Drivers of climate change Flashcards
What are the natural drivers of climate change which act over 10-100 years?
Inherent (random) atmospheric variability
Inherent or forced changes
Variability in volcanic aerosols
Solar variability?
What natural drivers of climate change act over 1000-100,000 years
Earth-orbital change result from variations in Earth’s orbit around the sun. These orbital changes alter the amount of solar radiation received on Earth by season and by latitude (10^3-10^5 years)
What natural drivers of climate change act over 1000,000 years?
Tectonic processes generated by Earth’s internal heat affect its surface by processes that alter the basic geography of the Earth’s surface
Changes in the strength of the sun
What is insolation?
Insolation is the amount of solar radiation (sunlight) received by Earth
What two factors determine the total amount of insolation Earth receives?
The strength of the sun and Earth-sun distance
Over what timescale do the sun’s strength and Earth-sun distance change?
Over millions of years
What controls the distribution of insolation over time?
Changes in Earth’s orbit
What are the three main types of orbital changes in the Milankovitch cycles?
Eccentricity, Obliquity (tilt), and Precession
What is eccentricity?
The shape of the Earth’s orbit, varying between more circular and more elliptical
What is obliquity?
The tilt of Earth’s axis, which affects the strength of the seasons
What is precession?
The wobble in Earth’s rotation axis, changing the timing of the seasons
Name the components of the climate system that respond to insolation changes?
atmosphere, biosphere, cryosphere, hydrosphere, lithosphere
Do different components of the climate system respond at the same speed?
No, they respond at different timescales
e.g. atmosphere = fast
Ice sheets= slow
What causes changes in the distribution of insolation?
Changes in Earth’s orbital geometry (eccentricity, precession and obliquity) cause changes in the distribution of insolation as a function of latitude
What is the current obliquity of Earth?
23.5 degrees
What are the obliquity values over 41,000 years?
Current value: 23.5 degrees
Range: 22.1 degrees to 24.5 degrees
What is the eccentricity values over the last 400,000 years?
Current value- 0.017
Range- 0-0.06
What makes eccentricity vary?
The gravitational pull of the other planets
The pull of another planet is strongest when the planets are close together
The net result of all the mutual interactions between planets is to vary the eccentricities of their orbits
What does eccentricity change?
It changes the total insolation received by the Earth but it differs by a maximum of 0.15%
What do tropical and subtropical regions have?
They have net excess of incoming solar radiation over outgoing back radiation
Where is excess tropical heat stored?
In a thin layer of the tropical ocean
What drives Earth’s general atmospheric and ocean circulation?
Heating imbalance
What does variations in insolation produce?
Variations in insolation produced large changes in the heating of tropical landmasses and in the strength of the summer monsoon at the 23,000 year precession cycle
Monsoon effect strongest in the Northern hemisphere, where the largest landmasses are
Where is an example of where monsoons effect most?
Africa
Summer: inflow of moist monsoonal air towards low pressure centre
Winter: dry continental outflow from high pressure centre over land
