Climate Notes
Evidence for climate change
Where does the temperature
data come from?
- Modern data: weather
stations - data to late 1800’s
- Increasing urbanization
will cause increase in temperature independent of global temperature changes
- Correct for
problem by comparing stations with nearest rural stations
- Modern data: sea surface temperatures
- Use remote sensing (satellites)
to measure temperatures of ocean surface
- Data goes back two decades
- Seasonal/cyclical variations
(El Ninos/La Ninas)
- Expressed as difference from
time average (anomalies - positive is warmer than average)
- Ancient data: oxygen isotopes
- Oxygen naturally occurs in
two isotopes (atoms with different numbers of neutrons, hence masses)
- O-16 and O-18
- Different proportions of O-16
and O-18 are dissolved in water at different temperatures
Ratios of O-16/O-18 in ice or rock is an indicator of temperature
- Found in Antarctic ice cores
- back to about half million years
- Found in rock - back millions
of years
Where does the CO2 data come from?
- Modern data - Mauna Kea observatory
- Ancient data - ice core air bubbles
- Really ancient data - inference
from oceanic pH
Geologic impacts of climate
change
- Alaska: Two different climate
models predict increase in both temperature and precipitation
- Impact: Thawing permafrost
- “thermokarst”
damage - pits, humps, leading to increased erosion and river silting
- Agricultural and fisheries
impact
- Melting sea ice
- Rising sea level, increased
storm surges and coastal erosion, disrupted marine ecosystems
- Gulf Coast: Different models give
different predictions - either a moderate increase or dramatic increase in
temperature, and either a small decrease to large increase in soil moisture
- Impact on water supply difficult
to predict - if falling moisture, might be overdrafts of ground water
- Rising sea level means
- loss of coastal land
- loss of storm surge buffer
- potential slat water intrusion
into wells
- California:
- Changes in rainfall/snowmelt
- Less snow, more rain means
runoff all winter instead of water stored in mountains
- More rainfall ends up
in ocean, less stored behind dams
- Water supply issues
- Rising sea level
- Threatens Sacramento-San
Joaquin delta
- Sinking Delta islands mean
levees are already wet too often
- Rising sea level means higher
tidal flow back up the Delta channels
- Water supply issues