Transcript PPT - Earth and Atmospheric Sciences

What role does the Ocean
play in Global Climate
Change?
The Global Greenhouse
How the Greenhouse Effect Works
Emission Spectra of Sun and Earth and
Absorption Spectra of Atmosphere
Interplanetary Comparisons:
Venus: Higher concentrations: 400o C
Mars: Lower concentrations: -50o C
Intergovernmental Panel on Climate Change
(IPCC)
• Established by the UN and World Meteorological Organization in
1988
• Mission of the IPCC: to assess the scientific, technical, and socioeconomic information relevant for the understanding of the
risks of human-induced climate change
• 2,500 of the world’s leading climate scientists and technical
experts contribute to reports
• Provides comprehensive and balanced assessments of climate
change science, impacts, and adaptation and mitigation
options
• Extensive peer-review and governmental review ensures scientific
credibility and policy relevance
Observed Changes in Greenhouse Gas
Concentrations
Predicted Increases in CO2 Emissions and
Concentrations (from IPCC SAR 1995)
Global Temperature and Atmospheric
CO2 over Geological Time
• Current level of CO2 is outside
bounds of natural
variability
• Rate of change of CO2 is also
unprecedented
• Clear correlation between
atmospheric CO2 and
temperature over last
160,000 years
Observed Changes in Global Mean Temperature
(measured and proxy data)
*relative to 1961-1990 average
IPCC Global Mean
Temperature Predictions:
• Global average temperature is
projected to increase by
1.5 to 5.5° C (2.5 to 10.4° F)
from 1990 to 2100
• Projected temperature increases in
TAR are greater than those
in SAR.
• Projected rate of warming is
unprecedented for last
10,000 years
Predicted Temperature Change
in the Context of Last 1000 Years
• 1861 to 2000:
Instrumental data
• 1000 to 1861:
Proxy data
• 2000 to 2100:
Model projections
Observed Changes in Spatial Patterns of Land
and Sea Surface Temperature
Surface temperature change between 20 year mean
1955-1974 and 20 year mean 1975-1994
Predicted Changes in Spatial Patterns of Land
and Sea Surface Temperature
Model-predicted surface temperature change by 2050
Atmospheric CO2 and Sea Level Rise
IPCC Global Sea Level Rise Predictions:
• Global average sea level is
projected to rise by 10 to
80 cm (4 to 35 inches)
between 1990 and 2100
• Projected rise is slightly lower
than the range presented
in the SAR.
• Sea level will continue to rise
for hundreds of years
after stabilization of
greenhouse gas
concentrations
Components of Sea Level Rise
• Thermal expansion and land ice melt after an initial 1% increase in CO2
for 70 years
• Eventually. most of sea-level rise will be due to thermal expansion of ocean,
not melting of ice
Predicted Changes in Annual Precipitation by 2050
The projected change is compared to the present day with a ~1% increase per year in equivalent CO 2
Increase in Extreme Precipitation
Events in the U.S.
Number of Billion Dollar Weather Disasters
7
6
5
4
Events
3
2
1
0
80
82
84
86
88 90
Year
92
94
96
98
Extreme Weather Events
Change in Phenomenon
Confidence in projected change*
Higher maximum temperatures,
more hot days
Very likely
Higher minimum temperatures,
fewer cold days and frost days
Very likely
Increase of heat index
Very likely, over most areas
More intense precipitation events
Very likely, over many areas
Increased summer continental
drying & associated risk of drought
Increase in tropical cyclone peak
wind and precipitation intensities
Likely, over most mid-latitude
continental interiors
Likely, over some areas
*Judgmental estimates of confidence by IPCC: very likely - 90-99% chance,
likely - 66-90% chance.
Impacts of Climate Change
on Insurance
•
•
•
•
Economic losses from catastrophic weather events
have increased 10-fold in recent decades
Increasing losses are due in part to socioeconomic
factors and in part to climatic factors
Because of expensive coastal development and
projection of more extreme events - insurance
damages, claims, and costs are likely to increase
Significant challenges in the future if high impact
events occur or if catastrophes are closelyspaced
IPCC Policy-Makers Summary:
Observations
• Human activities are changing the atmospheric concentrations
of greenhouse gases.
• Extensive and wide-spread evidence that the earth has warmed
0.3 - 0.6° C over the last century; however, this warming
has not been uniform.
• Global sea level has risen 10 – 20 cm over the last century.
Forecasts
• Global average temperature is projected to increase by 1.5 to
5.5° C (2.5 to 10.4° F) from 1990 to 2100
• Global average sea level is projected to rise by 10 to 80 cm
(4 to 35 inches) between 1990 and 2100
• Likely to be an increase in extreme weather events
IPCC History: Evolution of
Our Knowledge
•
FAR (1990): “The size of the warming is broadly
consistent with predictions of climate models, . . . but
the unequivocal detection of the enhanced greenhouse
effect from observations is not likely for a decade or
more.”
•
SAR (1996): “The balance of evidence suggests a
discernible human influence on climate.”
•
TAR (2001): “There is new and stronger evidence that
most of the warming observed over the last 50 years is
attributable to human activities.”
Unpredictability: What if our
models are not complete?
Greater warming, lesser
warming, but what about
cooling?
Example: Shutdown of NADW Formation
and Collapse of Ocean Thermohaline
Circulation?