climate, weather, and storms. weather and climate weather is day-to-day variability of temperature,...
TRANSCRIPT
Climate, weather, and storms
Weather and climate
• Weather is day-to-day variability of temperature, pressure, rainfall, wind humidity, etc.
• Climate is the long-term average of weather for a particular region (local, regional, or global)
Incoming solar radiation
Approximately 50% of the solar energy that strikes the atmosphere reaches Earth’s surface
30% is reflected back to space
20% is absorbed by clouds and the atmosphere’s gases
Most outgoing Earth radiation is intercepted and absorbed by greenhouse gases like water vapor, methane, and carbon dioxide.
What are the greenhouse gases?
(excluding H2O)• Carbon Dioxide: 49%
• Methane: 18%
• “CFC’s from coolants, solvents, etc”: 14%
• Nitrous Oxides: 6%
• Others: 13%
The greenhouse effect
Some atmospheric basics
• The greenhouse effect • Radiant energy that is absorbed heats Earth
and eventually is reradiated skyward– Radiation is in the form of longwave infrared
radiation
– Atmospheric gases, primarily H2O and CO2, are more efficient absorbers of longwave radiation
– This selective absorption, called the greenhouse effect, results in warming of the atmosphere
• Climate is fundamentally driven by energy from the Sun.
• Changes in the energy budget at Earth’s surface are primarily affected by changes in the solar energy received by Earth– Secondary effects: differences in albedo, and
atmosphere composition
Latitudinal variation in solar input
Multi-year time scale variations
• El Nino and La Nina are important phenomena
• Occur every ~2 to 7 years when typical ocean-atmosphere circulation breaks down
During normal years, warm surface waters in the Pacific lie in the east
off Indonesia
When the pattern oscillates to an “El Nino”, the warm water shifts east
“La Nina” is characterized by colder sea-surface temperatures and
stronger trade winds in the eastern tropical Pacific
SouthAmerica
During “Normal Years”During “Normal Years”
Warm water in the western Pacific causes low pressure and high rainfall;pressure system drives tradewinds from east to west;tradewinds drive warm water to the west;causing cold water to rise off South America and flow west.
SouthAmerica
During “El Nino”During “El Nino”
Warm water shift to the eastern Pacific causes drought in western Pacific;low pressure over the warm eastern Pacific causes heavy rainsand inhibits upwellings along the coast of South America.
SouthAmerica
During “El Nino”During “El Nino”
Warm water shift to the eastern Pacific causes drought in western Pacific;low pressure over the warm eastern Pacific causes heavy rainsand inhibits upwellings along the coast of South America.
Strong El Nino year 1982-83:
1982-83 El Nino
• Floods in Peru-Ecuador (600 fatalities)
• California flooding led to $300 million damages
• Hurricanes in Hawaii, Tahiti
• Australia: drought and wildfires
1997-1998 El Nino Effects
La Nina hazards
• Can bring warming and low rainfall to much of U.S.– Can lead to fires
• Allows growth of hurricanes in Atlantic
19582003
Climate Change
Records of Climate ChangeRecords of Climate Change
National Academy of Science Report, 2006
Records of Climate Change
• Historical data
• Proxy data– Marine sediment– Ice – Coral – Lake sediment– Tree Rings– Boreholes– Glacial advance/retreat– Old glacial deposits, etc.
Oxygen isotopes
• Same atomic number (8)
• Different atomic mass
99.63% 0.0375% 0.1995%concise.britannica.com
Delta notation
Ice data
• Influence of temperature on ice composition
• Record of atmospheric composition
earthobservatory.nasa.govComposition of precipitation versus temperature
Greenland and Antarctic Ice Sheet Records
>700,000 yrs Layers counted
like tree rings
Greenland and Antarctic Ice Sheet Records
>700,000 yrs Layers counted
like tree rings
Photos: NASA
Figure 21.5A
Interpreted from Greenland ice core O-isotope data
Seafloor record
• Microfossils of organisms in surface and bottom water
• Limited by age of oceanic crust (oldest ~180 my)
Source: NOAA
Influence of ice volume on O-isotope composition of
seawater
• Ice is depleted in 18O
• Residual seawater is enriched in 18O
• Positive (18O-enriched) values of organisms indicate larger ice volume
Influence of ice volume on O-isotope composition of
seawater
Figure 21.4
Temperature effects
The ratio of 18O to 16O in foraminifera shells varies slightly depending on the temperature of the surrounding water, as well the water's salinity.
Dealing with temperature effect
• Use benthic organisms in from deep bottom waters (relatively constant temperature)
• Use trace element ratios tied to precipitation temperature (e.g., Sr/Ca)
Figure 21.8
Annual growth rings in x-rayed coral (NASA)
Chapter 21 Opening Figure
Figure 21.6
Ring thickness and density a function of climate (e.g., high latitude and altitude trees sensitive mainly to temperature)
Cross dating in dendrochronology
Mapping glacial deposits
Figure 18.32300 my old glacial deposits on Pangaea
Long term climate recordLong term climate record
Climate Variations over Time
• Early earth: atmosphere full of CO2
• Surface would have been much hotter because of greenhouse effect
• What changed? Much CO2 has gone into rock form (limestones primarily)
Figure 21.5B
Interpreted from Greenland ice core O-isotope data
