Weather and climate Flashcards
What is palaeoclimatology?
The study of the climate prior instrumental measurements
Methods of palaeoclimatology
- Archives
- Chronology
- Proxies
- climate modelling
Uniformitariarnism
The same natural laws and processes that operate on Earth as they have in the past
Observed changes since 1950AD
- Earth, ocean and atmosphere has warmed
- Snow diminishing
- Earth, ocean and atmosphere has been
increasing 0.5 degrees Celsius since 1850 - 90% of accumulated energy since 1971-2010
is stored in oceans - Temperature is influenced by surface
temperature - People are measuring sea levels as
temperatures are causing oceans to expand
Observed changes in the Cryosphere
- sea ice is reducing
- Greenland and Antarctica ice sheets are
reducing in mass - Glaciers worldwide is reducing
- Antarctic sea ice and Northern Hemisphere Spring snow fall is decreasing
Observations in sea level rise
- The rate of sea level since 1850 was the
largest than anytime in the previous 2,000
years - From 1901-2010, sea level rose by 0.19m
- Sea levels were 5.5-9m higher than current
levels in the last interglacial period, Eemian
Atmospheric Greenhouse Gas
- CO2 concentrations have increased 40%
since pre-industrial times - CO2, CH4 and N2O have increased to levels
that has not been experienced in 800,000
years - CO2 = most abundant man made
greenhouse gasp that is increasing every
year
Observations in Ocean pH
- Declining and so more acidic - influenced by
CO2 dissolving in the ocean - About a 0.1 unit decrease
- 26% increase in H+
Climate change
- It’s happening more rapidly than any other event in the past ~55Myr
- Palaeoclimatology focuses on the climate
change in the cenozoic - Climate is long term
Controls on weather and climate
- plate tectonics = internal heating alters the
surface geography - Orbital changes = the earths path around the
sun influences the level of radiation the earth
receives - main source of energy to earth = sun
- where you are on earth affects the level of
radiation you receive - equator = more =
lower level of incident - earth tilt is important
Global energy balance
- Solar irradiative input is short wave radiation
- Earth’s output is long wave radiation
Global energy balance - processes
- Reflection = no temperature change
- Absorption = radiative energy is converted to
heat - Scattering = diffuse energy and lowers the
intensity caused by small particles in the
atmosphere
These influences the earths temperature
Reflection
No temperature change
Climate drivers
Natural and anthropogenic substances and processes that alters the earth energy balance
Radioactive forcing
The changes in energy fluxes caused by changes in climate drivers
Albedo
- the reflective quality of a surface and is expressed by %
- 0% = observed
- the composition of a surface
influences albedo - The angle of the sun impacts
reflection. Lower angle has
lower energy and creates
greater reflection - Tropics = 23.5 N 23.5 S = lower
reflection = 19-38%
Surface heat flux
Urban heat island - 60% = roofs and pavements
Built up areas are far warmer
Surface heat flux - consequences
- Impaired air quality
- Illnesses
- Increased energy use
Surface heat flux solutions
- Brighter coloured surfaces
- Vegetation on roof tops
GHGs
- Increase concentration has
been the recent biggest
contributor to positive radiative
forcing - Paris agreement has brought it
down to 1.5 degrees Celsius
Insolation
- Incident solar radiation = radiant energy received from the sun at the top of the Earth’s atmosphere
- Average = solar constant
Insolation - short term
- Sunspots
- Regional temperatures very low
Insolation - long term
Milankovitch Cycle
- Precession (wobble) - ~19,000 to 23,000 yr cycle
- Obliquity (tilt) - ~41,000 yr cycle
Tilt varies between 21.5 - 24.5 degrees. Currently 23.5 - Eccentricity (elliptical orbit) - ~100,00 to 420,000 yr cycle
Ocean circulation
Heat transport system
Zachos curve
Temperature inferred from benthic foraminifera 18O
