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Global Change
Topic 7 Part 1
The Earth Greenhouse


NPS
Naturally ©
occurring
CO2, H2O, N2O, and CH4 help to keep the earth warm. This
supports life.
The problem: humans produce lots more of these gases than naturally occur, plus
CFCs and tropospheric ozone. This is trapping more heat than would occur naturally
at this point.
Greenhouse gases
Other factors that affect the earth's temperature




Oceans
Cloud cover
Air pollution levels
Photosynthesis levels
Volcanoes and climate
Historic climate
The Medieval Warming
Historic Temperature and CO2 Proxies



Species composition
Ice cores
Oxygen isotope ratios
Foraminifera
Trends in greenhouse gas concentrations
Sun
Carbon (and some heat) sources and sinks
Troposphere
Aerosols
Greenhouse
gases
Cooling
from
increase
Warming
from
decrease
CO2
removal
by plants
and
soil
organisms
CO2 emissions
from land
clearing,
fires, and decay
Heat and
CO2 removal
Heat and
CO2
emissions
Ice and snow cover
Shallow ocean
Land and soil biota
Natural and human emissions
Long-term
storage
Deep ocean
Fig. 20-6, p. 469
Current trends
Earth is getting warmer: the temperature has been well above normal
for more than 25 years.
Current trends
Grinnell Glacier, Glacier National Park 1900 and 2008
Snow and ice are melting at rates unseen for thousands of years. In
Glacier National Park, for example, there were 150 glaciers in 1850.
Today, there are 26.
Current trends
Arctic ice in the summer
Sea ice is dwindling, especially in the Northern Hemisphere. Satellites
have seen average Arctic sea ice shrink by 2.7% per decade from 1978
to 2006, with faster melting in summer.
Positive feedback loops increase warming



Melting of polar
sea ice
Melting of glaciers
Shorter winters in
the tundra
(methane release)
Negative feedback loops can temporarily
slow warming
Predictions
Climate change effects
Rising Sea Levels
Species range and
seasonal behavior shifts


Some bird species are
already showing shifts in
seasonal habits.
Other early signs:




Plants are flowering early
than normal, some
pollinators are missing
out
Some insects are
emerging before bird
eggs hatch
Plankton are shifting
ranges, affecting the rest
of their food chains
Increased ocean acidity,
degradation of coral reefs
Climate change: impacts on people




In a warmer world, agricultural productivity may
increase in some areas and decrease in others.
Crop and fish production in some areas could be
reduced by rising sea levels that would flood
river deltas.
Reduce drinking water supplies
Global warming will likely increase deaths from:
 Heat and disruption of food supply.
 Spread of tropical diseases to temperate
regions.
 Increased number of environmental refugees.