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Global Warming: It’s Later Than We
Think…But It’s Not Too Late
Anthony J. Broccoli
Director, Center for Environmental Prediction
Department of Environmental Sciences
Rutgers University
Pulse of the Planet Lecture Series
Liberty Science Center, Jersey City, NJ
January 26, 2008
Temperatures in the New York City area
in the past 30 days have been:
a) more than 2°F below normal
b) within 1°F of normal
c) about 3°F above normal
d) more than 6°F above normal
Temperatures in the New York City area
in the past 30 days have been:
a) more than 2°F below normal
b) within 1°F of normal
c) about 3°F above normal
d) more than 6°F above normal
Source: NOAA Climate Prediction Center
Source: NOAA Climate Prediction Center
“The unequivocal detection of the enhanced greenhouse effect
from observations is not likely for a decade or more.”
Climate Change – The IPCC Scientific Assessment (1990)
“The balance of evidence suggests
a discernible human influence on global climate.”
Climate Change 1995 – The Second Assessment of the
Intergovernmental Panel on Climate Change (IPCC)
“Most of the observed warming over the last 50 years is likely to
have been due to the increase in greenhouse gas concentrations.”
Climate Change 2000 – The Third Assessment Report of the IPCC
“Most of the observed increase in globally averaged
temperatures since the mid-20th century is very likely due to
the observed increase in anthropogenic greenhouse gas
concentrations.”
Climate Change 2007 – The Fourth Assessment Report of the IPCC
The IPCC’s conclusion that the observed
warming is very likely due to increasing
greenhouse gases an that further
warming is on the way is based on:
a) laboratory measurements
b) results from computer models
c) climate observations
d) all of the above
The IPCC’s conclusion that the observed
warming is very likely due to increasing
greenhouse gases an that further
warming is on the way is based on:
a) laboratory measurements
b) results from computer models
c) climate observations
d) all of the above
What Are Climate Models?
“It is extremely unlikely that global climate change of the past
fifty years can be explained without external forcing.”
Blue: Natural
Pink: Natural + Human-induced
Projections of Future Climate
Variations among colored lines
represents uncertainty due to
uncertainty in future emissions.
Simulating Future Climate Change
Source: NOAA Geophysical Fluid Dynamics Laboratory
Potential Climate Change Impacts
Global Impacts of Climate Change
Report by IPCC Working Group II on Impacts, Adaptation and
Vulnerability was released on 6 April 2007. Some of the
highlights from this report:
• There will be some winners, but more losers
• Densely populated coastal regions will face increased
pressures from sea level rise and more extreme weather
• Poor communities and stressed ecosystems will suffer most, as
they are already living “on the edge”
• 60% of world’s species are already responding to change
Global Impacts of Climate Change
Report by IPCC Working Group II on Impacts, Adaptation and
Vulnerability was released on 6 April 2007. Some of the
highlights from this report:
• There will be some winners, but more losers
• Densely populated coastal regions will face increased
pressures from sea level rise and more extreme weather
• Poor communities and stressed ecosystems will suffer most, as
they are already living “on the edge”
• 60% of world’s species are already responding to change
Sea Level Trends in New Jersey
Atlantic City, NJ
Source: National Oceanic and Atmospheric Administration
NJ sea level rise
0.4 m/century
= global sea level rise + other effects
= 0.16 m/century
+ 0.24 m/century
Why is global sea level rising?
a) the density of the ocean is
decreasing
b) sea ice is melting rapidly
c) mountain glaciers are melting
d) the Greenland and Antarctic ice
sheets are melting
Why is global sea level rising?
a) the density of the ocean is
decreasing
b) sea ice is melting rapidly
c) mountain glaciers are melting
d) the Greenland and Antarctic ice
sheets are melting
Why Is Global Sea Level Rising?
• Thermal expansion
Warmer water is less dense
than colder water.
• Melting of glaciers and ice
caps
Water released by the melting
of ice on land adds to the
volume of the oceans.
• Melting and calving of
Greenland and Antarctic
ice sheets
Depends on the ice sheet
dynamics (how the ice flows).
Why Is Global Sea Level Rising?
• Thermal expansion
Warmer water is less dense
than colder water.
• Melting of glaciers and ice
caps
Water released by the melting
of ice on land adds to the
volume of the oceans.
• Melting and calving of
Greenland and Antarctic
ice sheets
Depends on the ice sheet
dynamics (how the ice flows).
Why Is Global Sea Level Rising?
• Thermal expansion
Warmer water is less dense
than colder water.
• Melting of glaciers and ice
caps
Water released by the melting
of ice on land adds to the
volume of the oceans.
• Melting and calving of
Greenland and Antarctic
ice sheets
Depends on ice sheet
dynamics (how the ice flows).
Effects of Sea Level Rise on the Coastal Environment
Land area susceptible
to inundation
Land area susceptible
to coastal flooding
(“30-yr flood”)
0.61 m (2 ft) sea level
rise by 2100—middle of
the road estimate.
1.22 m (4 ft) sea level
rise by 2100—more melting
from Greenland/Antarctica
Source: M. D. Beevers, U.S. Climate Change Science Program Workshop, Nov. 2005
“Ash Wednesday Storm”
Harvey Cedars, March 1962
New Brunswick, April 16, 2007
John Munson/The Star-Ledger
3 of 7 largest floods
since 2004
Flood Stage
Warmer
↓
More
Precipitation
Warmer
↓
More
Evaporation
“…there is an increased chance of intense precipitation
and flooding due to the greater water-holding capacity
of a warmer atmosphere. This has already been
observed and is projected to continue because in a
warmer world, precipitation is concentrated into more
intense events…” IPCC Fourth Assessment, 2007
New Brunswick, April 16, 2007
John Munson/The Star-Ledger
days per year over 100ºF
days per year over 90ºF
IPCC: “It is very likely that hot extremes, heat waves, and heavy
precipitation events will continue to become more frequent.”
