Download Atmosphere, the Water Cycle and Climate Change

Atmosphere, the Water Cycle
and Climate Change
OCN 623 – Chemical Oceanography
Outline
1. The water cycle
2. Climate and climate-change
• Atmosphere radiation balance
• CO2 and other greenhouse gases
• Aerosol effects
• Cloud effects
3. Climate change implications
• Sea-level rise
• Sea ice loss
• Storm intensification
4. Climate change mitigation
The Water Cycle
“The annual circulation of H2O
is the largest movement of a
chemical substance at the
surface of the Earth”
The distribution of water at the
Earth's surface:
% of total
Oceans
97.25
Ice caps and glaciers
2.05
Groundwater
0.68
Lakes
0.01
Soils
0.005
Atmosphere (as vapor)
0.001
Rivers
0.0001
Biosphere
0.00004
70% of the sun’s energy is absorbed at the Earth’s
surface, where it drives the hydrologic cycle
Solar Energy Budget
Three-cell Model of Atmospheric Circulation
(1) Polar cells
(2) Midlatitude
cells
(3) Hadley cells
Idealized vs. actual zonal (E-W) pressure belts
Non-uniform surface = uneven heating
Unstable windflow = eddies
Sun doesn’t remain over the equator year-round = 23.5N-23.5S
Movement of H2O through the
atmosphere determines the distribution
of rainfall
Global average precip ≈ 943mm/yr
Net evaporation from the surface ocean
• affects surface water salinity in the ocean
• increases surface water density
• controls thermohaline circulation of ocean
Surface water salinity
in the Atlantic Ocean
The maxima in
evaporation-precipitation
results in the highest
surface water salinities
in the mid-latitudes
around 30 N and 30S
What does “Climate” mean?
Webster:
“Climate: the average condition of the weather at a
place over a period of years as exhibited by
temperature, wind velocity, and precipitation”
So “climate” refers not to the weather today or this week or this
year, but rather to the range of weather (including hot and cold
years, wet and dry years) that is typical of each region.
10
Is Climate Change / Global Warming
Happening or Not?
Global mean surface temperature has increased >0.5˚C in this time.
Is this natural variability or anthropogenic climate change??
How does climate change work?
The Earth’s temperature is set by a Radiation Balance:
If more heat arrives from the sun than can escape as
infrared (IR) rays, the Earth gets warmer.
The average Albedo
(reflectivity) of Earth is 0.3
The majority of outgoing IR
comes from gases
13
From the Terra satellite, you can actually see the regions where
IR radiation escapes (left) and solar radiation is absorbed (right)
Greenhouse gases trap IR, causing a warming effect.
Source: TERRA Mission; CERES Instrument; NASA
Mauna Loa Monthly Carbon Dioxide Record
Keeling Record 1958 - 2008
ppmv
CO2 is the most important
greenhouse gas (one that
prevents the escape of IR that
would normally cool the Earth)
1900 – 293
ppmv 1940
– 307
ppmv
Challenges
of a
Changing
Earth
—
July
2 upload.wikimedia.org
001
Ocean CO2 Increase Tracks Atmosphere
“Ocean Acidification”
Preindustrial
(1700s)
pH
Global Carbon Cycle
Reservoirs in GtC and fluxes in GtC/yr
Most carbon has been stored in the ocean*. It plays a huge role in
controlling greenhouse gases and climate
*although most of the CO2 man has released is still in the atmosphere
CO2 Emissions and Uptake Since 1800 (Gt C)
CO2 Emissions
140
Deforestation Land use
change
Coal
Oil
265
?
115
Oceans
110
Natural
Fossil
gas emissions
Cement
making
Where the CO2 goes
?
Dissolution
into the ocean
Reforestation
Terrestrial
180
Atmosphere
Our fuel burning is converting fossilized carbon
(coal, oil, and natural gas) into CO2, and 45% of it stays in the air
We can look at ice cores to see that CO2 was pretty constant
for the last thousand years.
