Transcript Greenhouse Gases and Climate Change

Greenhouse Gases and Climate Change:
Global Changes and Local Impacts
Anthony J. Broccoli
Director, Center for Environmental Prediction
Department of Environmental Sciences
Rutgers University
New Jersey Clean Air Council
April 11, 2007
“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
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
Red, green, and blue lines
represent different
emissions scenarios.
Height of each colored bar
represents variations among
different climate models.
Potential Climate Change Impacts
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?
• 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).
Global mean sea level changes
Effects of Sea Level Rise on the Coastal Environment
Land area susceptible
to inundation
Land area susceptible
to coastal flooding
(“30-yr flood”)
50% probability of 0.61 m
sea level rise by 2100
1% probability of 1.22 m
sea level rise by 2100
Source: M. D. Beevers, U.S. Climate Change Science Program Workshop, Nov. 2005
Effects of Climate Change on Water Resources
Floods and Droughts?
Warmer
↓
More
Precipitation
Warmer
↓
More
Evaporation
“Increases in the amount of precipitation are very likely in highlatitudes, while decreases are likely in most subtropical land regions,
continuing observed patterns in recent trends.”
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.
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
Flood Stage
More Climate Change in the Pipeline
Future emissions
Additional “zero-emission”
warming (aka “commitment”)
Warming to date
Managing Climate Change
• Leadership: Raise public awareness of the challenges
posed by climate change and the need to mitigate and
adapt.
• Mitigation: Reduce emissions of carbon dioxide and
other greenhouse gases.
• Adaptation: Increase the resilience of society to
climate change.
• Knowledge: Develop a better understanding of the
details of future climate change.