Changes in number of days with heat waves
from UCS Northeast Climate Impacts Assessment
Future Emissions Scenarios
All scenarios show
increasing emissions
during next several
decades
Some scenarios show
decreased emissions
in latter half of 21st
century
Even with aggressive
reductions in emissions,
CO2 would rise to 2x
preindustrial levels
More Warming in the Pipeline
Future emissions
Additional “zero-emission”
warming (aka “commitment”)
Warming to date
Psychological Barriers?
• Climate change is not the result of malevolence.
• Climate change does not violate our moral
sensibilities (i.e., cultural taboos).
• Climate change is perceived as a future rather than
an immediate threat.
• Climate change proceeds gradually.
Source: Daniel Gilbert, Harvard University, Los Angeles Times, July 2006
What actions would you favor for
reducing the threat of climate change?
a) increase energy efficiency
b) capture and sequester CO2 from fossil
fuel burning
c) increase nuclear power generation
d) build more wind turbines and solar
power systems
What actions would you favor for
reducing the threat of climate change?
a) increase energy efficiency
b) capture and sequester CO2 from fossil
fuel burning
c) increase nuclear power generation
d) build more wind turbines and solar
power systems
“Wedges”
Billion of Tons of
Carbon Emitted per
Year
14
14 GtC/y
Seven “wedges”
Historical
emissions
7
Flat path
O
7 GtC/y
1.9 
0
1956
2006
2056
Source: S. Pacala and R. Socolow, Princeton Univ.
2106
15 Different Technologies Already in the
Marketplace at Industrial Scale
Coal to Gas
Natural Sinks
CCS
Nuclear
Efficiency
Renewables
The Global Warming Dilemma
(J. Mahlman, In Solutions for an Environment in Peril, 2002)
“There are no quick policy fixes, nationally or globally. If we
don't begin to chip away at the problem soon, it is very likely
that serious consequences will be wired in for the world of our
great-grandchildren and for their great-grandchildren....
The long time scales and robustness of the problem almost
guarantees that our descendants in the 22nd century will, with
historical perspective, see that we were actually confronted
with a major planet-scale stewardship/ management problem.
They will most assuredly note how we responded, or how we
did not respond to the problem.”
The climate is
changing…
Why Is Global Sea Level Rising?
Melting Glaciers
and Ice Caps:
Water released by
the melting of
ice on land
adds to the
volume of the
oceans.
Global Warming and the Hydrologic Cycle
• The downward flux of radiative energy (i.e., sunlight and
infrared radiation) at the surface is balanced by evaporation
and sensible heating of the atmosphere.
• If the downward flux of energy increases, then evaporation
will increase.
• On a global basis, evaporation and precipitation must
balance.
• Thus as the earth warms, both evaporation and
precipitation will increase.
Warmer
↓
More
Precipitation
Warmer
↓
More
Evaporation
Detection
Attribution
Likelihood that trend
occurred in late 20th
century (typically
post 1960)
Likelihood of a human
contribution to
observed trend
Likelihood of future
trends based on
projections for 21st
century using SRES
scenarios
Warmer and fewer cold days
and nights over most land
areas
Very likely
Likely
Virtually certain
Warmer and more frequent
hot days and nights over most
land areas
Very likely
Likely (nights)
Virtually certain
Warm spells / heat waves.
Frequency increases over most
land areas
Likely
More likely than not
Very likely
Heavy precipitation events.
Frequency (or proportion of
total rainfall from heavy falls)
increases over most areas
Likely
More likely than not
Very likely
Area affected by droughts
increases
Likely in many regions
since 1970s
More likely than not
Likely
Intense tropical cyclone
activity increases
Likely in some regions
since 1970
More likely than not
Likely
Increased incidence of
extreme high sea level
(excludes tsunamis)
Likely
More likely than not
Likely
Phenomenon and
direction of trend
Projection
Rahmstorf, Stefan, et al., 2007: Recent
climate observations compared to
projections. Science.
Published online 2 February 2007,
10.1126/science.1136843
Dashed lines and gray shading are
2001 TAR projections. Colored lines
are observations. While CO2 is
increasing as projected, temperature is
increasing a little more than all the
scenarios.
“Sea level closely follows the upper
gray dashed line, the upper limit
referred to by IPCC as ‘including landice uncertainty.’ Note that the rate of
rise for the last 20 years of the
reconstructed sea level is 25% faster
than the rate of rise in any 20 year
period in the preceding 115 years.”
Global mean sea level changes
Changes in Heat Index
•
•
•
The heat index combines the
effects of temperature and
humidity to estimate human
comfort.
Results are from simulations with
three global climate models with
two emissions scenarios,
representing the low and high
ends of the IPCC range.
Under the high emissions
scenario, Tri-State summers at
the end of the 21st century are
projected to be similar to those in
Savannah, Georgia today.
Simulated Changes in Precipitation
Relative changes in precipitation (%) for the period 2090–2099, relative to 1980–1999.
Stippled areas are where more than 90% of the models agree in the sign of the change.
Increased frequency of heavy precipitation events over most areas: Very likely
More areas affected by drought: Likely