NATS 101 Lecture 25 Climate Change (cont

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NATS 101 Lecture 25Climate Change (contd)
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Absorption
Visible

• 20 of incident Visible (0.4-0.7 ?m) is absorbed
• O2 an O3 absorb UV (shorter than 0.3 ?m)
• Infrared (5-20 ?m) is selectively absorbed
• H2O CO2 are strong absorbers and emitters of IR
• Little absorption of IR around 10 ?m
  atmospheric window

IR
Ahrens, Fig. 2.9
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The Natural Greenhouse Effect clear sky
CH4 N20 6
O3 8
Water Vapor 60
Carbon Dioxide 26
Clouds also have a greenhouse effect
Kiehl and Trenberth 1997
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CO2 makes the biggest contribution to the climate
forcing
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Global Warming Potential (GWP)

• Different gases has different warming potentials
  which are defined relative to the warming effect
  of CO2

Gas GWP Carbon dioxide (CO2) 1 Methane (CH4)
21 Nitrous oxide (N2O) 310 Hydrofluorocarbons
560-12,100 Perfluorocarbons 6,000-9,200 Sulfu
r hexafluoride 23,900
Ahrens, Fig 2.10
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Changing CO2 concentrations

• CO2 concentrations measured very precisely since
  1958
• Over past 45 years theyve increased by 21
• Present 0.6/yr
• increase

You are here
See http//www.cmdl.noaa.gov/ccgg/trends/co2_data_
mlo.php
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Changing atmospheric composition CO2

• Over past 45 years theyve increased by 21
• Present 0.6/yr increase

Data from Climate Monitoring and Diagnostics
Lab., NOAA. Data prior to 1974 from C. Keeling,
Scripps Inst. Oceanogr.
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Context 400,000 years of Antarctic ice core
records of Temperatures, Carbon dioxide and
Methane.
Last ice age glacial 20,000 years ago
Source Hansen, Climatic Change 2005, based on
Petit, Nature 1999
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Changing CO2 concentrations

• CO2 concentrations have varied naturally by
  30-50 over the past few hundred thousand years
  (ice ages)
• Fossil fuel burning since the industrial
  revolution has created a recent sharp increase in
  CO2 concentrations
• CO2 concentrations are now higher than at any
  time in past few hundred thousand years
• And concentrations are increasing faster with time

Last 4 Ice Age cycles 400,000 years
Man made
You are here
See http//epa.gov/climatechange/science/recentac.
html
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CO2 Temp.
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Increasing CO2 concentrations

• How high will they go? How warm will it
  get???
• If CO2 concentrations stay within factor of 2 of
  pre-industrial, then warming of 31oC is expected
• If concentrations go still higher gt larger
  uncertainty because the climate is moving into
  unprecedented territory

See http//epa.gov/climatechange/science/futureac.
html
You are going to be somewhere in here
Last 4 Ice Age cycles 400,000 years
Man made
You are here
Ice age CO2 range
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Predictions of increased CO2 Temperature
Emissions High Medium Low
Constant 2000 CO2
Multi-model global averages of surface warming
(relative to 1980-99) for the scenarios A2, A1B
and B1, as continuations of the 20th century
simulations. Shading is plus/minus one standard
deviation range of individual model annual
averages. Trenberth/IPCC
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Missing Carbon Sink
Woods Hole web page

• CO2 is accumulating in the atmosphere more slowly
  than expected (believe it or not)
• Based on our understanding of CO2 emissions and
  ocean and atmosphere uptake, there is a missing
  sink/uptake of about 25

NASA OCO mission
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Ocean Carbon Uptake
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Ocean Uptake of CO2

• SciAm article

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The Oceans Global Change

• Much of this material is courtesy of
• Julia Cole, here in Geosciences at UA
• and
• Kevin Trenberth at the National Center for
  Atmospheric Research NCAR

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(No Transcript)
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Ocean Transport of Heat
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3D Conveyor Belt Concept
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Potential Changes Related to the Ocean
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Change in Thermohaline Circulation
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Change in Ocean Chemistry
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Ocean Acidification (SciAm article)

• Currently 1/3 of CO2 released by burning fossil
  fuels ends up in the ocean.
• Absorbed CO2 forms carbonic acid in seawater,
  lowering the slightly alkaline pH level, changing
  the balance of carbonate bicarbonate ions.
• Shift toward acidity ensuing changes in ocean
  chemistry, make it more difficult for creatures
  to build hard parts out of calcium carbonate.
• Decline in pH thus threatens a variety of
  organisms, including corals, which provide one of
  the richest habitats on earth.
• Within a century, Southern Ocean surface will be
  corrosive to shells of tiny snails key in the
  marine food chain within this highly productive
  zone.