The rapid increase began about the time of the industrial revolution
Global Temperatures Are Linked to
Atmospheric CO2
Vostok Ice Core CO2 Concentration and Temperature Variation Record
325
4
300
2
275
0
250
-2
225
-4
200
-6
175
-8
150
-10
Floor at ~190 ppm
400,000
300,000
200,000
100,000
Years Before Present
Source: Barnola, et.al.; Petit et.al. (PAGES / IGBP)
Challenges
of
a
Changing
Earth
—
July
2001
0
Temperature
CO2 concentration (ppmv)
Ceiling at ~290 ppm
CO2 Concentration CO
inConcentration
Ice Cores
and Atmospheric CO2
in Ice Core Samples and
for Next 100 Years
Projected
Projection for Next 100Projections
Years
(2100)(2100)
Projected
2
700
The Earth is now in a NO-ANALOG zone!
600
VostokEarth
Record has never before dealt with these conditions.
The inhabited
550
IPCC IS92a Scenario
Law Dome Record
Mauna Loa Record
Therefore, paleo records cannot be 100% reliable tests of climate
models.
500
450
400
Current
(2001)
Current
(2001)
350
300
250
200
150
400,000
300,000
200,000
100,000
0
Years Before Present
Source: C. D. Keeling and T. P. Whorf; Etheridge et.al.; Barnola et.al.; (PAGES / IGBP); IPCC
Challenges
of
a
Changing
Earth
—
July
2001
21
CO2 Concentration (ppmv)
650
Model predictions
from IPCC:
Models
Observations
Paleo Record
Source: IPCC Third Assessment Report, WG1
“Global
temperature
will rise from 1.45.8˚C over this
century unless
greenhouse gas
emissions are
greatly reduced.”
22
Aerosol Radiative Forcing of Climate
Climate Models didn’t do a very good job of reproducing
temperature trends in the last 150 years when they did
not include aerosol impacts.
Radiative Forcing
Direct
Indirect
Models do much better when they include aerosols,
even using crudely understood aerosol effects
Models with Aerosol Effects
Not every place is warming, though - the blue spots are
areas that have been cooling.
How could that be?
Each of these areas is polluted with aerosols.
Aerosol Forcings Cause the Largest Uncertainty in the
Earth’s Radiation Budget
Level of
Scientific
Understanding
27
Source: IPCC ThirdB.Huebert
Assessment Report
Dust can have a huge impact on climate, both by scattering
light to space and by absorbing light
Where this Saharan dust cloud is, there is more light reflected
back to space than over the dark ocean:
Smoke and Dust Both Affect Climate
Image courtesy of NASA and Orbimage
.
The whitest
things (most
reflective of
sunlight) in this
SeaWiFS image
are clouds
Changing the
extent or density
of clouds is called
the radiative
indirect effect on
climate
Image courtesy of NASA and Orbimage
MODIS Image
NW Pacific
29 April 2002
Indirect effect of
aerosols:
What are these
wiggly lines
among the
clouds?
Ship tracks in the Atlantic. These are strong evidence of the
Indirect Effect of aerosols on clouds: More aerosol nuclei make
clouds whiter (more reflective of sunlight)
31
SOLAS Summer School 2009
SOLAS Summer School 2009
Likely Impacts of Climate Change
Why should we worry about global warming?
Would an extra degree or two of warming hurt
anything?
What changes might we see?
Would an Extra Degree or Two of
Warming Hurt Anything?
YES!! It’s NOT just about warming:
“Climate Change” includes:
Sea-level rise
Droughts & flooding
Severe storms increasing
Spread of diseases to new areas
A warmer climate would
melt glaciers, expand the
ocean, and submerge
many Polynesian islands!
Temp Forecast
Temperature Rise
+1 to 3°C
⇓
Sea Level Rise
+10 to 90 cm (5 to 37”)
Sea Level Forecast
Recent Analyses Increase the
Sea Level Rise Forecast
Intergovernmental Panel on Climate Change
4th Assessment Report (FAR) Feb 2007
The last time the polar regions were significantly warmer
than present for an extended period (about 125,000
years ago), reductions in polar ice volume led to 4 to 6
metres of sea level rise.”
