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Is there really a global
warming happening?
Review of last lecture
• Air pollution. 2 categories
• 6 types of major pollutants: particulates, carbon oxides,
sulfur dioxides, nitrogen oxides, volatile organic
compounds, ozone
• Air quality index
• History of air pollution: The Medieval pollution, The 16th19th centuries, The 20th century, The 21st century
How is scientific consensus achieved
on global warming?
• The Intergovernmental Panel on Climate Change
(IPCC) is organized by the World Meteorological
Organization.
• This is a worldwide enterprise that includes literally
thousands of scientists that are involved in
producing and critiquing a definitive statement on
climate change. The political controversies have
centered around condensed summaries produced
for policy makers.
• We have had 4 assessments by IPCC so far. The
last one was completed in 2007, and the next is
scheduled for completion in summer 2013. Many of
the figures shown here are taken from the IPCC
2007 report.
How are human activities changing the
Earth’s environment?
• Release of greenhouse gases
• Release of aerosols
• Change of land cover
Human activities and the Earth’s environment
I: Release of greenhouse gases - Significant warming
Deuterium
(Temperature)
• Global atmospheric concentrations of CO2 and CH4 have increased
markedly as a result of human activities since 1750 and now far
exceed pre-industrial values determined from ice core
measurements spanning the last 650,000 years!
Radiative forcing of greenhouse gases
The global net effect of human activities since 1750 has been one of warming.
Sources of Greenhouse Gases (GHGs)
CO2 fossil fuel use is the dominant cause of CO2 increase
GHG Emissions by Sector
GHG emissions per capita
Human activities and the Earth’s environment
II: Release of aerosols - Slight cooling
Human activities and the Earth’s environment
III: Change of land cover - Slight cooling
Movie time
Weather: Heat
Observed Changes in Air Temperature:
Significant increases
Observed Changes in Temperature: Significant
increases throughout the troposphere and ocean
Mid to upper
troposphere
Lower
troposphere
Ocean
Observed Changes in Arctic Sea Ice:
Significant melting and positive feedback
Fom National Snow & Ice Data Center
Retreat of Greenland Ice Sheet – a huge contributor
to sea level rise today
Greenland is responsible for about 10% of the observed global sea level rise
and accelerating. Greenland holds 7 m of sea level equivalent.
From UNEP
Observed Changes in Snow Cover:
Significant melting
Retreat of Mountain Glaciers: a
major contributor to sea level rise
Glacier retreat is a world-wide phenomena.
Will affect water supply for millions:
• Kenya/Tanzania
• Northern India
• Andes Mountains
IPCC (2001)
Tropical glaciers
Peru's Quelccaya ice
cap is the largest in
the tropics. If it
continues to melt at
its current rate—
contracting more than
600 feet (182.8 meters)
a year in some
places—it will be gone
by 2100, leaving
thousands who rely
on its water for
drinking and
electricity high, dry,
and in the dark.
From National
Geographic
Observed Changes in Global Sea Level
Observed Changes in Sea Level
Largest in the western part of ocean basin
Observed Changes in Water Vapor
Significant increase
Observed Changes in Precipitation:
Significant change in many places
Change in Mean vs Change in Extremes
Observed changes in temperature extremes:
Less very cold nights and more very warm nights
Observed changes in precipitation extremes:
Increased contribution from very wet days
Summary
• 3 ways human activities affect the climate. Which one warms up (cools
down) the climate?
• Rapid increase of greenhouse gases (CO2, CH4, N2O) since 1750: far
exceed pre-industrial values determined from ice core measurements
spanning the last 650,000 years, which is mainly caused by CO2 fossil
fuel use.
• Radiation effect of greenhouse gases: warming.
• Observed change of mean: air temperature, ocean temperature,
melting of arctic sea ice, Greenland ice sheet, snow and glaciers, rising of
sea level.
• Observed change of extreme events: temperature, precipitation