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Sea level is rising
from ocean expansion and melting glaciers

• Since 1993
• Global sea level
• has risen 43 mm
• (1.7 inches)
• 60 from
• expansion as ocean temperatures rise,
• 40 from melting glaciers

from Steve Nerem via Trenberth
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Observed Ocean Warming

• Most oceans are warming
• Figures from Hansen et al 2006

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Evidence for reality of climate change
Glaciers melting
Muir Glacier, Alaska
1909 Toboggan Glacier Alaska 2000
1900 2003 Alpine glacier, Austria
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Research indicates that less than 8F of Arctic
warming caused Greenland to lose enough water to
raise sea level by up to 12 feet during the Last
Interglacial Period
Today
125,000 years ago
Image from Bette Otto-Bliesner, National Center
for Atmospheric Research
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BUT, sea level rise during the Last Interglacial
Period appears to have been more it was likely
up to 21 feet. A reduced Greenland Ice Sheet
could only have contributed up to 12 feet Where
did the rest of the water come from?
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Today
Most likely Antarctica
East Antarctic Ice Sheet
West Antarctic Ice Sheet
http//svs.gsfc.nasa.gov
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125,000 years ago - the West Antarctic Ice Sheet
may have been gone
East Antarctic Ice Sheet
Late Quaternary diatoms and anomalously high 10Be
found in sediments under the ice sheet
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1 meter
2 meters
www.gfdl.noaa.gov
4 meters
8 meters
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Surface melt on Greenland


Increasing melt zones. Melt descending into a
moulin a vertical shaft carrying water to the
base of the ice sheet. NSIDC (above) Braithwaite
Univ. Manchester
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Greenland ice mass budget
A great deal of effort is going into estimating
how the Greenland ice sheet is changing
Researchers Mass Change Method
Time Span
(GT/year) Krabill et al. 2000 -47
Aircraft Surveys 1994-1999 Velicogna et al.
2006 -200 to -260 GRACE
2002-2006 Luthcke et al. 2007 -145 to -175
GRACE 2003-2006 Zwally et al. 2007
-80 to -100 ICESat 2003-2005 GRACE
is a gravity recovery mission ICESat is a lidar
topographymission NASA website on Greenland ice
sheet
100 GT/yr 0.3 mm/yr sea level rise
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Snow cover and Arctic sea ice are decreasing
Arctic sea ice area decreased by 2.7 per
decade (Summer -7.4/decade) 2007 22 (106
km2) lower than 2005
Spring snow cover shows 5 stepwise drop during
1980s
Trenberth/IPCC
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Arctic sea ice disappears in summer by
2050 Already 2007 lowest on record by 22
Abrupt Transitions in Summer Sea Ice

• Gradual forcing results in abrupt Sept ice
  decrease
• Extent decreases from 80 to 20 coverage in 10
  years.
• Relevant factors
• Ice thinning
• Arctic heat transport
• Albedo feedback

2007 x
Trenberth from Holland et al., GRL, 2006
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Land surface temperatures are rising faster than
SSTs
SST Land
Annual anomalies of global average SST and land
surface air temperature Land increased 0.4oC vs
ocean suggesting 3 decrease in RH over land
Trenberth/IPCC
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Controlling Heat
Human body sweats Homes Evaporative coolers
(swamp coolers) Planet Earth Evaporation (if
moisture available)
e.g., When sun comes out after showers, the
first thing that happens is that the puddles dry
up before temperature increases.
Trenberth
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Water vapor increase at higher temperatures
Water holding capacity of atmosphere increases
about 7 per oC (4 per ?F) increase in
temperature.
Observations show that water vapor in LOWER
troposphere is indeed increasing. Surface
temperature increase 0.6?C since 1970 over
global OCEANS and 4 more water vapor.
Total water vapor
Since late 1970s, ocean surface has been warming
at 0.14?C/decade gt 1 WV increase/decade.
Observed WV trend since 1988 is 1.2 per decade
From Trenberth/IPCC
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Land precipitation is changing significantly over
broad areas
Smoothed annual anomalies for precipitation ()
over land from 1900 to 2005 other regions are
dominated by variability.
Trenberth/IPCC
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Proportion of heavy rainfalls increasing in most
land areas
Regions of disproportionate changes in heavy
(95th) and very heavy (99th) precipitation
Trenberth/IPCC
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Declining Snow Pack in many mountain and
continental areas contributes to drought

• more precipitation falls as rain rather than
  snow, especially in the fall and spring.
• snow melt occurs faster and sooner in the spring
• snow pack is therefore less
• soil moisture is less as summer arrives

• the risk of drought increases substantially in
  summer
• Along with wild fire

Trenberth
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Drought is increasing most places
Mainly decrease in rain over land in tropics and
subtropics, but enhanced by increased atmospheric
demand with warming
The most important spatial pattern (top) of the
monthly Palmer Drought Severity Index (PDSI) for
1900 to 2002. The time series (below) accounts
for most of the trend in PDSI.
Trenberth/IPCC
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Rising greenhouse gases are causing climate
change, and arid areas are becoming drier while
wet areas are becoming wetter. Water
management- dealing with how to save in times
of excess for times of drought will be a major
challenge in the future.
Lake Powell
Trenberth
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Heat waves and wild fires
Impacts on human health and mortality, economic
impacts, ecosystem and wildlife impacts
Trenberth
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Extremes of temperature are changing! Observed
trends (days) per decade for 1951 to 2003 5th
or 95th percentiles From Alexander et al. (2006)
Trenberth/IPCC
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Global Atmo Energy Imbalance
Increasing GHG concentrations decrease Energy
out So Energy IN gt Energy OUT and the Earth warms
Ahrens, Fig. 2.14
IR Out is reduced
Solar in
Atmosphere
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Heat waves are increasing an example
Extreme Heat Wave Summer 2003 Europe 30,000 deaths
Trenberth/IPCC
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Trenberth
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CO2 emissions in different regions in 2000 in
terms of emissions per capita (height of each
block) population (width of each block) and
total emissions (product of population and
emissions per capita area of block). Source
M. Grubb, http//www.eia.doe.gov/iea/
Trenberth
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Trenberth