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Global Climate Change
• Earth is Warming• How do we know?• What do we know?
• How confident are hypotheses about causes?• What are greenhouse gases?• Where do they come from, and how do we know?
• Most common claims of the skeptics• T’s are going down, not up• This warming is just part of a natural cycle• CO2 is good for plants
Global Climate Change
• Earth is Warming• How do we know?• What do we know?
• How confident are hypotheses about causes?• What are greenhouse gases?• Where do they come from, and how do we know?
• Most common claims of the skeptics• T’s are going down, not up• This warming is just part of a natural cycle• CO2 is good for plants
NOAA Global Historical Climatology Network: DATA
Stations with at least 10 years of record for these 30-yr intervals
http://www.ncdc.noaa.gov/oa/climate/ghcn-daily/
The Historical T Data Network
From: Kitchen (2014) – Global Climate Change
Anomalies instead of Absolute T Data
1. Variations from station to station can be erratic due to small variations in local conditions
2. Regional anomalies are much more consistent, over a larger area, than station to station readings.
3. Anomalies allow more accurate assessment of T variation through time.
Days vs. Nights
From: Kitchen (2014) – Global Climate Change
Days vs. Nights
From: Kitchen (2014) – Global Climate Change
IPCC - Data
IPCC - 2007
IPCC – Last 2000 yrs
IPCC- 2007
Land + Ocean T’s
National Research Council (2010) – weather stations + SST’s from direct and satellite measurements.
Melting Ice
http://visibleearth.nasa.gov/view.php?id=76590
Jakobshavn is the fastest-flowing glacier in the world. In 2010, the glacier moved at 15 kilometers per year, shedding ice into the Arctic Ocean as it surged from land to sea. It drains more than six percent of the Greenland ice cap and contributes more to global sea level rise than any other feature in the Northern Hemisphere. The glacier has both retreated and thinned in recent years. In 2010, Jakobshavnretreated 1.5 kilometers.
Greenland
http://earthobservatory.nasa.gov/IOTD/view.php?id=79369&src=ve
Antarctica
Two weeks after a new record was set in the Arctic Ocean for the least amount of sea ice coverage in the satellite record, the ice surrounding Antarctica reached its annual winter maximum—and set a record for a new high. Sea ice extended over 19.44 million square kilometers (7.51 million square miles) in 2012, according to the National Snow and Ice Data Center (NSIDC). The previous record of 19.39 million kilometers (7.49 million square miles) was set in 2006.
From: Kitchen (2014) – Global Climate Change
Arctic Sea Ice
Over the last decade, Arctic sea ice extents in September have set record lows three times, and the 2011 minimum nearly tied the 2007 record low.
National Snow and Ice Data Center (NSIDC)
“The nine lowest maximum extents have occurred in the last nine years, since 2004,” Meier says.
http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice.php
Warming + Melting = Sea Level Rise
From: Kitchen (2014) – Global Climate Change
Global Climate Change
• Earth is Warming• How do we know?• What do we know?
• How confident are hypotheses about causes?• What are greenhouse gases?• Where do they come from, and how do we know?
• Most common claims of the skeptics• T’s are going down, not up• This warming is just part of a natural cycle• CO2 is good for plants
Causes of Warming – How confident?
Visible light
Gamma rays
X raysShorter wavelengths and higher energy
Longer wavelengths and lower energy
UV radiation
Infrared radiation Microwaves TV, Radio waves
Wavelengths (not to scale)
0.001 0.01 0.1 1 10 0.1 10 100 0.1 1 10 1 10 100
Nanometers Micrometers Centimeters Meters
Electromagnetic Spectrum: light = energy = waves
Solar radiation
Reflected by atmosphere
Radiated by atmosphere as heatUV radiation
Lower Stratosphere (ozone layer)Most UV absorbed
by ozone Visible light Heat added to
troposphereTroposphere
Heat radiated by the earth
Greenhouse effect
Absorbed by the earth
Flow of Energy to and from the Earth
From: Miller (2010) Living in the Environment
What’s a Greenhouse Gas?
• Greenhouse gases respond to long-wave radiation (infrared radiation) by ‘vibrating’ – this vibration sends out (or re-radiates) a portion of that original infrared radiation – heat.
• Some of these are:• Water vapor• Carbon dioxide• Methane• CFCs• Ozone
Yellow = observed by satellites
Valleys = absorption by GHG’s
CO2 could raise overall heat budget of atmos. by 3%
National Research Council - GHG
Analysis of air bubbles trapped in Antarctic ice cores show that, along with carbon dioxide, atmospheric concentrations of methane (CH4) and nitrous oxide (N2O) were relatively constant until they started to rise in the Industrial era. Atmospheric concentration units indicate the number of molecules of the greenhouse gas per million molecules of air for carbon dioxide and nitrous oxide, and per billion molecules of air for methane. Source: U.S. Global Climate Research Prog.
How Do We Know We’re Adding CO2 to the
Atmosphere? 14C!• Living things incorporate 14C into their bodies in the
same proportion as it occurs in the atmosphere
• When the organism dies, it begins to lose 14C, via radioactive decay [half-life of 5730 yrs]
• Tree rings record relative amounts of 14C in the atmosphere, and show a large increase in the proportion of 12C since the industrial revolution
• This comes from fossil fuels, which are too old to have any 14C remaining
Fig. 3-19, p. 70
Carbon dioxide in atmosphere Respiration
Photosynthesis
Animals (consumers) Burning
fossil fuelsDiffusion Forest fires
Plants (producers)Deforestation
Transportation RespirationCarbon in
plants (producers)
Carbon dioxide dissolved in ocean
Carbon in animals
(consumers)Decomposition
Marine food webs Producers, consumers, decomposers
Carbon in fossil fuels
Carbon in limestone or dolomite sediments
Compaction
Process
Reservoir
Pathway affected by humans
Natural pathway
Carbon Cycle
Trends in CO2 : NOAA
http://www.esrl.noaa.gov/gmd/ccgg/trends/history.html
Temperature and CO2
Temperature change (blue) and carbon dioxide change (red) observed in ice core records Many other records are available
Temperature and CO2
An estimate from the tropical ocean, far from the influence of ice sheets, indicates that the tropical ocean may warm 5°C for a doubling of carbon dioxide. The paleo data provide a valuable independent check on the sensitivity of climate models, and the 5°C value is consistent with many of the current coupled climate models.
Temperature Projections - NOAA
http://www.climate.gov/#education/teachingResources
Global Climate Change
• Earth is Warming• How do we know?• What do we know?
• How confident are hypotheses about causes?• What are greenhouse gases?• Where do they come from, and how do we know?
• Most common claims of the skeptics• T’s are going down, not up• This warming is just part of a natural cycle• CO2 is good for plants