westerly airflow, higher precipitation and sea level rise by 40-100 cm by 2100
How does global warming increase westerly airflow
Evaporation intensifies as temperatures rise resulting in storms picking up more water vapor and heat making stronger winds and heavier rainfall