Arctic Sea-Ice Extent is Shrinking Rapidly
Change from 1980 to 2009
Arctic sea ice has lost half its thickness
1958-76
1993-97
www.grida.no/climate/vital/30.htm
Positive Feedback: Warming Causes More Warming!
1 Light colored ice reflects back the Sun’s energy
efficiently.
2 Exposed land is darker and absorbs more energy;
warming.
3 As the ice melts, more land is exposed. This
absorbs more heat, melting more ice, and causing
further warming.
4 The altitude of the melting ice is reduced so it
becomes harder for new ice to form (esp for
Greenland).
Melt water flows
to the base of the
Greenland ice
sheet.
Ice is melting MUCH
faster than
glaciologists had
forecast
Positive Feedback can cause
Runaway Warming,
by darkening originally-light
surfaces.
The climate system is
full of feedbacks
Hurricanes are Becoming More Intense
Webster et al., Science, 309, 1844-1846, 2005
The number of Category 4 and 5 hurricanes worldwide has nearly doubled over
the past 35 years, even though the total number of hurricanes has dropped since the 1990s.
The shift occurred as global sea surface temperatures have increased over the same period. This is
compelling evidence that global climate change is making tropical storms more
powerful and more damaging.
Climate change is expected to increase the range of
diseases like malaria
There are arguments against Climate Change
… which have been debunked by the (reputable) scientific
community
www.skepticalscience.com
… and dozens more are addressed at this URL
You can always find someone who is willing to be bought
and corporations with the money to do so
Some of the unexpected cold winter weather is due to a (natural) Arctic
Oscillation in weather patterns.
Such oscillations can obscure longer-term trends.
What are the Dominant Forcings?
Jim Hansen -- NASA Goddard Institute for Space Studies
Observed temperature change simulations for different forcings
Soot (black carbon) + O3 +CH4 yields ~ same warming as CO2
Inferences
1. Non-CO2 Forcings are Substantial
Comparable to CO2 forcing today
2. Strategic Mitigation Role
If coal is phased out, non-CO2 even more important
3. Aerosols Complicate the Story
If all pollution is reduced, how much will aerosol
cooling effect be altered?
How Can Climate be Stabilized?
Must Restore Planet’s Energy Balance
Modeled Imbalance: +0.75 ± 0.25 W/m2
Ocean Data Suggest: +0.5 ± 0.25 W/m2
Requirement Might be Met Via:
Reducing CO2 to 350 ppm or less
- and Reducing non-CO2 forcing ~ 0.25 W/m2
Are Needed Actions Feasible?
Coal must be phased out & Unconventional Fossil Fuels
avoided
Requires Carbon Tax & Dividend
‘Cap & Trade’ a Proven Failure
Do not lump non-CO2 forcings w/ CO2
Methane + Ozone most important (reduction feasible as
fossil fuel use declines)
Emphasize black carbon reductions among aerosols
The nature of our future environment depends strongly on which
“scenario” forecasters use.
The scenarios differ only in the extent of society’s effort to
conserve and reduce fossil-fuel use.
YOUR behavior
will determine how
badly Earth is
damaged.
Oil and power companies are not to blame for climate change.
We all are!!
CO2 Concentration in Ice Cores and
CO2 Concentration
in Ice Core
and
Atmospheric
CO2 Projection
for Samples
Next 100
Years
Projections for Next 100 Years
700
Projected
Projected
(2100) (2100)
650
600
Vostok Record
IPCC IS92a Scenario
Law Dome Record
Mauna Loa Record
500
We’re Living in A
No-Analog Zone
450
400
Current
(2001)
Current
(2001)
350
300
250
200
150
400,000
300,000
200,000
100,000
0
Years Before Present (BP 1950)
Source: C. D. Keeling and T. P. Whorf; Etheridge et.al.; Barnola et.al.; (PAGES / IGBP); IPCC
Challenges
of
a
Changing
Earth
—
July
2001
50
CO2 Concentration (ppmv)
550