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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
Greenland
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.
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.
http://visibleearth.nasa.gov/view.php?
id=76590
http://earthobservatory.nasa.gov/I
OTD/view.php?id=79369&src=ve
From: Kitchen (2014) – Global Climate Change
Arctic Sea Ice
http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_
ice.php
National Snow and Ice Data Center
(NSIDC)
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.
“The nine lowest maximum extents have occurred in the last nine
years, since 2004,” Meier says.
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
Shorter
wavelengths
and higher
energy
Wavelengths
(not to scale)
Gamma
rays
X rays
0.001 0.01 0.1 1
Nanometers
UV
radiation
10 0.1
Infrared
radiation
10
Micrometers
Microwaves TV, Radio waves
100 0.1 1
10 1
10 100
Centimeters
Meters
Longer
wavelengths
and lower
energy
Electromagnetic Spectrum: light = energy = waves
Flow of Energy to and from the Earth
Solar
radiation
Radiated by
atmosphere
as heat
Reflected by
atmosphere
UV radiation
Most UV absorbed
by ozone
Lower Stratosphere (ozone
layer)
Visible
light
Troposphere
Heat added to
troposphere
Heat radiated
by the earth
Greenhouse effect
Absorbed
by 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
Carbon dioxide in
atmosphere
Carbon
Cycle
Respiration
Photosynthesis
Animals
(consumers)
Diffusion
Burning
fossil fuels
Forest fires
Plants
(producers)
Deforestation
Transportation
Respiration
Carbon in
plants
(producers)
Carbon dioxide
dissolved in ocean
Carbon in
animals
(consumers)
Decomposition
Marine food webs
Producers, consumers,
decomposers
Carbon in limestone
or dolomite
sediments
Carbon in
fossil fuels
Compaction
Process
Reservoir
Pathway affected by humans
Natural pathway
Fig. 3-19, p. 70
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